The Atmospheric Dynamics Mission ADM-Aeolus will make direct measurements of global wind-fields. The aim is to provide global observations of wind profiles with a vertical resolution that will satisfy the requirements of the World Meteorological Organization.

The only payload is the Atmospheric Laser Doppler Instrument (ALADIN), a direct detection Doppler lidar operating in the UV. It will determine the wind velocity component normal to the satellite velocity vector. These wind profile measurements will be assimilated into numerical forecasting models to improve the quality of the global three-dimensional wind fields. To make full use of the data, the global wind profile data must be made available to the weather prediction centers in near real time.

EADS-Astrium (UK and France) and their subcontractors develop Aeolus and ALADIN. Most subsystems have been completed, and the assembly of the Flight Model is well under way, and proceeding to a launch envisaged in late 2008. Details of ALADIN and several of its subsystems are reported in various papers of this conference.

This paper presents a summary of the phase-0 performed in 2005 for the Pegase mission. The main scientific goal is the spectroscopy of hot Jupiters (Pegasides) and brown dwarfs from 2.5 to 5 μm. The mission can extend to the exploration of the inner part of protoplanetary disks, the study of dust clouds around AGN,... The instrument is basically a two-aperture (D=40 cm) interferometer composed of two siderostats and one beam-combiner. The formation is linear and orbits around L2, pointing in the anti-solar direction within a +/-30° cone. The baseline is adjustable from 50 to 500 m in both nulling and visibility measurement modes. The angular resolution ranges from 1 to 20 mas and the spectral resolution is 60. in the nulling mode, a 2.5 nm rms stability of the optical path difference (OPD) and a pointing stability of 30 mas rms impose a two level control architecture. It combines control loops implemented at satellite level and control loops operating inside the payload using fine mechanisms. According to our preliminary study, this mission is feasible within an 8 to 9 years development plan using existing or slightly improved space components, but its cost requires international cooperation. Pegase could be a valuable Darwin/TPF-I pathfinder, with a less demanding, but still ambitious, technological challenge and a highly associated scientific return.

The Atmospheric LAser Doppler INstrument (ALADIN) is the payload of the ADM-AEOLUS mission, which aims at measuring wind profiles as required by climatology and meteorology users. ALADIN belongs to a new class of Earth Observation payloads and will be the first Wind Lidar in space. The instrument comprises a high energy laser and a direct detection receiver operating on aerosol and molecular backscatter signals in parallel.

ALADIN is now in its final construction stage: the Opto-Structural-Thermal-Model (OSTM) has been completed and successfully tested, mo st of the flight equipments have been delivered and the integration of Flight Model (FM) has started. The Aeolus satellite is developed for the European Space Agency with EADS Astrium as prime contractor for the satellite and the instrument.

The European Space Agency is developing its first spaceborne LIDAR for global monitoring of wind velocities. ALADIN, to be launched on board ADMAeolus in 2008, is a pulsed Nd:YAG laser with about 120 mJ of pulse energy at 355 nm and a repetition rate of 100 Hz during bursts. Within the projected mission duration of three years, this gives a lifetime requirement of close to 5 billion pulses.

While laser-induced damage thresholds of optics in vacuum (possibly contaminated by small amounts of organic compounds) can differ from atmospheric conditions, their damage behaviour is generally poorly understood. The European Space Agency has therefore established a test campaign to measure the power handling of all the instrument optics with several European laboratories participating.

In the Optics and Opto-Electronics laboratory at ESTEC, a laser-induced damage threshold (LIDT) test facility has been set up with a 50 Hz Nd:YAG test laser. The pulse energy is 700 mJ at 1064 nm. This allows us to recreate the laser pulse conditions to which the ALADIN optics will be exposed. The flattop beam profile of the test laser irradiates the optics with uniform fluences and relatively large spots (up to 1mm across) at damaging intensities.

Damage tests are performed with up to 1 million pulses per test spot according to the S-on-1 test ISO-11254 standard, requiring typically 10 days to test one sample. With such extended tests, we can predict the laser-induced damage threshold over the ALADIN lifetime with improved accuracy.

Selected technologies for the integration of the TRANSMIT/RECEIVE OPTICS (TRO) are presented. One of the challenging characteristics of the TRO is its stringent requirement on opto-mechanical stability. The stability performance of the TRO must be ensured for the relevant interface environments (thermal, structural) over the 3 years mission lifetime. Comprehensive analyses have been conducted, which have confirmed the need for the development of special integration technologies. Also, dedicated test equipment has been developed to precisely verify the TRO´s optomechanical stability. Another important feature of the TRO is its exposure to the high power laser beam of the ADALIN instrument. The corresponding optical elements and their mounts must survive exposure to light intensities up to the required laser-induced damage thresholds (LIDT). Two types of adhesives for gluing of the TRO optics have been selected. Their qualification w.r.t. outgassing was necessary since LIDT´s of optical surfaces are significantly reduced when organic outgassing products are deposited there.

The operational deployment of MSG-1 at the beginning of 2004, the first of a series of four Meteosat Second Generation (MSG) satellites, marks the start of a new era in Europe for the meteorological observations from the geostationary orbit. This new system shall be the backbone of the European operational meteorological services up to at least 2015. The time required for the definition and the development of new space systems as well as the approval process of such complex programs implies to plan well ahead for the future missions. EUMETSAT have initiated in 2001, with ESA support, a User Consultation Process aiming at preparing for a future operational geostationary meteorological satellite system in the post-MSG era, named Meteosat Third Generation (MTG). The first phase of the User Consultation Process was devoted to the definition and consolidation of end user requirements and priorities in the field of Nowcasting and Very Short Term Weather Forecasting (NWC), Medium/Short Range global and regional Numerical Weather Prediction (NWP), Climate and Air Composition Monitoring and to the definition of the relevant observation techniques.

After an initial post-MSG mission study (2003-2004) where preliminary instrument concepts were investigated allowing in the same time to consolidate the technical requirements for the overall system study, a MTG pre-phase A study has been performed for the overall system concept, architecture and programmatic aspects during 2004-2005 time frame.

This paper provides an overview of the outcome of the MTG sensor concept studies conducted in the frame of the pre-phase A. It namely focuses onto the Imaging and Sounding Missions, highlights the resulting instrument concepts, establishes the critical technologies and introduces the study steps towards the implementation of the MTG development programme.

The proposed Canadian Hyperspectral Environment and Resources Observer (HERO) mission is described.

The activities described in this paper have been developed in the frame of the EUCLID CEPA 9 RTP 9.9 “High Resolution Optical Satellite Sensor” project of the WEAO Research Cell. They have been focused on the definition of an interferometric instrument optimised for the high-resolution optical surveillance from geostationary orbit (GEO) by means of the synthetic aperture technique, and on the definition and development of the related enabling technologies. In this paper we describe the industrial team, the selected mission specifications and overview of the whole design and manufacturing activities performed.

For very large telescope diameters, typically above 4 meters, monolithic telescopes can hardly be envisaged for space applications. Optical aperture synthesis can be envisaged in the future for improving the image resolution from high altitude orbits by co-phasing several individual telescopes of smaller size and reconstituting an aperture of large surface. The telescopes can be deployed on a single spacecraft or distributed on several spacecrafts in free flying formation. Several future projects are based on optical aperture synthesis for science or earth observation. This paper specifically discusses the limitations and interest of aperture synthesis technique for Earth observation from high altitude orbits, in particular geostationary orbit. Classical Fizeau and Michelson configurations are recalled, and system design aspects are investigated: synthesis of the Modulation Transfer Function (MTF), integration time and imaging procedure are first discussed then co-phasing strategies and instrument metrology are developed. The discussion is supported by specific designs made at EADS Astrium. As example, a telescope design is presented with a surface of only 6.6 m² for the primary mirror for an external diameter of 10.6 m allowing a theoretical resolution of 1.2 m from geostationary orbit with a surface lower than 10% of the overall surface. The impact is that the integration time is increasing leading to stringent satellite attitude requirements. Image simulation results are presented. The practical implementation of the concept is evaluated in terms of system impacts in particular spacecraft attitude control, spacecraft operations and imaging capability limitations.

A breadboard set-up has demonstrated a concept of cophasing and co-alignment based on an external reference source for synthetic aperture telescopes applications. These types of systems can be extremely valuable in order to perform coarse re-alignment of synthetic aperture telescope, following thermo-elastic deformation and deployment effects in space flight environments.

In this paper, we describe Optical Aperture Synthesis (OAS) imaging instrument concepts studied by Alcatel Alenia Space under a CNES R&T contract in term of technical feasibility. First, the methodology to select the aperture configuration is proposed, based on the definition and quantification of image quality criteria adapted to an OAS instrument for direct imaging of extended objects. The following section presents, for each interferometer type (Michelson and Fizeau), the corresponding optical configurations compatible with a large field of view from GEO orbit. These optical concepts take into account the constraints imposed by the foreseen resolution and the implementation of the co-phasing functions. The fourth section is dedicated to the analysis of the co-phasing methodologies, from the configuration deployment to the fine stabilization during observation. Finally, we present a trade-off analysis allowing to select the concept wrt mission specification and constraints related to instrument accommodation under launcher shroud and in-orbit deployment.

This paper describes energetic, spatial, temporal and spectral characterization measurements of the Engineering Qualification Model (EQM) of the Laser Transmitter Assembly (TXA) used in the ALADIN instrument currently under development for the ESA ADM-AEOLUS mission (EADS Astrium as prime contractor for the satellite and the instrument). The EQM is equivalent to the Flight Model, with the exception of some engineering grade components. The Laser Transmitter Assembly, based on a diode pumped tripled Nd:YAG laser, is used to generate laser pulses at a nominal wavelength of 355 nm. This laser is operated in burst mode, with a pulse repetition cycle of 100 Hz during bursts. It is capable to operate in Single Longitudinal Mode and to be tuned over 25 GHz range. An internal “network” of sensors has been implemented inside the laser architecture to allow “in flight” monitoring of transmitter. Energy in excess of 100 mJ, with a spatial beam quality factor (M²) lower than 3, a spectral linewidth less than 50 MHz with a frequency stability better than 4 MHz on short term period have been measured on the EQM. Most of the obtained results are well within the expected values and match the Instrument requirements. They constitute an important achievement, showing the absence of major critical areas in terms of performance and the capability to obtain them in a rugged and compact structure suitable for space applications. The EQM will be submitted in the near future to an Environmental test campaign.

A number of space missions (including in the ESA Exploration Programme) foreseen a use of laser radar sensor (or lidar) for determination of range between spacecrafts or between spacecraft and ground surface (altimetry). Such sensors need to be compact, robust and power efficient, at the same time with high detection performance. These requirements can be achieved with a Pseudo-Random Noise continuous wave lidar (PRN cw lidar). Previous studies have pointed to the advantages of this lidar with respect to space missions, but they also identified its limitations in high optical background.

The progress of the lasers and the detectors in the near IR spectral range requires a re-evaluation of the PRN cw lidar potential. Here we address the performances of this lidar for surface detection (altimetry) in planetary missions. The evaluation is based on the following system configuration: (i) A cw fiber amplifier as lidar transmitter. The seeding laser exhibits a single-frequency spectral line, with subsequent amplitude modulation. The fiber amplifier allows high output power level, keeping the spectral characteristics and the modulation of the seeding light input. (ii) An avalanche photodiode in photon counting detection; (iii) Measurement scenarios representative for Earth, Mercury and Mars.

This work presents a new technological concept for large aperture, lightweight, telescopes using thin deployable active mirrors, currently under a feasibility study for spaceborne Lidars.

The study is mainly addressed to a DIAL (Differential Absorption Lidar) at 935.5 nm for the measurement of water vapour profile in atmosphere, to be part of a typical small ESA Earth Observation satellite to be launched with ROCKOT vehicle. A detailed telescope optical design will be presented, including the results of angular and spatial resolution, effective optical aperture and radiometric transmission, optical alignment tolerances, stray-light and baffling. Also the results of a complete thermo-mechanical model will be shown, discussing temporal and thermal stability, deployment technology and performances, overall mass budget, technological and operational risk and system complexity.

In a project with the Canadian Space Agency (CSA), we have developed prototypes of 1.55 μm frequencystabilized lasers for space applications. These lasers can be used as metrology sources for internal calibration of spectrometers such as the Cross-track Infrared Sounder (CrIS). Our prototypes include a 1552 nm DFB laser frequency-locked to H¹³CN using external phase modulation. The prototypes feature high quality characteristics such as CW output power of 8 mW and a narrow linewidth of 1.5 MHz. The frequency of the laser is known to a few ppm. The frequency stability levels at 10^-10 between 30 and 10 000 s. The relative intensity noise (RIN) falls from -100 to -140 dBc/Hz between 1 Hz and 10 kHz, and levels at -140 dBc/Hz between 10 kHz and 1 MHz. Further improvement to reduce the linewidth to a few kHz can be provided using an all-fiber interferometer and correction of the laser injection current accordingly.

