The idea of deploying a lidar system on an Earthorbiting satellite stems from the need for continuously providing profiles of our atmospheric structure with high accuracy and resolution and global coverage. Interest in this information for climatology, meteorology and the atmospheric sciences in general is huge. Areas of application range from the determination of global warming and greenhouse effects, to monitoring the transport and accumulation of pollutants in the different atmospheric regions (such as the recent fires in Southeast Asia), to the assessment of the largely unknown microphysical properties and the structural dynamics of the atmosphere itself.

Spaceborne lidar systems have been the subject of extensive investigations by the European Space Agency since mid 1970’s, resulting in mission and instrument concepts, such as ATLID, the cloud backscatter lidar payload of the EarthCARE mission, ALADIN, the Doppler wind lidar of the Atmospheric Dynamics Mission (ADM) and more recently a water vapour Differential Absorption Lidar considered for the WALES mission. These studies have shown the basic scientific and technical feasibility of spaceborne lidars, but they have also demonstrated their complexity from the instrument viewpoint. As a result, the Agency undertook technology development in order to strengthen the instrument maturity. This is the case for ATLID, which benefited from a decade of technology development and supporting studies and is now studied in the frame of the EarthCARE mission. ALADIN, a Direct Detection Doppler Wind Lidar operating in the Ultra -Violet, will be the 1^st European lidar to fly in 2007 as payload of the Earth Explorer Core Mission ADM. WALES currently studied at the level of a phase A, is based upon a lidar operating at 4 wavelengths in near infrared and aims to profile the water vapour in the lower part of the atmosphere with high accuracy and low bias. Lastly, the European Space Agency is extending the lidar instrument field for Earth Observation by initiating feasibility studies of a spaceborne concept to monitor atmospheric CO2 and other greenhouse gases.

The purpose of this paper is to present the instruments concept and related technology/instrument developments that are currently running at the European Space Agency. The paper will also outline the development planning proposed for future lidar systems.

The Atmospheric LAser Doppler INstrument (ALADIN) is the payload of the ESA’s ADMAEOLUS mission, which aims at measuring wind profiles as required by the climatology and meteorology users. ALADIN belongs to a new class of Earth Observation payloads and will be the first European Lidar in space. The instrument comprises a diode-pumped high energy Nd:YAG laser and a direct detection receiver operating on aerosol and molecular backscatter signals in parallel. In addition to the Proto- Flight Model (PFM)., two instrument models are developed: a Pre-development Model (PDM) and an Opto-Structure-Thermal Model (OSTM). The flight instrument design and the industrial team has been finalised and the major equipment are now under development. This paper describes the instrument design and performance as well as the development and verification approach. The main results obtained during the PDM programme are also reported. The ALADIN instrument is developed under prime contractorship from EADS Astrium SAS with a consortium of thirty European companies.

The atmospheric lidar ATLID is part of the payload of the joint collaborative satellite mission Earth Cloud and Aerosol Explorer (EarthCARE) conducted by the European Space Agency (ESA) and the National Space Development Agency of Japan (JAXA).

In December 2002, ESA granted Alcatel Space with a phase A study of the EarthCARE mission in which Alcatel Space is also in charge to define ATLID.

The primary objective of ATLID at the horizon 2011 is to provide global observation of clouds in synergy with a cloud profiling radar (CPR) mounted on the same platform. The planned spaceborne mission also embarks an imager and a radiometer and shall fly for 3 years.

The lidar design is based on a novel concept that maximises the scientific return and fosters a cost-effective approach. This improved capability results from a better understanding of the way optical characteristics of aerosol and clouds affect the performance budget.

For that purpose, an end to end performance model has been developed utilising a versatile data retrieval method suitable for new and more conventional approaches. A synthesis of the achievable performance will be presented to illustrate the potential of the system together with a description of the design.

The WAter vapour Lidar Experiment in Space (WALES) mission aims at providing water vapour profiles with high accuracy and vertical resolution through the troposphere and the lower stratosphere on a global scale using an instrument based on Differential Absorption Lidar (DIAL) observation technique, and mounted on an Earth orbiting satellite.

This active DIAL technique will also provide data on the cloud coverage by means of the signal reflection on the cloud layers.

In DIAL operation, backscatter lidar signals at two wavelengths - at least - are detected. One wavelength (λ ON) is highly absorbed by the species of interest, while the other (λ OFF) is backscattered with minimal absorption. This difference in absorption at the two transmitted wavelengths leads to the determination of the concentration of the species of interest.