Future LIDAR and range-finding missions in space require high-energy pulsed lasers. Typical concepts require a pump laser in the NIR spectral range, which is frequency-converted to the requested wavelength by external measures. We propose a novel master-oscillator power-amplifier (MOPA) concept capable to deliver 500- mJ pulses of about 10 ns pulse width at a pulse repetition frequency of 100 Hz. The output at 1064 nm is singlefrequency, linearly polarized, and exhibits high beamquality.

The ESA Darwin mission is primarily devoted to the detection of earth-like exoplanets and the spectroscopic characterization of their atmospheres for key tracers of life. Darwin is implemented as a free-flying stellar interferometer operating in the 6.5-20 micron wavelength range, and passively cooled to 40 K. The stellar flux is suppressed by destructive interference (nulling) over the full optical bandwidth. The planetary signal is extracted from the zodiacal background signature by modulating the optical response of the interferometer. The Darwin mission concept has evolved considerably in the past years. The original concept, based on six 1.5 m telescopes, has been replaced by more efficient designs using three to four three-meter class apertures. A novel 3D architecture is being evaluated, together with the conventional planar one, bearing the potential for significant volume and mass savings and enhanced straylight rejection. A number of technology development activities have been successfully completed, including optical metrology, optical delay lines, and single-mode infrared optical fibers. A second iteration of the Darwin System Assessment Study has been kicked off end 2005, aiming to consolidate the overall mission architecture and the preliminary design of the Darwin mission concept. This paper illustrates the current status of the Darwin mission, with special emphasis on the optical configuration and the technology development programme in the area of optics.

The European DARWIN mission aims at the detection of Earth-like exo-planets and at the spectroscopic characterization of their atmospheres. By nulling interferometry in the mid-infrared wavelength regime the stellar flux may be rejected. By spatial and temporal modulation of the interferometer’s receive characteristic the planet signal may be extracted from the background signals. The DARWIN instrument consists of a flotilla of free-flying spacecraft, three to four spacecraft carrying the collector telescopes and one spacecraft carrying the control units and the beam recombination and detection unit. We present different system design concepts for the DARWIN instrument which have been elaborated within the DARWIN System Assessment Study. We discuss various aperture configurations and beam routing schemes as well as modulation methods and and beam recombination schemes.

TNO, in cooperation with Micromega-Dynamics, SRON, Dutch Space and CSL, has designed a compact breadboard cryogenic delay line (figure 1) for use in future space interferometry missions. The work is performed under ESA contract 17.747/03 in preparation for the DARWIN mission. The breadboard (BB) delay line is representative of a flight mechanism. The delay line has a single stage voice coil actuator for Optical Path Difference (OPD) control, driving a twomirror cat’s eye. Magnetic bearings provide frictionless and wear free operation with zero-hysteresis. The design of the BB delay line has been completed.

The development test program, including operation at 100 K has been completed. The verification test programme is currently being carried out and will include functional testing at 40 K.

The objective of the so-called fringe sensor DWARF - derived from DARWIN AstRonomical Fringe Sensor is to measure all relevant perturbations and to provide real time control data to achieve co-phasing of the freeflying telescopes of the DARWIN system. An overview of the design of the sensor Breadboard (BB), as it has been designed and built at Kayser-Threde as Prime with main partners ONERA and Alcatel Space under ESA contract 17012/03/NL/EC is presented. An extensive test campaign has been carried out at ONERA. The respective optical test setup is outlined and the achieved performances for retrieval of primary and higher order aberrations are presented. As final outcome of the BB study the essential elements to build a fringe sensor (FS) flight model are shortly characterized and the respective development roadmap is sketched.

PEGASE, a spaceborne mission proposed to the CNES, is a 2-aperture interferometer for nulling and interferometric imaging. PEGASE is composed of 3 free-flying satellites (2 siderostats and 1 beam combiner) with baselines from 50 to 500 m. The goals of PEGASE are the spectroscopy of hot Jupiter (Pegasides) and brown dwarves, the exploration of the inner part of protoplanetary disks and the validation in real space conditions of nulling and visibility interferometry with formation flying.

During a phase-0 study performed in 2005 at CNES, ONERA and in the laboratories, the critical subsystems of the optical payload have been investigated and a preliminary system integration has been performed. These subsystems are mostly the broadband (2.5-5 μm) nuller and the cophasing system (visible) dedicated to the real-time control of the OPD/tip/tilt inside the payload. A laboratory breadboard of the payload is under definition and should be built in 2007.

The European Space Agency has approved Gaia, the sixth cornerstone mission of its Scientific Programme, and awarded the satellite development contract to EADS Astrium SAS at beginning of 2006 for its Implementation Phase.

The Gaia mission will provide unprecedented stellar position and radial velocity measurements. This will be used to produce a three-dimensional map of about one billion stars in our Galaxy and beyond. The most prominent feature of the Gaia satellite is the high precision payload, which is fully developed by EADS Astrium SAS. The paper is devoted to the payload description.

The Laser Metrology and Optic Active Control (LM&OAC) program has been carried out under ESA contract with the purpose to design and validate a laser metrology system and an actuation mechanism to monitor and control at microarcsec level the stability of the Basic Angle (angle between the lines of sight of the two telescopes) of GAIA satellite. As part of the program, a breadboard (including some EQM elements) of the laser metrology and control system has been built and submitted to functional, performance and environmental tests. In the followings we describe the mission requirements, the system architecture, the breadboard design, and finally the performed validation tests. Conclusion and appraisals from this experience are also reported.

Global astrometry, very demanding in term of stability, requires extremely stable material for optical bench. CeSiC developed by ECM and Alcatel Alenia Space for mirrors and high stability structures, offers the best compromise in term of structural strength, stability and very high lightweight capability, with characteristics leading to be insensitive to thermo-elastic at cryogenic T°. The HSOB GAIA study realised by Alcatel Alenia Space under ESA contract aimed to design, develop and test a full scale representative High Stability Optical Bench in CeSiC. The bench has been equipped with SAGEIS-CSO laser metrology system MOUSE1, Michelson interferometer composed of integrated optics with a nm resolution. The HSOB bench has been submitted to an homogeneous T° step under vacuum to characterise the homothetic behaviour of its two arms. The quite negligible inter-arms differential measured with a nm range reproducibility, demonstrates that a complete 3D structure in CeSiC has the same CTE homogeneity as characterisation samples, fully in line with the GAIA need (1pm at 120K). This participates to the demonstration that CeSiC properties at cryogenic T° is fully appropriate to the manufacturing of complex highly stable optical structures. This successful study confirms ECM and Alcatel Alenia Space ability to define and manufacture monolithic lightweight highly stable optical structures, based on inner cells triangular design made only possible by the unique CeSiC manufacturing process.

The present LISA (Laser Interferometer Space Antenna) gravitational wave detector concept features three satellites in individual earth trailing helio-centric orbits, which are linked by bi-directional monostatic laser interferometry between free-falling inertial reference masses inside the payload. The spacecrafts are maintaining an equilateral triangular constellation with 5 Million km armlength. The optical payload consists in the present configuration out of two assemblies, each one comprising a telescope, an optical bench and an inertial sensor and serving one arm of the adjacent interferometers. Due to orbital distortions, the constellation triangle is not perfectly maintained, but the line of sights offset angle is slowly changing during a one year revolution by 60°±0.75°. This variation is far beyond the diffraction limited beam width (2.5 μrad) and hence requires active compensation presently done by actuation of the complete assemblies. While allowing almost stationary on-axis operation of the optics, the arrangement requires two separate active inertial sensors, a rather sophisticated optical interfacing between the interferometer arms and active electrostatic suspension of the test masses in all but one degree of freedom.

We identified an alternative architecture, characterized by a single operational inertial sensor and a single optical bench serving both adjacent interferometer arms. Both telescopes are rigidly fixed to the optical bench and the angular breathing is accommodated by in-field of view pointing of transmit and receive beams via on-bench actuation mechanisms. Only attitude electrostatic actuation of the test mass is required, which can be kept otherwise in free fall. Such an architecture requires a decoupled inter- and intraspacecraft metrology in two steps linked via optical bench fiducial points (strap-down). Peculiar technical challenges are the actuation mechanism and the inherent metrology to calibrate or compensate within the LISA measurement band –at pm and nrad resolution- for laser phase and pointing changes, respectively, inside the optical assembly.

We present a detailed concept for the realization of the LISA optical metrology subsystem, which employs heterodyne interferometry in a so-called “strap-down” architecture to accomplish a highly sensitive detection of gravity-wave induced displacements of dedicated mass references within the payload of the three LISA satellites. A frequency swap between transmitted and local reference beam is introduced to minimize the impact of stray light on the measurement sensitivity. The performance of the system is demonstrated by first optical modeling.

The Laser Astrometric Test of Relativity (LATOR) is a Michelson-Morley-type experiment designed to test the Einstein’s general theory of relativity in the most intense gravitational environment available in the solar system – the close proximity to the Sun. By using independent time-series of highly accurate measurements of the Shapiro time-delay (laser ranging accurate to 1 cm) and interferometric astrometry (accurate to 0.1 picoradian), LATOR will measure gravitational deflection of light by the solar gravity with accuracy of 1 part in a billion, a factor ~30,000 better than currently available. LATOR will perform series of highly-accurate tests of gravitation and cosmology in its search for cosmological remnants of scalar field in the solar system. We present science, technology and mission design for the LATOR mission.

In October 2005, based on a massive response by the Science Community to ESA’s call for themes in space science, a large aperture X-ray Observatory (XRO) was identified as a candidate project for Europe within the frame of the 2015-2025 Cosmic Vision program. Such a mission would represent the natural follow-on to XMM Newton, providing a large aperture X-ray telescope combined with high spectral and time resolution instruments, capable of investigating matter under extreme conditions and the evolution of the early universe.

The paper summarises the results of the most recent ESA internal study activities, leading to an updated mission configuration, with a mirror and a detector spacecraft flying in formation around L2 and a consolidated scientific payload design. The paper also describes the ongoing technology development activities for the payload and for the spacecraft that will play a crucial role in case ESA would decide to develop such a mission.

The X-ray telescope concept for XEUS is based on an innovative high performance and light weight Silicon Pore Optics technology. The XEUS telescope is segmented into 16 radial, thermostable petals providing the rigid optical bench structure of the stand alone XRay High Precision Tandem Optics. A fully representative Form Fit Function (FFF) Model of one petal is currently under development to demonstrate the outstanding lightweight telescope capabilities with high optically effective area. Starting from the envisaged system performance the related tolerance budgets were derived. These petals are made from ceramics, i.e. CeSiC. The structural and thermal performance of the petal shall be reported. The stepwise alignment and integration procedure on petal level shall be described. The functional performance and environmental test verification plan of the Form Fit Function Model and the test set ups are described in this paper. In parallel to the running development activities the programmatic and technical issues wrt. the FM telescope MAIT with currently 1488 Tandem Optics are under investigation. Remote controlled robot supported assembly, simultaneous active alignment and verification testing and decentralised time effective integration procedures shall be illustrated.

In support of future x-ray telescopes ESA is developing new optics for the x-ray regime. To date, mass and volume have made x-ray imaging technology prohibitive to planetary remote sensing imaging missions. And although highly successful, the mirror technology used on ESA’s XMM-Newton is not sufficient for future, large, x-ray observatories, since physical limits on the mirror packing density mean that aperture size becomes prohibitive. To reduce telescope mass and volume the packing density of mirror shells must be reduced, whilst maintaining alignment and rigidity. Structures can also benefit from a modular optic arrangement. Pore optics are shown to meet these requirements. This paper will discuss two pore optic technologies under development, with examples of results from measurement campaigns on samples.

One activity has centred on the use of coated, silicon wafers, patterned with ribs, that are integrated onto a mandrel whose form has been polished to the required shape. The wafers follow the shape precisely, forming pore sizes in the sub-mm region. Individual stacks of mirrors can be manufactured without risk to, or dependency on, each other and aligned in a structure from which they can also be removed without hazard. A breadboard is currently being built to demonstrate this technology.

A second activity centres on glass pore optics. However an adaptation of micro channel plate technology to form square pores has resulted in a monolithic material that can be slumped into an optic form. Alignment and coating of two such plates produces an x-ray focusing optic. A breadboard 20cm aperture optic is currently being built.

The paper describes the optical design and performance of an extreme-ultraviolet (EUV) spectrometer for imaging spectroscopy to be part of the scientific payload of the Solar Orbiter (SOLO) mission. The main scientific objectives are to study the solar polar region and observe in detail the evolution of corona structures from a favourable point of view at only 45 solar radii from the Sun (0.2 AU).

The instrument concept is based on a grazing incidence telescope, (1200 m focal length, 18 arcmin x 18 arcmin FoV), in Wolter configuration couple to a normalincidence VLS grating spectrometer, which preserve the stigmaticity in an extended spectral region and in the whole field-of-view.

The spectral range covered by the instrument is the 116-126 nm region at the first order and the 57-63 nm region at the second order. The spectral resolving element is 65 mÅ (I order), corresponding to a velocity resolution of 16 km/s.

HAYABUSA, launched May 2003, is the first Japanese spacecraft to explore the small asteroid Itokawa. HAYABUSA had rendezvous Itokawa in three month in 2005 and touched down it twice to sample the material from it. LIDAR is a one of important navigation sensor to measure the distance between HAYABUSA and Itokawa from 50km to 50m. LIDAR operated in the three months and was estimated to have shot more than 4 million laser pulses and had supplied the ranging data to spacecraft navigation system to approach Itokawa down to 30 m.

Within ESA’s Innovation Triangle Initiative (ITI) a demonstrator breadboard for a micro-ranging-laser device “MYLRAD” has been developed. Its working principle is the measurement of the round-trip delay time of a laser beam as a phase shift. The demonstrator consists of the laser diode (30 mW, square wave AM), optics, APD detector, narrowband preamplifier, limiter, and a phase digitiser based on a novel noise-shaping synchroniser (NSS) circuit; this works without ADCs and can be built from rad-hard components for space. The system timing and the digitiser algorithm are performed by an FPGA. The demonstrator has been tested at ranges from 1 m to 30 m. With a static non-cooperative target an RMS noise of 1 mm at a result rate of 60 Hz was reached. The demonstrator needs less than 2.5 W power.

In the context of formation flying projects, one of the major points is the required precision on the intersatellites distance and/or relative displacement. According to the mission, these needs are more or less restrictive, leading to the use of fine laser metrology.

Thus, for the needs of PEGASE mission – a possible DARWIN in flight demonstration- SAGEIS-CSO has been asked by CNES to design a fine longitudinal sensor able to work at 120 K while performing displacement measurements at a working distance range of 25 to 250 m. Its required performances are a resolution and a precision of 25 nm.

This activity succeeds to the MOUSE II system development, which has demonstrated the ability to obtain the required laser metrology using a frequency stabilised laser, a compact and totally passive Michelson type sensor head plus a detection unit for data processing. Optical signals are routed using fibres, allowing the sensor head to be alone in a cryogenic environment.

Now, the goal is to obtain a validated prototype at a MQ level by the end of 2007.

For that, the laser source will be an update of the flight models made for IASI, using a more powerful DFB diode, pin-to-pin compatible with the previous design, and then giving minor changes. The current regulation was optimized in order not to degrade the narrow diode spectral width.

The opto-thermo-mechanical design of the sensor head, in collaboration with AAS, is also under progress, and constitutes the major evolution of the MOUSE II.

One of ESA’s future missions is the Darwin Space Interferometer, which aims to detect planets around nearby stars using optical aperture synthesis with free-flying telescopes. Since this involves interfering white (infra-red) light over large distances, the mission is not possible without a complex metrology system that monitors various speeds, distances and angles between the satellites. One of its sub-systems should measure absolute distances with an accuracy of around 70 micrometer over distances up to 250 meter. To enable such measurements, we are investigating a technique called frequency sweeping interferometry, in which a single laser is swept over a large known frequency range. Central to our approach is the use of a very stable, high finesse Fabry-P´erot cavity, to which the laser is stabilized at the endpoints of the frequency sweep. We will discuss the optical set-up, the control system that controls the fast sweeping, the calibration and the data analysis. We tested the system using long fibers and achieved a repeatability of 50 micrometers at a distance of 55 meters. We conclude with some recommendations for further improvements and the adaption for use in space.

In the framework of activities dedicated to the GAIA mission, Alcatel Alénia Space has developed a High Stability Optical Bench (HSOB) made with CeSiC. A key criterion was the stability of its geometry, requiring it to be confirmed by tests.

The idea was to use a metrologic system able to work in a primary vacuum environment with sub-nanometric resolution and reproducibility compliant with the expected performances of the bench.

In answer to these requirements, SAGEIS-CSO has proposed a system consisting of a frequency stabilised laser, an optical coupler, two optical sensor heads named MOUSE I and a detection unit. The delivered information is a longitudinal displacement measurement between the sensor and its joint retroreflector.

Verification of the resolution by tests has given a value of about 15 pm in a 15 Hz pass band.

Displacement repeatability versus temperature has been checked before tests campaign and in the final configuration, giving a value between ±1.4 nm/K and ±1 nm/K. These excellent performances allowed the sensor to qualify the stability of the HSOB.

COROTEL is the telescope of the COROT Satellite which aims at measuring stellar flux variations very accurately. To perform this mission, COROTEL has to be very well protected against straylight (from Sun and Earth) and must be very stable with time.

Thanks to its high experience in this field, Alcatel Alenia Space has proposed, manufactured and tested an original telescope concept associated with a high baffling performance. Since its delivery to LAM (Laboratoire d'Astrophysique de Marseille, CNRS) the telescope has passed successfully the qualification tests at instrument level performed by CNES. Now, the instrument is mounted on a Proteus platform and should be launched end of 2006. The satellite should bring to scientific community for the first time precious data coming from stars and their possible companions.

In the frame of the PLANCK mission telescope development, it is requested to measure the reflector changes of the surface figure error (SFE) with respect to the best ellipsoid, between 293 K and 50 K, with 1 μm RMS accuracy. To achieve this, Infra Red interferometry has been selected and a dedicated thermo mechanical set-up has been constructed.

In order to realise the test set-up for this reflector, a large aluminium convex mirror with radius of 19500 mm has been manufactured. The mirror has to operate in a cryogenic environment lower than 30 K, and has a contribution to the RMS WFE with less than 1 μm between room temperature and cryogenic temperature.

This paper summarises the design, manufacturing and characterisation of this mirror, showing it has fulfilled its requirements.

The Planck mission of the European Space Agency (ESA) is designed to image the anisotropies of the Cosmic Background Radiation Field over the whole sky. To achieve this aim, sophisticated reflectors are used as part of the Planck telescope receiving system. The system consists of secondary and primary reflectors which are sections of two different ellipsoids of revolution with mean diameters of 1 and 1.6 meters. Deformations of the reflectors which influence the optical parameters and the gain of receiving signals are investigated in vacuum and at very low temperatures. For this investigation, among the various high accuracy measurement techniques, photogrammetry was selected. With respect to the photogrammetric measurements, special considerations had to be taken into account in design steps, measurement arrangement and data processing to achieve very high accuracies. The determinability of additional parameters of the camera under the given network configuration, datum definition, reliability and precision issues as well as workspace limits and propagating errors from different sources are considered. We have designed an optimal photogrammetric network by heuristic simulation for the flight model of the primary and the secondary reflectors with relative precisions better than 1:1000’000 and 1:400’000 to achieve the requested accuracies. A least squares best fit ellipsoid method was developed to determine the optical parameters of the reflectors. In this paper we will report about the procedures, the network design and the results of real measurements.

The BepiColombo Spacecraft can’t tolerate to absorb a major fraction of the off-axis sunlight through larger payload apertures. Fortunately, there are solutions to design baffles such that they reflect the incoming radiation back through the front aperture rather than absorbing it. A Design Study, sponsored by ESA and performed by Contraves Space together with SAGEM Défense Securité, has analysed the potential of various solutions and assessed the options to manufacture them. The selected configuration has been analysed in detail for the optical, mechanical and thermal performance as well as the impact on mass and power dissipation. The size of the baffle was adapted to the needs of the BepiColombo Laser Altimeter (BELA) payload.

Alcatel Alenia Space and ECM have jointly developed a new ceramic material to produce lightweight, stiff, stable and cost effective structures and mirrors for space instrument the CesicÒ. Its intrinsic properties, added to ample manufacturing capabilities allow to manufacture stiff and lightweight cost effective mirrors and structure for space instruments. Different scale 1 flight representative CesicÒ optical structures have been manufactured and successfully tested under very strong dynamic environment and cryogenic condition down to 30K CesicÒ is also envisaged for large and lightweight space telescopes mirrors, a large CesicÒ 1 meter class mirror with an area mass of less than 25 Kg/m2 has been sized again launch loads and WFE performance and manufactured. CesicÒ applicability for large focal plane have been demonstrated through different scale 1 breadboards. Based on these successful results, AlcatelAleniaSpace and ECM are now in position to propose for space this technology with new innovative concepts thanks to the CesicÒ manufacturing capabilities. CesicÒ has therefore been selected for the structure and mirrors parts of a flight instrument payload and the manufacturing of the flight hardware is already underway. An high temperature high gain lightweight antenna breadboard is also under manufacturing for Bepi colombo mission. CesicÒ is therefore a good candidate for future challenging space instruments and is currently proposed for Japan and US space projects.

New Technology Silicon Carbide (NTSIC®) is a reaction sintered silicon carbide with very high bending strength. Two times higher bending strength than other SiC materials is important characteristics in an optical mirror for space application. The space optics is to endure the launch environment such as mechanical vibration and shock as well as lightweight and good thermal stability of their figure. NTSIC has no open pore. It provides good surface roughness for infrared and visible application, when its surface is polished without additional coatings. Additional advantages are in the fabrication process. The sintering temperature is significantly lower than that of a sintered silicon carbide ceramics and its sintering shrinkage is less than one percent. These advantages will provide rapid progress to fabricate large structures and will enable that one meter mirror will put practical use. The fabrication capability has developed from 250mm to about one meter in these two years, after previous report of NTSIC. It is concluded that NTSIC has potential to provide large lightweight optical mirror.

Space telescopes require large primary mirrors within a demanding thermal environment: observatories at L2 orbit provide a stable environment with a drawback of very low temperature. Besides, it is necessary to limit as far as possible the mirrors mass while withstanding launch loads and keeping image quality within a cryogenic environment.

ZERODUR is a well-known material extensively used for large telescope. Alcatel Alenia Space and Sagem/REOSC have combined their respective skills to go further in the lightweighting ratio of large mirror (36 kg/m² on 1.5 m²) through a detailed design, performance assessment and technology demonstration with breadboards.

Beyond on a large mirror detailed design supported by analysis, a ZERODUR mock-up has been manufacturing by Sagem/REOSC to demonstrate the achievability of the demanding parameters offering this high lightweighting ratio.

Through the ISO experience on mirror attachments, a detailed design of the mirror fixation has been done as well. A full size mock-up has been manufactured and successfully tested under thermal cycling and static loading.

Eventually, the ZERODUR stability behavior within this large temperature range has been verified through thermal cycling and image quality cryotest on a flat mirror breadboard.

These developments demonstrate that ZERODUR is a good candidate for large space cryogenic mirrors offering outstanding optical performances associated to matured and proven technology and manufacturing process.

An hexapod based telescope concept whose legs are deployable has been investigated in order to stow the secondary mirror during launch and to self-deploy it in orbit The main advantages of this concept are: a reduced volume for launch with high reduction of passive stability requirements, mass and inertia reduction inducing an agility gain. The positioning errors are corrected thanks to the vertical displacement of the hexapod feet and the final optical performance is reached thanks to adaptive optics. The paper presents the first steps towards the optimal design of a breadboard and the method developed to model the dynamic behaviour of such a structure with highly deformed flexible elements and validated with the results of sine vibration testing of the hexapod. The following part deals with the evaluation of its deployment and correction capabilities.

The LOBSTER telescopes are based on the optical arrangement of the lobster eye. The main difference from classical X-ray space telescopes in wide use is the very large field of view while the use of optics results in higher efficiency if compared with detectors without optics. Recent innovative technologies have enabled to design, to develop and to test first prototypes. They will provide deep sensitive survey of the sky in X-rays for the first time which is essential for both long-term monitoring of celestial high-energy sources as well as in understanding transient phenomena. The technology is now ready for applications in space.

he realization of astrophysical researches requires the development of high-sensitive centimeterband parabolic space radiotelescopes (SRT) with the large-size mirrors.

Constructively such SRT with the mirror size more than 10 m can be realized as deployable rigid structures.

Mesh-structures of such size do not provide the reflector reflecting surface accuracy which is necessary for the centimeter band observations.

Now such telescope with the 10 m diameter mirror is developed in Russia in the frame of "SPECTR - R" program.

External dimensions of the telescope is more than the size of existing thermo-vacuum chambers used to prove SRT reflecting surface accuracy parameters under the action of space environment factors. That’s why the numerical simulation turns out to be the basis required to accept the taken designs.

Such modeling should be based on experimental working of the basic constructive materials and elements of the future reflector.

In the article computational modeling of reflecting surface deviations of a centimeter-band of a large-sized deployable space reflector at a stage of his orbital functioning is considered.

The analysis of the factors that determines the deviations - both determined (temperatures fields) and not-determined (telescope manufacturing and installation faults; the deformations caused by features of composite materials behavior in space) is carried out.

The finite-element model and complex of methods are developed.

They allow to carry out computational modeling of reflecting surface deviations caused by influence of all factors and to take into account the deviations correction by space vehicle orientation system.

The results of modeling for two modes of functioning (orientation at the Sun) SRT are presented.

We review possible alternatives for the realization of the LISA laser assembly against the requirements and present a concept for a tailored master oscillator fiber power amplifier solution. An all-solid-state, all- fiber coupled approach with a Nd:YAG NPRO seed appears particularly attractive due to the possibility to combine excellent spectral properties and high output powers with superior environmental robustness.