The DIAL is therefore a dual-wavelength lidar in which the signals detected at the two wavelengths are processed to extract the absolute density of water vapour.

The Phase A study performed by ALCATEL Space and their partners under contract of the European Space Agency has led to a credible and innovative concept of instrument, based on a mission performance modelling. The challenge is to foster the scientific return while minimising the development risks and costs of instrument development, in particular the laser transmitter.

The paper describes the payload design and the implementation on a low Earth orbiting (LEO) satellite.

The CHRIS instrument was launched on ESA’s PROBA platform in October 2001, and is providing hyperspectral images of selected ground areas at 17m ground sampling distance, in the spectral range 415nm to 1050nm. Platform agility allows image sets to be taken at multiple view angles in each overpass. The design of the instrument is briefly outlined, including design of optics, structures, detection and in-flight calibration system. Lessons learnt from construction and operation of the experimental system, and possible design directions for future hyperspectral systems, are discussed.

IASI is an infrared atmospheric sounder. It will provide meteorologist and scientific community with atmospheric spectra. The IASI system includes 3 instruments that will be mounted on the Metop satellite series, a data processing software integrated in the EPS (EUMETSAT Polar System) ground segment and a technical expertise centre implemented in CNES Toulouse.

The instrument is composed of a Fourier transform spectrometer and an associated infrared imager. The optical configuration is based on a Michelson interferometer and the interferograms are processed by an on-board digital processing subsystem, which performs the inverse Fourier transforms and the radiometric calibration. The infrared imager co-registers the IASI soundings with AVHRR imager (AVHRR is another instrument on the Metop satellite). The presentation will focus on the architectures of the instrument, the description of the implemented technologies and the measured performance of the first flight model.

CNES is leading the IASI program in association with EUMETSAT. The instrument Prime is ALCATEL SPACE.

Natural and anthropogenic trace constituents play an important role for the ozone budget and climate as well as in other problems of the environment. In order to prevent the dramatic impact of any climate change, exchange processes between the stratosphere and troposphere as well as the distribution and deposition of tropospheric trace constituents are investigated.

The Limb Infrared Fourier Transform spectrometer (LIFT) will globally provide calibrated spectra of the atmosphere as a function of the tangent altitude.

LIFT field of view will be 30 km × 30 km. The resolution is 30 km in azimuth corresponding to the full field of view, and 2 km in elevation, obtained by using a matrix of 15×15 detectors. The instrument will cover the spectral domain 5.7-14.7 μm through 2 different bands respectively 13.0-9.5 μm, 9.5-5.7 μm.

With a spectral resolution of 0.1 cm^-1, LIFT is a high class Fourier Transform Spectrometer compliant with the challenging constraints of limb viewing and spaceborne implementation.

Future planetary exploration on telluric or giant planets will need a new kind of instrumentation combining imaging and spectroscopy at high spectral resolution to achieve new scientific measurements, in particular for atmospheric studies in nadir configuration.

We present here a study of a Fourier Transform heterodyne spectrometer, which can achieve these objectives, in the visible or infrared. The system is composed of a Michelson interferometer, whose mirrors have been replaced by gratings, a configuration studied in the early days of Fourier Transform spectroscopy, but only recently reused for space instrumentation, with the availability of large infrared mosaics.

A complete study of an instrument is underway, with optical and electronic tests, as well as data processing analysis. This instrument will be proposed for future planetary missions, including ESA/Bepi Colombo Mercury Planetary Orbiter or Earth orbiting platforms.

MOLI instrument -for MOtionLess Interferometer- takes advantage of the new concept of static Fourier transform spectrometer. It is a high-resolution spectrometer working over a narrow bandwidth, which is adapted to a wide range of atmospheric sounding missions and compatible with micro-satellite platform.

The core of this instrument is an echelette cube. Mirrors on the classical design are replaced by stepped mirrors -integrated into that interference cube- thus suppressing any moving part. The steps’ directions being set over a perpendicular axis, the overlap of both stepped mirrors creates a cluster of so-called “echelettes”, each one corresponding to a different optical path difference (OPD). Hence the Fourier transform of the incoming radiance is directly imaged on a CCD array in a single acquisition.

The frequency domain of the measurements is selected by an interferential filter disposed on the incoming optical path. A rotating wheel equipped with several filters allows the successive measurement of spectra around some bands of interest, i.e. O₂, CO₂ and CO absorption bands.