New pump module concepts had to be developed for space borne applications, because a simple transformation of terrestrial solutions to space requirements was often not useful. A planar approach has been chosen, which prevents inherent draw-backs of stacks.

A new conduction cooled compact laser for laser induced spectroscopy on the Mars Science Laboratory (MSL) to be launched in 2009 is presented. An oscillator combined to amplifiers generates 30mJ at 1μm with a good spatial quality. Development prototype of this laser has been built and characterized. Environmental testing of this prototype is also reported.

Tesat-Spacecom is currently building a set flight models of frequency stabilized lasers for the ESA Missions AEOLUS and LTP. Lasers with low intensity noise in the kHz region and analogue tuning capabilities for frequency and output power are developed for the on board metrology of the LTP project, the precursor mission for LISA. This type of laser is internally stabilized by precise temperature control, approaching an ALLAN variance of 10^-9 for 100 sec. It can be easily locked to external frequency references with <50kHz bandwidth. The Seed laser for the AEOLUS mission (wind LIDAR) is used as the master frequency reference and is stabilized internally by a optical cavity. It shows a 3* 10^-11 Allan variance from time intervals 1 sec - 1000 sec. Furthermore it is step-tunable for calibration of the receiver instrument with a speed of GHz / sec by a digital command interface. Performance and environmental test results will be presented.

Laser frequency stabilisation is a necessity in all experiments demanding a metrological precision in the measurement of time, frequency, distance and displacement. Depending on the required performances of the laser source in term of precision, stability and timescale of said parameters a molecular or mechanical reference can be better suited to ensure the performance of the laser source. For both types of references, a brief overview of several locking techniques shall be presented. Special attention will be given to the implementation of both references and locking techniques, in a space environment. The technique of Tilt Locking on a Fabry-Perot (FP) cavity shall be discussed in detail, given its a priori excellent adaptability to a space environment (no active components and simplified optical design).

A four-wavelength low-power continuous-wave frequency laser reference system has been realised in the 935.4-nm range for water vapour differential absorption lidar (DIAL) applications. The system is built around laboratory extended-cavity and DFB diode lasers. Three lasers are directly locked to three water vapour absorption lines of different strength, whereas the wavelength of the fourth laser lies out of any absorption line (offline). On-line stabilisation is performed by wavelength modulation spectroscopy technique, while precise offline stabilisation is realised by an offset locking at 18.8 GHz. Offset frequency larger than 320 GHz has also been demonstrated at 1.55 μm, based on an all-fibre optical frequency comb. First steps towards the use of a photonic crystal fibre as ultra compact reference cell with long optical pathlength were realised. The developed techniques for direct and offset-lock laser stabilisation can also be applied to other gases and wavelengths, provided the required optical components are available for the laser wavelength considered.

For the water vapour DIAL “WALES” the wavelength regions around 935 nm, 942 nm and 944 nm have been identified as the most suitable wavelength ranges. These wavelengths can be obtained using opticalparametric-oscillators (OPOs), stimulated Raman shifters and the Ti-Sapphire laser but none of these systems could deliver all the needed parameters like beam quality, efficiency, pulse length and energy yet. Also these systems are comparably big and heavy making them less suitable for a satellite based application.

A fourth possibility to achieve these wavelength ranges is to shift the quasi-3-level laser lines (938 nm and 946 nm) of the Nd:YAG laser by replacing aluminium and yttrium by other rare earth elements. Changes of the host lattice characteristics lead to a shift of the upper and lower laser levels.

These modified crystals are summarized under the name of "Mixed Garnet" crystals. Only the Mixed Garnet lasers can be pumped directly with diode laser and use a direct approach to generate the required laser pulses without frequency conversion. Therefore no additional non-linear crystals or special pump lasers are needed and a higher electric to optical efficiency is expected as well as single frequency operation using spectral tuning elements like etalons.

In a first phase such mixed garnet crystals had been grown and characterised. The outcome was the selection of the gadolinium-scandium garnet for the most suitable laser crystal. During a second phase the complete laser system with output energy about 18 mJ in single 20 ns pulses and up to 8 mJ in free running mode with a combined pulse width of 250 μs at 942 nm have been demonstrated.

The results of the first laser operation and the achieved performance parameter are reported.

In the frame of the MTG Pre-Phase A study, feasibility of an instrument to fulfill the goals of the Lightning Imagery Mission has been investigated. Architecture is based on a set of four optical heads, each dedicated to observation of a fraction of the Earth disk and including a telescope, a narrow band filter, a detector and its proximity electronics. In particular, detector is characterized by a novel pixel architecture that provides autonomous lightning identification and readout of the flash data with a very high rate, reducing throughput at a minimum. This allows the instrument to fulfill mission objectives in terms of spatial and temporal resolution, with the lowest mass and power allocation. Details on instrument concept, design and budgets, as well as performance evaluation for different operative scenarios (day/night) are provided.

Pushbroom scan cameras with linear image sensors, commonly used for Earth observation from satellites, require high attitude stability during the image acquisition. Especially noticeable are the effects of high frequency attitude variations originating from micro shocks and vibrations, produced by momentum and reaction wheels, mechanically activated coolers, steering and deployment mechanics and other reasons. The SMARTSCAN imaging concept offers high quality imaging even with moderate satellite attitude stability on a sole opto-electronic basis without any moving parts. It uses real-time recording of the actual image motion in the focal plane of the remote sensing camera during the frame acquisition and a posteriori correction of the obtained image distortions on base of the image motion record. Exceptional real-time performances with subpixel accuracy image motion measurement are provided by an innovative high-speed onboard optoelectronic correlation processor. SMARTSCAN allows therefore using smart pushbroom cameras for hyper-spectral imagers on satellites and platforms which are not specially intended for imaging missions, e.g. micro satellites. The paper gives an overview on the system concept and main technologies used (advanced optical correlator for ultra high-speed image motion tracking), it discusses the conceptual design for a smart compact space camera and it reports on airborne test results of a functional breadboard model.

Today, both CCD and CMOS sensors can be envisaged for nearly all visible sensors and instruments designed for space needs. Indeed, detectors built with both technologies allow excellent electro-optics (EO) performances to be reached, the selection of the most adequate device being driven by their functional and technological features and limits. The first part of the paper shortly recalls how far CMOS Image Sensors (CIS) EO performances have been improved these last years. The second part reviews the advantages of CMOS technology for space applications, illustrated by examples of CIS developments performed by EADS Astrium and Supaéro/CIMI for current and short term coming space programs.

The performance stability of CCD detectors and video electronics during life time is an important issue for most of space missions. Several items are concerned, such as CCD dark signal increase, induced by space radiation environment (dose effects, proton hits, etc... ). Ground tests are performed to predict on-board behaviour and end-of-life performance. But generaly this approach cannot achieve a rigorous representation of mission conditions.

Experience feedback from in-flight measurements is therefore very useful in order to infer what really occurs and to allow comparison between actual findings and ground tests.

This paper presents the design and the preliminary performances of a CMOS linear array, resulting from collaboration between Alcatel Alenia Space and Cypress Semiconductor BVBA, which takes advantage of emerging potentialities of CMOS technologies.

The design of the sensor is presented: it includes 8000 panchromatic pixels with up to 25 rows used in TDI mode, and 4 lines of 2000 pixels for multispectral imaging. Main system requirements and detector tradeoffs are recalled, and the preliminary test results obtained with a first generation prototype are summarized and compared with predicted performances.

The PLEIADES-HR Earth observing satellites, under CNES development, combine a 0.7m resolution panchromatic channel, and a multispectral channel allowing a 2.8 m resolution, in 4 spectral bands. The 2 satellites will be placed on a sun-synchronous orbit at an altitude of 695 km. The camera operates in push broom mode, providing images across a 20 km swath. This paper focuses on the specifications, design and performance of the TDI detectors developed by e2v technologies under CNES contract for the panchromatic channel. Design drivers, derived from the mission and satellite requirements, architecture of the sensor and measurement results for key performances of the first prototypes are presented.

Optical and geometrical image qualities of Focal Planes, for "push-broom" high resolution remote sensing satellites, require the implementation of specific means and methods for the AIT sequence. Indeed the geometric performances of the focal plane mainly axial focusing and transverse registration, are duly obtained on the basis of adjustment, setting and measurement of optical and CCD components with an accuracy of a few microns. Since the end of the 1970s, EADS-SODERN has developed a series of detection units for earth observation instruments like SPOT and Helios. And EADS-SODERN is now responsible for the development of the Pleiades High Resolution Focal Plane assembly.

This paper presents the AIT sequences. We introduce all the efforts, innovative solutions and improvements made on the assembly facilities to match the technical evolutions and breakthrough of the Pleiades HR FP concept in comparison with the previous High Resolution Geometric SPOT 5 Focal Plane. The main evolution drivers are the implementation of strip filters and the realization of 400 mm continuous retinas. For Pleiades HR AIT sequence, three specific integration and measuring benches, corresponding with the different assembly stages, are used: a 3-D non-contact measurement machine for the assembly of detection module, a 3-D measurement machine for mirror integration on the main Focal Plane SiC structure, and a 3-D geometric coordinates control bench to focus detection module lines and to ensure they are well registered together.

The largest limitation of phase-shifting interferometry for optical testing is the sensitivity to the environment, both vibration and air turbulence. An interferometer using temporal phase-shifting is very sensitive to vibration because the various phase shifted frames of interferometric data are taken at different times and vibration causes the phase shifts between the data frames to be different from what is desired. Vibration effects can be reduced by taking all the phase shifted frames simultaneously and turbulence effects can be reduced by averaging many measurements. There are several techniques for simultaneously obtaining several phase-shifted interferograms and this paper will discuss two such techniques: 1) Simultaneous phase-shifting interferometry on a single detector array (PhaseCam) and 2) Micropolarizer phase-shifting array. The application of these techniques for the testing of large optical components, measurement of vibrational modes, the phasing of segmented optical components, and the measurement of deformations of large diffuse structures is described.

An integral field unit, to be used with the near-IR spectrometer instrument of the James Webb Space Telescope (JWST), is currently under development by SSTL and CfAI. Special problems in design and manufacture of the optical system are outlined, and manufacturing methods for critical optical elements are discussed. The optical system is complex, requiring a total of 95 mirrors to produce 30 output channels. Emphasis is placed on the advantages of free-form machining in aluminium. These include: resistance to launch stress, insensitivity to temperature variations from ambient to cryogenic, and the possibility of relatively complex mirror surface shapes.

The paper describes the optical design and performance budget of a novel catadioptric instrument chosen as baseline for the Stereo Channel (STC) of the imaging system SIMBIOSYS for the BepiColombo ESA mission to Mercury.

The main scientific objective is the 3D global mapping of the entire surface of Mercury with a scale factor of 50 m per pixel at periherm in four different spectral bands.

The system consists of two twin cameras looking at ±20° from nadir and sharing some components, such as the relay element in front of the detector and the detector itself. The field of view of each channel is 4° x 4° with a scale factor of 23’’/pixel. The system guarantees good optical performance with Ensquared Energy of the order of 80% in one pixel.

For the straylight suppression, an intermediate field stop is foreseen, which gives the possibility to design an efficient baffling system.

PHEBUS (Probing of Hermean Exosphere by Ultraviolet Spectroscopy) consists of an ultraviolet spectrometer for the MPO (Mercury Planetary Orbiter) of the Bepi-Colombo Mission.

The goal of this instrument is to detect emission lines of Mercury exosphere in the bandwidth from 55 to 315 nm by recording full spectra. This instrument is made of an entrance mobile baffle, which is necessary to scan vertically the Mercury atmosphere, an off-axis mirror entrance, a slit, two gratings and two detectors. A few different designs, simulated by optical software, are analysed in this paper. They provide essential results as the instrument spectral resolution. Besides a radiometric model is established to observe the spectra we would obtain on the detectors.

Scientific experiments on mineral and biological samples with Raman excitation below 300nm show a wealth of scientific information. The fluorescence, which typically decreases signal quality in the visual or near infrared wavelength regime can be avoided with deep ultraviolet excitation. This wavelength regime is therefore regarded as highly attractive for a compact high performance Raman spectrometer for in-situ planetary research. Main objective of the MIRAS II breadboard activity presented here (MIRAS: Mineral Investigation with Raman Spectroscopy) is to evaluate, design and build a compact fiber coupled deep-UV Raman system breadboard. Additionally, the Raman system is combined with an innovative scanning microscope system to allow effective auto-focusing and autonomous orientation on the sample surface for high precise positioning or high resolution Raman mapping.

Amongst the different instruments that have been preselected to be on-board the Pasteur payload on ExoMars is the Raman/ Laser Induced Breakdown Spectroscopy (LIBS) instrument. Raman spectroscopy and LIBS will be integrated into a single instrument sharing many hardware commonalities.

An international team under the lead of TNO has been gathered to produce a design concept for a combined Raman Spectrometer/ LIBS Elegant Bread-Board (EBB). The instrument is based on a specifically designed extremely compact spectrometer with high resolution over a large wavelength range, suitable for both Raman spectroscopy and LIBS measurements. Low mass, size and resources are the main drivers of the instrument’s design concept. The proposed design concept, realization and testing programme for the combined Raman/ LIBS EBB is presented as well as background information on Raman and LIBS.

Silicon pore optics have been proposed earlier as modular optical X-ray units in large Wolter-I telescopes that would match effective area and resolution requirements imposed by missions such as XEUS. Since then the optics have been developed further and the feasibility of the production of high-performance pore optics has been demonstrated. Optimisation of both the production and the assembly process allowed the generation of optics with larger areas with improved imaging performance. Silicon pore optics can now be manufactured with properties required for future X-ray telescopes. A suitable design that allows the implementation of pore optics into X-ray Optical Units in Wolter-I configuration was recently derived including an appropriate telescope mounting structure with interfaces for the individual components. The development status, the achieved performance and the requirements regarding future mirror production, optics assembly and related metrology for its characterisation are presented.

Formation flyers open new perspectives and allow to conceive giant, externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at approximately 100-150 m from the first one. ASPIICS (Association de Satellites Pour l’Imagerie et l’Interfromtrie de la Couronne Solaire) is a mission proposed to ESA in the framework of the PROBA-3 program of formation flying which is presently in phase A to exploit this technique for coronal observations. ASPIICS is composed of a single coronagraph which performs high spatial resolution imaging of the corona as well as 2-dimensional spectroscopy of several emission lines from the coronal base out to 3 R. The selected lines allow to address different coronal regions: the forbidden line of Fe XIV at 530.285 nm (coronal matter), Fe IX/X at 637.4 nm (coronal holes), HeI at 587.6 nm (cold matter). An additional broad spectral channel will image the white light corona so as to derive electron densities. The classical design of an externally occulted coronagraph is adapted to the detection of the very inner corona as close as 1.01 R and the addition of a Fabry-Perot interferometer using a so-called ”etalon”. This paper is dedicated to the description of the optical design and its critical components: the entrance optics and the FabryPerot interferometer.

The OMI instrument is an ultraviolet-visible imaging spectrograph that uses two-dimensional CCD detectors to register both the spectrum and the swath perpendicular to the flight direction with a 115° wide swath, which enables global daily ground coverage with high spatial resolution. This paper presents a number of examples of scientific results from the first two years in orbit, as well as a selection of in-flight radiometric, spectral and CCD detector performance and calibration results. The scientific results will show the OMI capability of measuring atmospheric phenomena with high spatial and temporal resolution. It will be shown that the OMI radiometric and spectral calibration are accurately understood. Radiation damage effects on the CCD detectors will be discussed in detail and it will be shown that it is possible to correct for the consequences to a large extent in order to minimise the impact on the scientific level-1 and level-2 data products.

Atmospheric monitoring missions aim at products like O₃, H₂O, NO₂, SO₂, BrO, CH₄, CO, CO₂ as well as aerosols and cloud information. Depending on the application area (Ozone Monitoring, Green House Gas Monitoring, Tropospheric Composition and Air Quality, Chemistry Climate Interaction etc.) total or tropospheric columns as well as profile information is required. The user community of these data as well as their central requirements w.r.t. the payload aspects will be described. A large range of relevant passive instrument types is available, in particular imaging spectrometer, sounder and polarisation measuring systems in the UV-VIS, SWIR and TIR spectral range. Differences between instruments for dedicated missions are highlighted and evolution of requirements is explained, also in comparison with relevant existing instrumentation partly in orbit today. Aspects of technology roadmaps for instrument implementation as well as synergetic effects of instrument combinations and according mission scopes are discussed.

MIBS is a spectrometer operating in the thermal infrared wavelength region, designed in frame of the phase A study for the ESA EarthCARE mission as part of the multispectral Imaging instrument MSI, which uses a 2D microbolometer array detector in stead of the more common MCT detectors.

Utilization of a microbolometer and using an integrated calibration system, results in a sensor with a size and mass reduction of at least an order of magnitude when compared to currently flying instruments with similar spectral resolution.

In order to demonstrate feasiblity a breadboard has been designed, which will be build and aligned in 2006 and will be ready for testing the forth quarter of 2006.

The development of the planetary exploration for landers makes it more and more necessary to have at our disposal small and light instruments. This is why we are developing in our laboratory a light imaging spectrometer with a wedge filter making the spectral splitting. This design already developed in other laboratories has the great advantage to need a limited number of optical components. However its drawback is that at a given instant the different spectral pixels don’t see the same spot in the field. We propose a new design to remedy this drawback by the adjunction of a dispersive system in the fore-optics.

Sounding measurements with high spatial resolution (better than 10 km horizontal and 1 km vertical) and repeat cycles better than an hour over the full Earth disk will enhance the ability of National Meteorological Services to initialise models of observations of temperature, moisture and winds.

To meet those needs, trade-off’s were performed during the Meteosat Third Generation (MTG) mission study (2003-2005) where preliminary instrument concepts for the Infra-Red Sounding (IRS) mission were investigated allowing at the same time to consolidate the technical requirements for the overall system study. The trade-off’s demonstrated that two types of instrument could fulfill the requirements: a Fourier Transform Spectrometer and a Dispersive Spectrometer.

This paper aims at comparing these two MTG-IRS sensor concepts by highlighting the differences in the constraints imposed on the characteristics and required performance at hardware level. In addition, technology criticalities and some other aspects are discussed qualitatively.

A new instrument concept for a Static Fourier Transform Spectrometer has been developed and characterized by CNES. This spectrometer is based on a Michelson interferometer concept, but a system of stepped mirrors generates all interference path differences simultaneously, without any moving parts. The instrument permits high spectral resolution measurements (≈0.1 cm⁻¹) adapted to the sounding and the monitoring of atmospheric gases. Moreover, its overall dimensions are compatible with a micro satellite platform.

The stepped mirrors are glued using a molecular bonding technique. An interference filter selects a waveband only a few nanometers wide. It limits the number of sampling points (and consequently the steps number) necessary to achieve the high resolution.

The instrument concept can be optimized for the detection and the monitoring of various atmospheric constituents. CNES has developed a version whose measurements are centered on the CO2 absorption lines at 1573 nm (6357 cm⁻¹). This model has a theoretical resolution of 40 pm (0.15 cm⁻¹) within a 5 nm (22.5 cm⁻¹) wide spectral window. It is aimed at the feasibility demonstration for atmospheric CO2 column measurements with a very demanding accuracy of better than 1%.

Preliminary measurements indicate that, although high quality spectra are obtained, the theoretical performances are not yet achieved. We discuss the causes for the achieved performances and describe foreseen methods for their improvements.

The concept of static Fourier transform interferometry at thermal infrared wavelengths is well suited in the case of narrow spectral bands that are looked at for targeted molecular species as CO and O3 for pollution and air quality monitoring, or H₂0 and CO₂ for weather forecast, down to the troposphere. It permits a high spectral resolution and a very good radiometric performance, with the advantage of a static interferometer, including no moving part. Along with other molecules sounded in the UV-VIS domain, as for instance in the TRAQ mission, SIFTI will provide scientists with a complete set for pollution measurements and air quality survey.

Our paper presents the principles of static Fourier transform spectrometry, the work led on the instrument performance model and our study of the SIFTI instrument. We describe the instrument, its main dimensions and characteristics, and its architecture and major subsystems. We eventually make a preliminary survey of the SIFTI performance budget items.

As a conclusion, we introduce the future CNES phase A study of this instrument that is started in 2006

This paper discusses various aspects of the on-ground and in-flight calibration of the OMI instrument.

The Optical Inter-orbit Communications Engineering Test Satellite (OICETS) was successfully launched on 23th August 2005 and thrown into a circular orbit at the altitude of 610 km. The main mission is to demonstrate the free-space inter satellite laser communications with the cooperation of the Advanced Relay and Technology Mission (ARTEMIS) geostationary satellite developed by the European Space Agency. This paper presents the overview of the OICETS and laser terminal, a history of international cooperation between Japan Aerospace Exploration Agency (JAXA) and ESA and typical results of the inter-orbit laser communication experiment carried out with ARTEMIS.

The LOLA program aims at characterising a 40.000 km optical link through the atmosphere between a high altitude aircraft and a geostationary platform. It opens a new area in the field of optical communications with moving platforms. A complete new optical terminal has been designed and manufactured for this program. The optical terminal architecture includes a specific pointing subsystem to acquire and stabilize the line of sight despite the induced vibrations from the aircraft and the moving pattern from the received laser signal. The optical configuration features a silicon carbide telescope and optical bench to ensure a high thermoelastic angular stability between receive and transmit beams. The communications subsystem includes fibered laser diodes developed in Europe and high performance avalanche photo detectors. Specific encoding patterns are used to maintain the performance of the link despite potential strong fading of the signal. A specific optical link model through the atmosphere has been developed and has been validated thanks to the optical link measurements performed between ARTEMIS and the Optical Ground Station located in the Canarian islands. This model will be used during the flight tests campaign that is to start this summer.

We proposed tests of quantum communication in space, whereby an entangled photon Source is placed onboard the ISS, and two entangled photons are transmitted via a simultaneous down link and received at two distant ground stations.

The aim of the QIPS project (financed by ESA) is to explore quantum phenomena and to demonstrate quantum communication over long distances. Based on the current state-of-the-art a first study investigating the feasibility of space based quantum communication has to establish goals for mid-term and long-term missions, but also has to test the feasibility of key issues in a long distance ground-to-ground experiment. We have therefore designed a proof-of-concept demonstration for establishing single photon links over a distance of 144 km between the Canary Islands of La Palma and Tenerife to evaluate main limitations for future space experiments. Here we report on the progress of this project and present first measurements of crucial parameters of the optical free space link.

A dedicated evaluation and qualification campaign has been performed on several optical COTS components in order to use them on ESA’s SMOS mission. The evaluation phase consisted of a set of critical tests and analyses and led to the selection of the flight lot component. After selection of the components, one lot of each component has been qualified for the SMOS mission.

The overall approach is presented together with a summary of all activities performed. The whole task has been handled in a joint effort between ESA, EADS CASA Espacio (prime contractor), Contraves Space AG (MOHA subsystem), TECNOLOGICA SA (component qualification experts) and the respective manufacturers, each party providing their specific know-how. Test results are presented and the issues discovered and lessons learned are addressed. Special emphasis is given to particular tests for which dedicated setups had to be designed due to the unavailability of standard equipment.

Future telecom satellite based on geo-stationary Earth orbit (GEO) will require advanced payloads in Kaband so as to receive, route and re-transmit hundreds of microwave channels over multiple antenna beams.

We report on the proof-of-concept demonstration of a analogue repeater making use of microwave photonic technologies for supporting broadband, transparent, and flexible cross-connectivity. It has microwave input and output sections, and features a photonic core for LO distribution, frequency down-conversion, and cross-connection of RF channels.

With benefits such as transparency to RF frequency, infinite RF isolation, mass and volume savings, such a microwave photonic cross-connect would compare favourably with microwave implementations, and based on optical MEMS switches could grow up to large port counts.

An optical backplane based on Wavelength Division Multiplexing (WDM) for onboard data and signal handling is introduced. It is a tunable transmitter fixed receiver architecture incorporating an NxN Arrayed Waveguide Grating (AWG) element for passive data routing between the nodes. In conjunction with star couplers both unicast and multicast capabilities are offered. The control plane has been implemented on a high-speed FPGA and a four-node demonstrator has been built. Bit-Error-Rate (BER) versus power incident on the receiver, employing three different AWGs, has been measured at a data rate of 10Gbps per link. A total switching time of 500ns has been achieved, leading to more than 95% efficiency with packet lengths greater than 10KBytes.

In this contribution, it is shown how the number of optical sources in WDM-based optical beamforming networks can be reduced. In optical beamforming networks based on several optical carriers and a dispersive medium a correspondence is established between each optical carrier and each antenna element. However, it is feasible to reduce the number of optical sources of the architecture if the optical carriers are reused by means of the combination of dispersive and non-dispersive time delays.

To sum up, this contribution shows how WDM optical beamforming architectures can be simplified combining dispersive and non-dispersive time delays to allow the use of photonic beamforming techniques in large antenna arrays. The number of optical sources of the beamformer, as well as its total size and cost, can be highly reduced using this technique. Experimental results validating the feasibility of the technique are provided.

MPB Communications (MPBC) is developing solutions to the monitoring requirements of spacecraft based on its fiber-laser and Fiber Bragg Grating expertise. This is cumulating in the Fiber Sensor Demonstrator for ESA’s Proba-2 that is scheduled for launch in 2007. The advantages of the MPBC approach include a central interrogation system that can be used to control a variety of different fiber-optic sensors including temperature, pressure, actuator status, and propellant leakage. This paper reviews the design and ground qualification of the FSD system in preparation for integration with Proba-2. The FSD will provide monitoring for various Proba-2 subsystems, including a hybrid propulsion system. Some of the challenges associated with using fiber-optics in space are discussed.