A new concept of a high-resolution near-IR spectrometer consisting of an echelle grating combined with an acousto-optic tunable filter (AOTF) for separation of diffraction orders, is developed for space-borne studies of planetary atmospheres. A compact design with no moving parts within the mass budget of 3-5 kg allows to reach the resolving power λ/∆λ of 20000-30000. Only a small piece of spectrum in high diffraction orders can be measured at a time, but thanks to flexibility of the AOTF electrical tuning, such pieces of spectrum can be measured randomly and rapidly within the spectral range. This development can be used for accurate measurements of important atmospheric gases, such as CO2 in terrestrial atmosphere, isotopic ratios and minor gases. A spectrometer, based on this principle, SOIR (Solar Occultation InfraRed) is being built for Venus Express (2005) ESA mission. Instruments based on this principle have high potential for the studies of the Earth, in particular for measurements of isotopes of water in the lower atmosphere, either in solar occultation profiling (tangent altitude <10 km), or observing solar glint for integral quantities of the components. Small size of hardware makes them ideal for micro-satellites, which are now agile enough to provide necessary pointing for solar occultation or glint observations. Also, the atmosphere of Mars has never been observed at local scales with such a high spectral resolution. A laboratory prototype consisting of 275-mm echelle spectrometer with Hamamatsu InGaAs 512-pixel linear array and the AOTF has demonstrated λ/∆λ≈30000 in the spectral range of 1-1.7 μm. The next set up, covering the spectral ranges of 1-1.7 μm and 2.3-4.3 μm, and the Venus Express SOIR are briefly discussed.

Current Thermal infra red ( 7..14μm) multispectral imager instruments use cryogenically cooled Mercury Cadmium Telluride (MCT or HgCdTe) detectors. This causes the instruments to be bulky, power hungry and expensive.

For systems that have medium NETD (Noise Equivalent Temperature Difference) requirements and can operate with high speed optics (<1.5), room temperature microbolometer performance has increased enough to enable people to design multispectral instruments based on this new detector technology.

Because microbolometer technology has been driven by the military need for inexpensive, reliable and small thermal imagers, microbolometer based detectors are almost exclusively available in 2D format, and performance is still increasing.

Building a spectrometer for the 7 to 12 μm wavelength region using microbolometers has been discarded until now, based on the expected NETD performance.

By optimising the throughput of the optical system, and using the latest improvements in detector performance, TNO TPD has been able to design a spectrometer that is able to provide co-registered measurements in the 7 to 12 μm wavelength region yielding acceptable NETD performance.

Apart from the usual multispectral imaging, the concept can be used for several other applications, among which imaging in both the 3 to 5 and 7 to 12 μm atmospheric windows at the same time (forest fire detection and military recognisance) or wideband flame analysis (Nox detection in industrial ovens).

The Ozone Monitoring Instrument (OMI) is an ultravioletvisible imaging spectrograph that uses two-dimensional CCD detectors to register both the spectrum and the swath perpendicular to the flight direction. This allows having a 114 degrees wide swath combined with an unprecedented small ground pixel (nominally 13 x 24 km²), which in turn enables global daily ground coverage with high spatial resolution. The OMI instrument is part of NASA’s EOSAURA satellite, which will be launched in the second half of 2004. The on-ground calibration of the instrument was performed in 2002. This paper presents and discusses results for a number of selected topics from the on-ground calibration: the radiometric calibration, the spectral calibration and spectral slit function calibration. A new method for accurately calibrating spectral slit functions, based on an echelle grating optical stimulus, is discussed. The in-flight calibration and trend monitoring approach and facilities are discussed.

One of the most significant problems for space-based spectro-radiometer systems, observing Earth from space in the solar spectral band (UV through short-wave IR), is in achievement of the required absolute radiometric accuracy. Classical methods, for example using one or more sun-illuminated diffusers as reflectance standards, do not generally provide methods for monitoring degradation of the in-flight reference after pre-flight characterisation. Ratioing methods have been proposed that provide monitoring of degradation of solar attenuators in flight, thus in principle allowing much higher confidence in absolute response calibration. Two example methods are described. It is shown that systems can be designed for relatively low size and without significant additions to the complexity of flight hardware.