Europe is developing a new generation launcher, called Vega, a small launcher with a capacity to place satellites into polar and low-Earth orbits, which are used for many scientific and Earth observation missions. Its first launch is scheduled for early 2008. Dutch Space is responsible for the development, qualification and manufacturing of the Vega Interstage 1/2. This all-aluminium conically shaped section is designed as a monocoque structure. This subsystem of Vega has undergone its first qualification tests of force loading combined with an extensive programme of measurements (forces, displacements and strains), at TNO in Delft. In parallel to conventional strain gauges Fibre Optic Sensors (FOS) in the form of Fibre Bragg Grating (FBG) sensor arrays, consisting of five strain sensors and one temperature sensor, have been installed on different locations of the interstage. Direct comparisons of the results with conventional sensors during load tests up to several hundred tons are therefore possible. A self-evident benefit of FBG sensors in an array application is that each sensing FBG can have a different Bragg wavelength to reflect. Thus, Wavelength Division Multiplexing (WDM) can conveniently be used to distinguish the different sensing FBG’s at the receiving side. First test results from load measurements performed on the Qualification Model (QM) of the Vega Interstage 1/2 are presented in this paper as well as an outlook to future integration of the FBG in this field.

A fibre optic sensor design is proposed for simultaneously measuring the 3D stress (or strain) components and temperature inside thermo hardened composite materials. The sensor is based on two fibre Bragg gratings written in polarisation maintaining fibre. Based on calculations of the condition number, it will be shown that reasonable accuracies are to be expected. First tests on the bare sensors and on the sensors embedded in composite material, which confirm the expected behaviour, will be presented.

Modal wavefront filtering is mandatory in nulling interferometers dedicated to detect extrasolar planets. Several activities have been initiated by ESA for developing single-mode waveguides for the mid-infrared.

We present the development of fibres to be used for modal filtering within the European DARWIN mission and its scientific precursor GENIE: Chalcogenide fibres fit the wavelength range up to about 11 microns, while silver halide fibres can cover the full DARWIN wavelength range from 6.5 to 20 microns. A wide range of different manufacturing methods have been applied for producing step-index fibres. We also present the first results of manufacturing photonic crystal silver halide fibres.

We tested the modal wavefront filtering capability of the fibres in a Mach-Zehnder interferometer fed by a CO₂-laser. In addition we recorded the transverse output beam profile for each fibre. The results of both measurements are strong indicators for single-mode operation.

We identified the critical issues experienced in the course of this manufacturing activity. The efficient removing of cladding modes and the required length of the fibres, commonly strongly underestimated, turned out as the keys for successful demonstration of singlemode behaviour. We found dedicated and compatible materials acting as mode stripper for both fibre materials used.

We highlight the required steps for further improvement of the manufactured fibres and for a reasonable continuation of the fibre development activities for DARWIN.

The development of single mode chalcogenide glass fibers as wavefront filter for the DARWIN mission is reported. Melting procedures and different preform techniques for manufacturing core-cladding chalcogenide fibers are described. Bulk glass samples on the basis of Te-As-Se- and high Te-compositions have been characterized optically, by measurement of the absorption spectrum and the refractive index in the region 4 – 20 μm. Several chalcogenide core-cladding glass fiber configurations have been drawn and examined by microscopy. The mode propagation behaviour and numerical aperture of fiber samples have been determined by far field intensity distribution measurements, using a CO₂ laser at 10.6 μm. Single mode waveguide performance has been demonstrated for several fiber samples, coated with an absorbing Gallium layer for stripping of cladding modes.

With a view towards the application in space-borne optical instruments, we first performed a world-wide market survey of infrared fibers designed for the wavelength range of 1.5 μm to 18 μm. Fiber samples purchased and tested comprise fluoride fibers, chalcogenide fibers, a germanate fiber and a silver-halide fiber, as well as hollow fibers. While the majority of infrared fibers offered are of the multi-mode type, three of the fluoride fibers are single-mode. We report on the polarization degrading effect of a single-mode fiber and present a possible solution to achieve polarization maintainance by twisting the fiber. Secondly we report on measurements of numerical aperture, output beam profile, and attenuation of a hollow fiber. The measurements were performed at the wavelengths of λ= 3.39 μm and λ= 10.6 μm.

The ESA-Darwin mission is devoted to direct detection and spectroscopic characterization of earthlike exoplanets. Starlight rejection is achieved by nulling interferometry from space so as to make detectable the faintly emitting planet in the neighborhood.

In that context, Alcatel Alenia Space has developed a nulling breadboard for ESA in order to demonstrate in laboratory conditions the rejection of an on-axis source. This device, the Multi Aperture Imaging Interferometer (MAII) demonstrated high rejection capability at a relevant level for exoplanets, in singlepolarized and mono-chromatic conditions.

In this paper we report on the new multi-axial configuration of MAII and we summarize our late nulling results.

The European Space Agency's space-based Darwin mission aims to directly detect extrasolar Earth-like planets using nulling interferometry. However, in order to accomplish this using current optical technology, the interferometer input beams must be filtered to remove local wavefront errors. Although short lengths of single-mode fibre are ideal wavefront filters, Darwin's operating wavelength range of 4 - 20 μm presents real challenges for optical fibre technology. In addition to the fact that step-index fibres only offer acceptable coupling efficiency over about one octave of optical bandwidth, very few suitable materials are transparent within this wavelength range. Microstructured optical fibres offer two unique properties that hold great promise for this application; they can be made from a single-material and offer endlessly single-mode guidance. Here we explore the advantages of using a microstructured fibre as a broadband wavefront filter for 4 - 20 μm.

For the needs of the European Space Agency, SESO is developing in cooperation with the Institut Fresnel an Engineering Tool for the Qualification of Optical Coatings. The goal is to develop a standard methodology for testing the behaviour and stability of optical coatings during the air to vacuum transition.

The Engineering Tool is indeed designed to achieve in vacuum reflectance and transmittance measurements between 600 and 1700 nm. It is also designed to evaluate during the vacuum cycle partially the nature of the outgassing elements, using mass spectrometry.

We will present in our paper the concept of this equipment and the associated test method. The preliminary characterizations will be done in June 2006 on reflective coatings, one anti reflective coating and dichroic filters.

The use of optical fibers in low earth orbiting (LEO) satellites is a source of concern due to the radiation environment in which these satellites operate and the reliability of devices based on these fibers. Although radiation induced damage in optical fibers cannot be avoided, it can certainly be minimized by intelligent engineering. Qualifying fibers for use in space is both time consuming and expensive, and manufacturers of satellites and their payloads have started to ask for radiation performance data from optical fiber vendors. Over time, Nufern has developed fiber designs, compositions and processes to make radiation hard fibers. Radiation performance data of a variety of fibers that find application in space radiation environment are presented.

Proton irradiation was carried out on emerging semiconductor laser technologies, including Distributed Bragg Reflector (DBR) and Sampled Grating (SG)- DBR lasers at 1550 nm, as well as Distributed Feedback (DFB) lasers at 935 nm and 1550 nm. Two separate exposure sessions, at low and high doses, were performed, the first to mimic a typical 2-year Earth Observation mission, and the second for more comprehensive radiation hardness assessment. Low dose exposure yielded minimal damage to all lasers, but the 935 nm DFBs did exhibit small changes in tuning efficiency. In-situ measurements on the 1550 nm DFB and DBR lasers show degradation in lasing threshold by 15% and 4% respectively, and the DBR mode structure is maintained but shifts by more than one mode width.

In this work we present a study on teh Super Luminescent LIght Emitting Diodes (SLEDs) performance under high doses of gamma radiation. We investigate GaAs SLEDs with emission wavelengths around 830 nm. The devices were exposed to ionising radiation at a dose rate of about 4.7 Gy/s, up to a cumulated dose of 10.1 MGy in the CMF facility of the Belgian nuclear research centre SCK•CEN. We measured the device characteristics before adn after irradiation. We show that the SLED performance is only marginally affected.

Based on the micro-electronics fabrication process, Micro-Opto-Electro-Mechanical Systems (MOEMS) are under study in order to be integrated in next-generation astronomical instruments for ground-based and space telescopes. Their main advantages are their compactness, scalability, specific task customization using elementary building blocks, and remote control. At Laboratoire d’Astrophysique de Marseille, we are engaged since several years in the design, realization and characterization of programmable slit masks for multi-object spectroscopy and micro-deformable mirrors for wavefront correction. First prototypes have been developed and show results matching with the requirements.

Small-dimension, low-mass spectrometers are useful for both Earth observation and planetary missions. A very compact multi-spectral mini-spectrometer that contains no moving parts, can be constructed combining a graded-thickness filter, having a spatially variable narrow-band transmission, to a CCD array detector. The peak wavelength of the transmission filter is moving along one direction of the filter surface, such that each line of a two-dimensional array detector, equipped with this filter, will detect radiation in a different pass band. The spectrum of interest for image spectrometry of the Earth surface is very wide, 400-1000nm. This requirement along with the need of a very small dimension, makes this filter very difficult to manufacture. Preliminary results on metal-dielectric wedge filters, with a gradient of the transmission peak wavelength equal to 60nm/mm, are reported.

In the frame of the CNES Pleiades satellite, a reduction of the star tracker low frequency error, which is the most penalizing error for the satellite attitude control, was performed. For that purpose, the SED36 star tracker was developed, with a design based on the flight qualified SED16/26. In this paper, the SED36 main features will be first presented. Then, the reduction process of the low frequency error will be developed, particularly the optimization of the optical distortion calibration. The result is an attitude low frequency error of 1.1" at 3 sigma along transverse axes. The implementation of these improvements to HYDRA, the new multi-head APS star tracker developed by SODERN, will finally be presented.

The study of a Direct Visualization Display Tool (DVDT) for space applications is reported. The review of novel technologies for a compact display tool is described. Several applications for this tool have been identified with the support of ESA astronauts and are presented. A baseline design is proposed. It consists mainly of OLEDs as image source; a specially designed optical prism as relay optics; a Personal Digital Assistant (PDA), with data acquisition card, as control unit; and voice control and simplified keyboard as interfaces. Optical analysis and the final estimated performance are reported. The system is able to display information (text, pictures or/and video) with SVGA resolution directly to the astronaut using a Field of View (FOV) of 20x14.5 degrees. The image delivery system is a monocular Head Mounted Display (HMD) that weights less than 100g. The HMD optical system has an eye pupil of 7mm and an eye relief distance of 30mm.

Due to their orders-of-magnitude higher frequencies, optical frequency standards are beginning to outperform the best microwave standards with respect to their stability and accuracy and, hence, offer very promising prospects for novel space-based applications. We report on recent results for optical standards in PTB based on neutral atoms and discuss the suitability of the different approaches for space applications.

Increasingly stringent demands on atomic timekeeping, driven by applications such as global navigation satellite systems (GNSS), communications, and very-long baseline interferometry (VBLI) radio astronomy, have motivated the development of improved time and frequency standards. There are many scientific applications of such devices in space.

A laboratory prototype of a pulsed optically pumped (POP) clock based on a rubidium cell with buffer gas is described. This clock has shown very interesting physical and metrological features, such as negligible light-shift, strongly reduced cavity-pulling and very good frequency stability. In this regard, an Allan deviation of σ_y(τ) = 1.2 τ^-1/2 for measurement times up to τ = 10⁵ s has been measured. These results confirm the interesting perspectives of such a frequency standard and make it very attractive for several technological applications, such as radionavigation.

We present our development activities on compact Rubidium gas-cell atomic frequency standards, for use in space-borne and ground-based applications. We experimentally demonstrate a high-performance laser optically-pumped Rb clock for space applications such as telecommunications, science missions, and satellite navigation systems (e.g. GALILEO). Using a stabilised laser source and optimized gas cells, we reach clock stabilities as low as 1.5·10^-12 τ^-1/2 up to 10³ s and 4·10^-14 at 10⁴ s. The results demonstrate the feasibility of a laser-pumped Rb clock reaching < 1·10^-12 τ^-1/2 in a compact device (<2 liters, 2 kg, 20 W), given optimization of the implemented techniques. A second activity concerns more radically miniaturized gas-cell clocks, aiming for low power consumption and a total volume around 1 cm³ , at the expense of relaxed frequency stability. Here miniaturized “chip-scale” vapour cells and use of coherent laser interrogation techniques are at the heart of the investigations.

Narrow ro-vibrational transitions in ultracold molecules are excellent candidates for frequency references in the near-IR to visible spectral domain and interesting systems for fundamental tests of physics, in particular for a satellite test of the gravitational redshift of clocks. We have performed laser spectroscopy of several ro-vibrational overtone transitions υ = 0 → υ = 4 in HD⁺ ions at around 1.4 μm. 1+1 REMPD was used as a detection method, followed by measurement of the number of remaining molecules. The molecular ions were stored in a linear radiofrequency trap and cooled to millikelvin temperatures, by sympathetic cooling using laser-cooled Be⁺ ions simultaneously stored in the same trap.

We present a new generation of compact and rugged mid-infrared (MIR) difference-frequency coherent radiation sources referenced to fiber-based optical frequency comb synthesizers (OFCSs). By coupling the MIR radiation to high-finesse optical cavities, high-resolution and high-sensitivity spectroscopy is demonstrated for CH₄ and CO₂ around 3.3 and 4.5 μm respectively. Finally, the most effective detection schemes for space-craft trace-gas monitoring applications are singled out.

We present our the construction of an atom interferometer for inertial sensing in microgravity, as part of the I.C.E. (Interferometrie Coherente pour l’Espace) collaboration. On-board laser systems have been developed based on fibre-optic components, which are insensitive to mechanical vibrations and acoustic noise, have sub-MHz linewidth, and remain frequency stabilised for weeks at a time. A compact, transportable vacuum system has been built, and used for laser cooling and magneto-optical trapping. We will use a mixture of quantum degenerate gases, bosonic ⁸⁷Rb and fermionic ⁴⁰K, in order to find the optimal conditions for precision and sensitivity of inertial measurements. Microgravity will be realised in parabolic flights lasting up to 20s in an Airbus.

Spectra of solar radiance reflected by leaves close to the Fraunhofer bands show the net contribution of chlorophyll fluorescence emission which adds to the reflected solar spectra. In a laboratory experiment, a low stray light, high resolution, 0.85 m double monochromator was used to filter radiation living leaves still attached to the plant in correspondence of the 687 nm and 760 nm O₂ absorption bands. Reference spectra from a non fluorescent white reference were also acquired. Acquisition was performed by a Microchannel plate (MCP) intensified diode array with 512 elements. A fit of the spectral data outside the absorption lines allowed to retrieve the spectral base-line as a function of wavelength for the reference panel and the leaf. Reflectance functions were determined extending the Plascyck equation system to all the resolved lines of the oxygen absorption bands and using the base-lines for the continuum values. Fluorescence was deduced from the same equation system, using both the measured leaf and reference radiance spectra and the leaf reflectance fitting function.

The TopSat camera is a low cost remote sensing imager capable of producing 2.5 metre resolution panchromatic imagery, funded by the British National Space Centre’s Mosaic programme. The instrument was designed and assembled at the Space Science & Technology Department of the CCLRC’s Rutherford Appleton Laboratory (RAL) in the UK, and was launched on the 27th October 2005 from Plesetsk Cosmodrome in Northern Russia on a Kosmos-3M.

The camera utilises an off-axis three mirror system, which has the advantages of excellent image quality over a wide field of view, combined with a compactness that makes its overall dimensions smaller than its focal length. Keeping the costs to a minimum has been a major design driver in the development of this camera.

The camera is part of the TopSat mission, which is a collaboration between four UK organisations; QinetiQ, Surrey Satellite Technology Ltd (SSTL), RAL and Infoterra. Its objective is to demonstrate provision of rapid response high resolution imagery to fixed and mobile ground stations using a low cost minisatellite.

The paper “Development of the TopSat Camera” presented by RAL at the 5^th ICSO in 2004 described the opto-mechanical design, assembly, alignment and environmental test methods implemented. Now that the spacecraft is in orbit and successfully acquiring images, this paper presents the first results from the camera and makes an initial assessment of the camera’s in-orbit performance.

Controlling line of sight instabilities due to platform μ- vibrations is a major issue for High Orbits (HO) decametric and metric Earth Observation imaging systems. Indeed, as image quality is strongly impacted by such μ-vibrations during integration time, observation from HO requires a very high angular precision around tens of millirad over tens or even hundreds of milliseconds. This angular stability requirement is out of scope for conventional Attitude and Orbit Control System (AOCS). Two different solutions – post-accumulation and closed-loop control of the line of sight – are envisaged and discussed to deal with those μ-vibrations to make possible decametric or metric Earth Observation from High Orbits.

This paper describes the study of an interferometric instrument for the high-resolution surveillance of the Earth from geostationary orbit (GEO) performed for the EUCLID CEPA 9 RTP 9.9 “High Resolution Optical Satellite Sensor” project of the WEAO Research Cell. It is an in-depth description of a part of the activities described in. The instrument design, both optical and mechanical, is described; tradeoffs have been done for different restoration methods, based on an image generated using calculated point spread functions (PSF’s) for the complete FOV. Co-phasing concept for the optical interferometer has been defined together with the optical metrology needed. Design and simulation of the overall instrument control system was carried out.

This paper describes the internal metrology breadboard development activities performed in the frame of the EUCLID CEPA 9 RTP 9.9 “High Resolution Optical Satellite Sensor” project of the WEAO Research Cell by AAS-I and INETI. The Michelson Interferometer Testbed demonstrates the possibility of achieving a cophasing condition between two arms of the optical interferometer starting from a large initial white light Optical Path Difference (OPD) unbalance and of maintaining the fringe pattern stabilized in presence of disturbances.

The future Earth observation missions aim at delivering images with a high resolution and a large field of view.

These images have to be processed to get a very accurate localisation. In that goal, the individual lines of sight of each photosensitive element must be evaluated according to the localisation of the pixels in the focal plane.

But, with off-axis Korsch telescope (like PLEIADES), the classical model has to be adapted. This is possible by using optical ground measurements made after the integration of the instrument. The processing of these results leads to several parameters, which are function of the offsets of the focal plane and the real focal length.

All this study which has been proposed for the PLEIADES mission leads to a more elaborated model which provides the relation between the lines of sight and the location of the pixels, with a very good accuracy, close to the pixel size.

PLEIADES HR are High Resolution satellites for Earth observation. Placed at 695km they reach a 0.7m spatial resolution. To allow such performances, the detectors are working in a TDI mode (Time and Delay Integration) which consists in a continuous charge transfer from one line to the consecutive one while the image is passing on the detector.

The spatial resolution, one of the most important parameter to test, is characterized by the MTF (Modulation Transfer Function). Usually, detectors are tested in a staring mode. For a higher level of performances assessment, a dedicated bench has been set-up, allowing detectors’ MTF characterization in the TDI mode. Accuracy and reproducibility are impressive, opening the door to new perspectives in term of HR imaging systems testing.

Although the noticeable progress achieved by ground-based lidars, using lidars as an operational spaceborne instruments still poses issues to be solved. A key issue is the long-term stability of the instrument over the mission lifetime, as a whole as well as at the level of each subsystem; another important issue is related to the processes of calibration in pre-launch and operational phases. Ground truth validation is also a critical process. This paper covers some of these aspects and focus on the instrument calibration and validation with a view of ensuring accurate instrument data during the whole instrument lifetime. The proposed concept is based on a combined space-ground lidar multi-calibration experiment using five lidars. The lidar instrument will be engineered for use in two versions: for ground and, qualified, for space. The lidar will need to operate at two wavelengths (first and second Nd-YAG harmonics), with polarization capability. Five similar instruments need to be employed. A spaceborne lidar will operate together with three ground-based lidar located in the tropics, sub-tropics and midlatitudes. A fifth lidar will operate for four months each year at each ground site. Such sites will coincide with the satellite overpasses. The measurement schedule will consists of series of simultaneous ground and satellite measurements at each site satellite overpass. Additional measurements from other instruments and local sites capabilities could be added.

We have investigated the formation of UV laser induced deposits on uncoated fused silica optics under simulated space conditions in presence of outgassing materials at 30°C and 100°C. We used a frequency tripled Nd:YAG laser with 355 nm wavelength, 3 ns pulse length and 100 Hz repetition rate. Optics were exposed to fluence values in the range of 0.5 – 1.0 J/cm². As contamination samples epoxy, silicone and polyurethane containing materials were used. The depositions were monitored online and in-situ by measuring the fluorescence intensity distribution with CCD cameras, where the UV laser beam itself served as excitation source for fluorescence emission. This method allows for a very sensitive detection of the onset of deposit formation. Contaminant layers with a thickness down to 20 nm can be consistently detected. The influence of water on the formation of deposits was investigated. Time-of-flight secondary ion mass spectroscopy (ToFSIMS) was used for chemical characterization of the deposits.

In the frame of a technological development for ESA space water vapor DIAL application, we show that, by the compositional tuning technique, wavelength tuning of laser materials to match the water vapor absorption lines in the wavelength region 942-943 nm (and at about 935 nm) can be achieved. From preliminary investigations, two mixed-garnet crystal families have been identified as favorable ones, Nd:YAG_1-xYSGGx and Nd:YSAG_1-xGGG_x. In this work, two compositionally tuned Nd:mixed-garnet laser systems have been developed and tested. The first one (Nd(1%):YSAG0.91 / GGG0.09) exhibits an output wavelength peak at about 942.8-943.0 nm, the latter (Nd(0.83%):YAG0.43 / YSGG0.57) at 943.2 nm. Laser action of the two compositions has been obtained both in long pulse and in Q-switching mode.

This paper describes a high-resolution optical filter (HRF) suitable for narrow bandwidth filtering in LIDAR applications. The filter is composed of a broadband interference filter and a narrowband Fabry-Perot etalon based on the capacitance stabilised concept.

The key requirements for the HRF were a bandwidth of less than 40 pm, a tuneable range of over 6 nm and a transmission greater than 50%. These requirements combined with the need for very high out-of-band rejection (greater than 50 dB in the range 300 nm to 1200 nm) drive the design of the filter towards a combination of high transmission broadband filter and high performance tuneable, narrowband filter.

It is described a measurement instrument, used as Optical Ground Support Equipment, capable of performing the characterization of a pulsed laser beam. The instrument was developed for the functional testing of the EQM and FMs of the ALADIN laser transmitter (TXA). The performed measurements are: beam shaping, M² measurement, beam angular stability, energy and wavelength measurements, pulse duration, polarization, pulse shape and spectral characterization, optical frequency stability measurement. The measurement system can work in automatic mode performing several measurements and providing automatic report generation.

Remote gas sensing for atmospheric and environmental studies using single mode emitting semiconductor lasers, e.g. in LIDAR applications has gained wide interest in the last few years. This technique has been brought to sophisticated sensitivity levels and nowadays detection limits are in the range of a few ppb. However, up until recently only semiconductor laser diode sources with wavelengths below 2.3 μm have been available, which inherently limits the detection sensitivity due to the fact that the fundamental absorption band of many gases lies in the spectral range beyond 2.3 μm. With novel distributed feedback laser diodes at wavelengths up to 2.9 μm higher detection sensitivities as compared to currently available laser based sensors are possible.

The paper gives an overview of the development of a high-performance space structure achieving an optimum combination of mass, stiffness and stability to cope with the very stringent performance requirements of ALADIN instrument, the space-borne LIDAR built for ADM-AEOLUS ESA’s Earth Explorer Mission. Kayser-Threde has been contracted in 2003 by EADS Astrium Toulouse, ALADIN instrument Prime Contractor, for the Phase C/D of ALADIN Structure PFM. The contract with ASF comprised the detailed design, development, verification, PMP qualification, and MAIV program including ALADIN Structure qualification using a complete and fully representative STM.

The Dobson Space Telescope (DST) is a research project of the Department of Astronautics at the TUBerlin. For Development and commercialisation there is a close cooperation with the network of the Berlin Space Industry (RIBB). Major Partner is the Astro- und Feinwerktechnik Adlershof GmbH a specialist for space structures and head of the industry consortia which built the DLR BIRD micro satellite. The aim of the project is to develop a new type of deployable telescope that can overcome the mass and volume limitations of small satellites. With the DST payload micro satellites of the 100kg class will be able to carry 50cm main mirror diameter optics (→ 1m GSD). Basis of this technology is the fact that a telescope is mainly empty space between the optical elements. To fold down the telescope during launch and to undfold it after the satellite reached its orbit can save 70% of payload volume and 50% of payload mass. Since these advantages continue along the value added chain DST is of highest priority for the next generation of commercial EO micro satellites. Since 2002 the key technologies for DST have been developed in test benches in Labs of TU-Berlin and were tested on board a ESA parabolic flight campaign in 2005. The development team at TU-Berlin currently prepares the foundation of a start-up company for further development and commercialisation of DST.

New technologies are proposed for large aperture and wide Field of View (FOV) space telescopes dedicated to detection of Ultra High Energy Cosmic Rays and Neutrinos flux, through observation of fluorescence traces in atmosphere and diffused Cerenkov signals.

The presented advanced detection system is a spaceborne LEO telescope, with better performance than ground-based observatories, detecting up to 10³ - 10⁴ events/year. Different design approaches are implemented, all with very large FOV and focal surface detectors with sufficient segmentation and time resolution to allow precise reconstructions of the arrival direction. In particular, two Schmidt cameras are suggested as an appropriate solution to match most of the optical and technical requirements: large FOV, low f/#, reduction of stray light, optionally flat focal surface, already proven low-cost construction technologies. Finally, a preliminary proposal of a wideFOV retrofocus catadioptric telescope is explained.