Hyperspectral space imagery is an emerging technology that supports many scientific, civil, security and defence operational applications. The main advantage of this remote sensing technique is that it allows the so-called Feature Extraction: in fact the spectral signature allows the recognition of the materials composing the scene. Hyperspectral Products and their applications have been investigated in the past years by Galileo Avionica to direct the instrument characteristics design. Sample products have been identified in the civil / environment monitoring fields (such as coastal monitoring, vegetation, hot spot and urban classification) and in defense / security applications: their performances have been verified by means of airborne flight campaigns. The Hyperspectral and High Resolution Imager is a space-borne instrument that implement a pushbroom technique to get strip spectral images over the Hyperspectral VNIR and SWIR bands, with a ground sample distance at nadir of 20m in a 20 km wide ground swath, with 200 spectral channels, realizing an average spectral resolution of 10nm. The High Resolution Panchromatic Channel insists in the same swath to allow for multiresolution data fusion of hyperspectral imagery.

A new class of thermal infrared (TIR) Earth Observation (EO) data will become available with the flight of miniature TIR EO instruments in a multiple micro-satellite constellation. This data set will provide a unique service for those wishing to analyse trends or rapidly detect anomalous changes in the TIR characteristics of the Earth’s surface or atmosphere (e.g. fire detection). Following a preliminary study of potential mission applications, uncooled commercial-off-the-shelf (COTS) technology was selected to form the basis of a low-cost, compact instrument capable of complementing existing visible and near IR EO capabilities on a sub-100kg Surrey micro-satellite. The preliminary 2-3 kg instrument concept has been designed to yield a 325 m ground sample distance over a 200 km swath width from a constellation altitude of 700 km. The radiometric performance, enhanced with time-delayed integration (TDI), is expected to yield a NETD less than 0.5 K for a 300 K ground scene. Fabrication and characterization of a space-ready instrument is planned for late 2004.

This paper presents a global approach of the POLDER 2 mission: from instrument design, pre-flight and inflight calibrations till the first in-flight results. The POLDER 2 sensor has been developed by the Centre National d'Etudes Spatiales, the French space agency. It is part of the payload of the ADEOS II satellite developed by JAXA and launched in December 2002. POLDER 2 collected global data from April 2003, end of ADEOS II system check out phase, till the loss of the satellite on October 2003 due to a failure of the satellite power supply system.

The POLDER 2 sensor is designed to collect global and repetitive observations of the solar radiation reflected by the Earth-Atmosphere system for climate research. The sensor is a wide field-of-view (2400 Km swath), low resolution (6x7 Km² at nadir) multi-spectral imaging radiometer / polarimeter. The instrument concept is based on a telecentric optics, a rotating wheel carrying 15 spectral filters and polarizers, and a bidimensionnal CCD detector array. The multidisciplinary scientific objectives of POLDER 2 lead to severe radiometric and geometrical requirements, as well as a very accurate calibration of the sensor. These requirements are achieved through a stable instrument design, exhaustive pre-flight and original in-flight calibrations.

A derived model of POLDER 2 instrument will be flown on the payload of the CNES PARASOL micro satellite, the launch of which is planned end 2004. The PARASOL mission is part of the “Aqua train” i.e. the formation flying of 3 satellites following EOS-PM, so called “Aqua”.

Satrec Initiative and ATSB have been developing a medium-sized aperture camera (MAC) for an earth observation payload on a small satellite. Developed as a push-broom type high-resolution camera, the camera has one panchromatic and four multispectral channels. The panchromatic channel has 2.5m, and multispectral channels have 5m of ground sampling distances at a nominal altitude of 685km. The 300mm-aperture Cassegrain telescope contains two aspheric mirrors and two spherical correction lenses. With a philosophy of building a simple and cost-effective camera, the mirrors incorporate no light-weighting, and the linear CCDs are mounted on a single PCB with no beam splitters. MAC is the main payload of RazakSAT to be launched in 2005. RazakSAT is a 180kg satellite including MAC, designed to provide high-resolution imagery of 20km swath width on a near equatorial orbit (NEqO). The mission objective is to demonstrate the capability of a high-resolution remote sensing satellite system on a near equatorial orbit. This paper describes the overview of the MAC and RarakSAT programmes, and presents the current development status of MAC focusing on key optical aspects of Qualification Model.

Image quality specifications should aimed to fulfil high resolution mission requirements of remote sensing satellites with a minimum cost. The most important trade-off to be taken into account is between Modulation Transfer Function, radiometric noise and sampling scheme. This compromise is the main driver during design optimisation and requirement definition in order to achieve good performances and to minimise the mission cost.