We apply a numerical method for calculating the field distribution in the region immediately behind the input facet of a dielectric step-index single-mode slab waveguide. The input waves considered are focused plane waves and Gaussian beams of various diameters, with and without misalignment. The figures obtained show the formation of radiation modes and the development of the fundamental guided mode and thus give hints on how to design pieces of single-mode fibers that are to be used as modal filters, e.g., in astronomical interferometers with excessive nulling requirements.

For the DARWIN mission the extremely low planet signal levels require an optical instrument design with utmost efficiency to guarantee the required science performance. By shaping the transverse amplitude and phase distributions of the receive beams, the singlemode fibre coupling efficiency can be increased to almost 100%, thus allowing for a gain of more than 20% compared to conventional designs. We show that the use of "tailored freeform surfaces" for purpose of beam shaping dramatically reduces the coupling degradations, which otherwise result from mode mismatch between the Airy pattern of the image and the fibre mode, and therefore allows for achieving a performance close to the physical limitations. We present an application of tailored surfaces for building a beam shaping optics that shall enhance fibre coupling performance as core part of a space based interferometer in the future DARWIN mission and present performance predictions by wave-optical simulations. We assess the feasibility of manufacturing the corresponding tailored surfaces and describe the proof of concept demonstrator we use for experimental performance verification.

We perform a calculation of the vectorial field distribution in the focal plane of a multi-axial beam combiner and show the fundamental limitations with respect to the longitudinal component of the polarization of such a combiner for nulling interferometry.

Extreme UltraViolet instrumentation often requires the use of multilayer coated optics. Such coatings have a limited working bandwidth, and therefore are optimized to perform in correspondence of specific EUV spectral lines. Nevertheless, contemporary observations of the same target in other spectral region would strongly improve scientific knowledge. In this work we present a study on multilayers optimized to achieve high efficiency also in other spectral bands. These coatings would allow the realization of very compact instruments, such as UVCI on board of the Solar Orbiter.

LYRA is a solar radiometer part of the PROBA 2 micro satellite payload. LYRA will monitor the solar irradiance in four soft X-Ray - VUV passbands. They have been chosen for their relevance to Solar Physics, Aeronomy and SpaceWeather: 1/ Lyman Alpha channel, 2/ Herzberg continuum range, 3/ Aluminium filter channel (including He II at 30.4 nm) and 4/ Zirconium filter channel. The radiometric calibration is traceable to synchrotron source standards. The stability will be monitored by on-board calibration sources (LEDs), which allow us to distinguish between potential degradations of the detectors and filters. Additionally, a redundancy strategy maximizes the accuracy and the stability of the measurements. LYRA will benefit from wide bandgap detectors based on diamond: it will be the first space assessment of revolutionary UV detectors. Diamond sensors make the instruments radiation-hard and solar-blind (insensitive to visible light) and therefore, make dispensable visible light blocking filters. To correlate the data of this new detector technology, well known technology, such as Si detectors are also embarked. The SWAP EUV imaging telescope will operate next to LYRA on PROBA-2. Together, they will provide a high performance solar monitor for operational space weather nowcasting and research.

LYRA demonstrates technologies important for future missions such as the ESA Solar Orbiter.

The future space X-ray astronomy imaging missions require very large collecting areas at still fine angular resolution and reasonable weight. The novel space Xray optics substrates such as Silicon wafers and thin thermally formed glass enable wide applications of precise and very light weight (volume densities 2.3 to 2.5 gcm^-3) optics. The recent status of novel technologies as well as developed test samples with emphasis on precise optical surfaces based on novel materials and their space applications will be presented and discussed.

The space-based gravitational wave detector LISA (Laser Interferometer Space Antenna) requires a high performance position sensor in order to measure the translation and tilt of the free flying test mass with respect to the LISA optical bench. Here, we present a mechanically highly stable and compact setup of a heterodyne interferometer combined with differential wavefront sensing for the tilt measurement which serves as a demonstrator for an optical readout of the LISA test mass position. First results show noise levels below 1 nm/√Hz and 1 μrad/√Hz, respectively, for frequencies < 10⁻³ Hz.

Atomic clocks will be used in the future European positioning system Galileo. Among them, the optically pumped clocks provide a better alternative with comparable accuracy for a more compact system. For these systems, diode lasers emitting at 852nm are strategic components. The laser in a conventional bench for atomic clocks presents disadvantages for spatial applications. A better approach would be to realise a system based on a distributed-feedback laser (DFB). We have developed the technological foundations of such lasers operating at 852nm. These include an Al free active region, a single spatial mode ridge waveguide and a DFB structure.

The device is a separate confinement heterostructure with a GaInP large optical cavity and a single compressive strained GaInAsP quantum well. The broad area laser diodes are characterised by low internal losses (<3cm -1 ), a high internal efficiency (94%) and a low transparency current density (100A/cm²). For an AR-HR coated ridge Fabry Perot laser, we obtain a power of 230mW with M²=1.3.

An optical power of 150mW was obtained at 854nm wavelength, 20°C for AR-HR coated devices. We obtain a single spatial mode emission with M²=1.21 and a SMSR over 30dB, both at 150mW.

DFB Lasers at 852.12nm, corresponding to the D2 caesium transition, were then realised with a power of 40mW, 37°C for uncoated devices. The SMSR is over 30dB and the M²=1.33 at 40mW. Furthermore, the preliminary results of the linewidth obtained with a Fabry Perot interferometer give a value of less than 2MHz.

This paper describes a novel technique used to get a high frequency stable pulsed laser used for spaceborn applications. The Laser assembly is based on a diode pumped tripled Nd:YAG laser, used to generate tunable laser pulses of 150 mJ at a nominal wavelength of 355 nm. This laser can operates in single mode at a pulse repetition rate of 100 Hz. A high frequency stability (< 4MHzrms @355nm) of the emitted laser pulse is maintained over several tens of seconds. A long time stability of 60MHz is also provided.

Diffractive MEMS are interesting for a wide range of applications, including displays, scanners or switching elements. Their advantages are compactness, potentially high actuation speed and in the ability to deflect light at large angles.

We have designed and fabricated deformable diffractive MEMS grating to be used as tuning elements for external cavity lasers. The resulting device is compact, has wide tunability and a high operating speed.

The initial design is a planar grating where the beams are free-standing and attached to each other using leaf springs. Actuation is achieved through two electrostatic comb drives at either end of the grating. To prevent deformation of the free-standing grating, the device is 10 μm thick made from a Silicon on Insulator (SOI) wafer in a single mask process.

At 100V a periodicity tuning of 3% has been measured. The first resonant mode of the grating is measured at 13.8 kHz, allowing high speed actuation. This combination of wide tunability and high operating speed represents state of the art in the domain of tunable MEMS filters.

In order to improve diffraction efficiency and to expand the usable wavelength range, a blazed version of the deformable MEMS grating has been designed. A key issue is maintaining the mechanical properties of the original device while providing optically smooth blazed beams. Using a process based on anisotropic KOH etching, blazed gratings have been obtained and preliminary characterization is promising.

A new advanced optical system is proposed and analysed in this work with the purpose to improve the photons collection efficiency of Multi-AnodePhotoMultipliers (MAPMT) detectors, which will be used to cover large focal surface of instruments dedicated to the Ultra High Energy Cosmic Rays (UHECRs, above 10¹⁹eV) and Ultra High Energy Neutrino (UHEN) detection. The employment of the advanced optical system allows to focus all photons inside the sensitive area of detectors and to improve the signal-to-noise ratios in the wavelength range of interest (300-400nm), thus coupling imaging and filtering capability. Filter is realised with a multilayer coating to reach high transparency in UV range and with a sharp cut-off outside. In this work the applications on different series of PMTs have been studied and results of simulations are shown. First prototypes have been realised.

Finally, this paper proposes another class of adapters to be optically coupled on each pixel of MAPMT detector selected, consisting of non-imaging concentrators as Winston cones.

Optimum application of micro system technologies allows building small sensor systems that will alter procurement strategies for spacecraft manufacturers. One example is the decreased size and cost for state of the art sunsensors. Integrated sensor systems are being designed which, through use of microsystem technology, are an order of magnitutde smaller than most current sunsensors and which hold due to the large reproducibility through batch manufacturing the promise of drastic price reduction. If the Commercial Of The Shelf (COTS) approach is adopted by satellite manufacturers, this will drastically decrease mass and cost budgets associated with sunsensing applications.

Metal-dielectric light absorbers are of great interest for suppressing stray light in optical systems. Such coatings can give an absorption level greater than 99.9% over a broad spectral range provided that the complex refractive index of metallic films is accurately known. For this purpose we developed a new real-time monitoring system that allows to measure in situ both reflectance and transmittance of the coating during manufacturing in the deposition chamber. This paper describes the system design and its characteristics and gives some preliminary results concerning metallic thin film characterizations.

In our contribution we propose to use of a two-mode optical fiber as a primary source in a transmitting optical head instead of the laser diode. The distribution of the optical intensity and the complex degree of the coherence on the output aperture of the lens that is irradiated by a step-index weakly guiding optical fiber is investigated. In our treatment we take into account weakly guided modes with polarization corrections to the propagation constant and unified theory of second order coherence and polarization of electromagnetic beams.

To determine the quality of the Optical Wireless Links (OWL), there is necessary to establish the availability and the probability of interruption. This quality can be defined by the optical beam bit error rate (BER). Bit error rate BER presents the percentage of successfully transmitted bits. In practice, BER runs into the problem with the integration time (measuring time) determination. For measuring and recording of BER at OWL the bit error ratio tester (BERT) has been developed.

The 1 second integration time for the 64 kbps radio links is mentioned in the accessible literature. However, it is impossible to use this integration time for singularity of coherent beam propagation.

In the article we concentrate our attention on the quantum description of states which are prepared by light sources. The main goal of the article is the determination of density matrix of background radiation source. It is shown that these matrix elements satisfy Geometric distribution in the number state representation.

Polymeric multimode waveguides are of particular interest for optical interconnections in short-reach data links. In some applications, for example in space-borne systems, the use of advanced materials with outstanding performance in extreme environments is required (temperature and radiation). In this paper therefore, we present novel siloxane polymers suitable for these applications. The materials are used to form straight, 90° bent and spiral polymer waveguides by low-cost conventional photolithographic techniques on FR4 substrates. The samples have been tested to investigate their propagation characteristics and demonstrate their potential for high-speed data links. Overall, there is strong evidence that these multimode waveguides can be successfully employed as high-speed short-reach data links. Their excellent thermal properties, their low cost and the simple fabrication process indicate their suitability for a wide range of space applications.

Novel interrogation methods for static and dynamic measurements of mechanical deformations by fiber Bragg-gratings (FBGs) structures are presented. The sensor-reflected radiation gives information on suffered strain, with a sensitivity dependent on the interrogation setup. Different approaches have been carried out, based on laser-frequency modulation techniques and near-IR lasers, to measure strain in single-FBG and in resonant high-reflectivity FBG arrays. In particular, for the fiber resonator, the laser frequency is actively locked to the cavity resonances by the Pound-Drever-Hall technique, thus tracking any frequency change due to deformations. The loop error and correction signals fed back to the laser are used as strain monitor. Sensitivity limits vary between 200 nε/√Hz in the quasi-static domain (0.5÷2 Hz), and between 1 and 4 nε/√Hz in the 0.4-1 kHz range for the single-FBG scheme, while strain down to 50 pε can be detected by using the laser-cavity-locked method.

“Atomic Clock Ensemble in Space” (ACES) is a mission in fundamental physics that will operate a new generation of atomic clocks in the microgravity environment of the International Space Station (ISS). The ACES clock signal will combine the medium term frequency stability of a space hydrogen maser (SHM) and the long term stability and accuracy of a frequency standard based on cold cesium atoms (PHARAO). Fractional frequency stability and accuracy of few parts in 10¹⁶ will be achieved. The on-board time base distributed on Earth via a microwave link (MWL) will be used to test fundamental laws of physics (Einstein’s theories of Special and General Relativity, Standard Model Extension, string theories…) and to develop applications in time and frequency metrology, universal time scales, global positioning and navigation, geodesy and gravimetry.

After a general overview on the mission concept and its scientific objectives, the present status of ACES instruments and sub-systems will be discussed.

Observatoire de Neuchâtel (ON) is developing a compact optically-pumped cesium beam frequency standard in the frame of an ESA-ARTES 5 project. The simplest optical scheme, which is based on a single optical frequency for both preparation and detection processes of atoms, has been chosen to fulfill reliability constraints of space applications. With our laboratory demonstrator operated at 852 nm (D2 line), we have measured a frequency stability of σ_y=2.74x10^-12 τ ^-1/2, which is compliant with the Galileo requirement. The atomic resonator is fully compliant to be operated with a single diode laser at 894 nm (D₁ line). Sensitivity measurements of the clock signal to the microwave power and to the optical pumping power are also presented. Present performance limitations are discussed and further improvements are proposed in order to reach our ultimate frequency stability goal of σ_y=1x10^-12 τ ^-1/2. The clock driving software is also briefly described.