For the SPOT 5 satellite, a new compromise had been chosen. The supermode principle of imagery (sampling at 2.5 meter with a pixel size of 5 meter) imp roves the resolution by a factor of four compared with the SPOT 4 satellite (10 meter resolution).

This paper presents the image quality specifications of the HRG-SPOT 5 instrument. We introduce all the efforts made on the instrument to achieve good image quality and low radiometric noise, then we compare the results with the SPOT 4 instrument’s performances to highlight the improvements achieved. Then, the in-orbit performance will be described. Finally, we will present the new goals of image quality specifications for the new Pleiades-HR satellite for earth observation (0.7 meter resolution) and the instrument concept.

As part of its contribution to Earth observation from space, ALCATEL SPACE designed, built and tested the High Resolution cameras for the European intelligence satellites HELIOS I and II. Through these programmes, ALCATEL SPACE enjoys an international reputation. Its capability and experience in High Resolution instrumentation is recognised by the most customers.

Coming after the SPOT program, it was decided to go ahead with the PLEIADES HR program. PLEIADES HR is the optical high resolution component of a larger optical and radar multi-sensors system : ORFEO, which is developed in cooperation between France and Italy for dual Civilian and Defense use. ALCATEL SPACE has been entrusted by CNES with the development of the high resolution camera of the Earth observation satellites PLEIADES HR.

The first optical satellite of the PLEIADES HR constellation will be launched in mid-2008, the second will follow in 2009. To minimize the development costs, a mini satellite approach has been selected, leading to a compact concept for the camera design.

The paper describes the design and performance budgets of this novel high resolution and large field of view optical instrument with emphasis on the technological features.

This new generation of camera represents a breakthrough in comparison with the previous SPOT cameras owing to a significant step in on-ground resolution, which approaches the capabilities of aerial photography.

Recent advances in detector technology, optical fabrication and electronics make it possible for the PLEIADES HR camera to achieve their image quality performance goals while staying within weight and size restrictions normally considered suitable only for much lower performance systems.

This camera design delivers superior performance using an innovative low power, low mass, scalable architecture, which provides a versatile approach for a variety of imaging requirements and allows for a wide number of possibilities of accommodation with a mini-satellite class platform.

Embarked on-board SPOT5, the French Earth Observation Satellite, the High Resolution Stereoscopic (HRS) camera, dedicated to simultaneous acquisition of stereo pairs with 60 km x 120 km wide swath and 10 m spatial resolution create Digital Elevation Models (DEM) with 10 m elevation accuracy. After on year inorbit, the instrument exhibits excellent performances.

Mainly built around two dioptric optics arranged with a 40° angle, which optimises the elevation performances, the HRS camera was developed in one shot, direct qualification and validation on flight model.

After a description of HRS instrument architecture, design and performances, this paper describes its development and on-ground verification results. Then, the elevation in-orbit accuracy performances and the DEM end-products are presented.

Meteosat Second Generation (MSG) is a series of 3 geo-stationary satellites developed and procured by the European Space Agency (ESA) on behalf of the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). The first satellite (MSG-1) was launched on August 29, 2002 by an Ariane 5 rocket.

SEVIRI is the main MSG payload and produces 12 channels imaging in visible and IR range. The 8 Infrared Channels in the 3.9-13.4 mm band benefit from high radiometric performances thanks to the use of detectors operating at 95K and cooled by specifically designed passive radiator. During the commissioning phase, dedicated tests have been conducted to verify the SEVIRI functionality and performances. This paper presents briefly the SEVIRI design and highlights the correlation of data obtained in-flight by EUMETSAT with the ground predictions.

A particular emphasis is put on the in-orbit evolution of the IR channel gains and on the instrument decontamination.

EADS-Astrium has recently completed the development of a 2m-resolution camera, so-called RSI (Remote Sensing Instrument), for the small-satellite ROCSAT-2, which is the second component of the long-term space program of the Republic of China. The National Space Program Office of Taïwan selected EADS-Astrium as the Prime Contractor for the development of the spacecraft, including the bus and the main instrument RSI.

The main challenges for the RSI development were:
- to introduce innovative technologies in order to meet the high performance requirements while achieving the design simplicity necessary for the mission (low mass, low power)
- to have a development approach and verification compatible with the very tight development schedule

This paper describes the instrument design together with the development and verification logic that were implemented to successfully meet these objectives.

Rosetta is one of the cornerstone missions of the European Space Agency for having a rendezvous with the comet 67P/Churyumov-Gerasimenko in 2014. The imaging instrument on board the satellite is OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System), a cooperation among several European institutes, which consists of two cameras: a Narrow (NAC) and a Wide Angle Camera (WAC).

The WAC optical design is an innovative one: it adopts an all reflecting, unvignetted and unobstructed two mirror configuration which allows to cover a 12° × 12° field of view with an F/5.6 aperture and gives a nominal contrast ratio of about 10^–4.

The flight model of this camera has been successfully integrated and tested in our laboratories, and finally has been integrated on the satellite which is now waiting to be launched in February 2004.

In this paper we are going to describe the optical characteristics of the camera, and to summarize the results so far obtained with the preliminary calibration data. The analysis of the optical performance of this model shows a good agreement between theoretical performance and experimental results.

A new conduction cooled compact laser for laser induced spectroscopy is presented. An oscillator combined to an amplifier is designed to generate 30mJ at 1≠m with a good spatial quality.

We present a method of visualization of the remote sensing data that allows a quick synthesis of heterogeneous data for its interpretation by a human operator. The method is suitable for processing pictures of one optical band as well as polyzonal and hyperspectral aero pictures. It allows using a priori knowledge for visualization. Different methods of preliminary image processing can also be easily included in the model. As a result a number of alternative visualizations of the same dataset can be obtained depending on the interpretation objectives. The method is particularly efficient at the interpretation of barely visible objects. It makes it possible to reduce the influence of particular conditions of remote probing such as lightening conditions and an optical receiver on the results of visual interpretation.

Infrared spectroscopy probes the characteristic vibrational and rotational modes of chemical bonds in molecules to provide information about both the chemical composition and the bonding configuration of a sample. The significant advantage of the Infrared spectral technique is that it can be used with minimal consumables to simultaneously detect a large variety of chemical and biochemical species with high chemical specificity. To date, relatively large Fourier Transform (FT-IR) spectrometers employing variations of the Michelson interferometer have been successfully employed in space for various IR spectroscopy applications. However, FT-IR systems are mechanically complex, bulky (> 15 kg), and require considerable processing. This paper discusses the use of advanced integrated optics and smart optical coding techniques to significantly extend the performance of miniature IR spectrometers by several orders of magnitude in sensitivity. This can provide the next generation of compact, high-performance IR spectrometers with monolithically integrated optical systems for robust optical alignment. The entire module can weigh under 3 kg to minimize the mass penalty for space applications. Miniaturized IR spectrometers are versatile and very convenient for small and micro satellite based missions. They can be dedicated to the monitoring of the CO₂ in an Earth Observation mission, to Mars exobiology exploration, as well as to vital life support in manned space system; such as the cabin air quality and the quality of the recycled water supply.

In the 2010 horizon, solar space missions such as LYOT and Solar Orbiter will allow high cadence UV observations of the Sun at spatial and spectral resolution never obtained before. To reach these goals, the two missions could take advantage of spectro-imagers. A reflective only optical solution for such an instrument is described in this paper and the first results of the mock-up being built at IAS are shown.

Star trackers are opto-electronic sensors used onboard of satellites for the autonomous inertial attitude determination. During the last years, star trackers became more and more important in the field of the attitude and orbit control system (AOCS) sensors. High performance star trackers are based up today on charge coupled device (CCD) optical camera heads.

The Jena-Optronik GmbH is active in the field of opto-electronic sensors like star trackers since the early 80-ties. Today, with the product family ASTRO5, ASTRO10 and ASTRO15, all marked segments like earth observation, scientific applications and geo-telecom are supplied to European and Overseas customers.

A new generation of star trackers can be designed based on the APS detector technical features. The measurement performance of the current CCD based star trackers can be maintained, the star tracker functionality, reliability and robustness can be increased while the unit costs are saved.

A special case of optical aperture synthesis, homothetic mapping, is the topic of this paper. It allows for a wide field of view for interferometric instruments. This paper describes a testbed constructed and tested in TNO-TPD in Delft (the Netherlands). This testbed is intended as a tool to investigate the ins and outs of homothetic mapping. The homothetic mapping approach is explained, the whole setup is specified and results are shown.

The Atacama Large Millimeter Array (ALMA) project requires the development of reliable quasi-optical systems with requirements similar to the ones in space. The operating condition for optical elements of higher frequency channels are similar to the conditions in spacecraft, since these elements are contained within the ALMA cryostat in high vacuum and at cryogenic temperatures. The remote terrain of the Atacama Desert and the scale of project suggest that a significant effort should be made to ensure high reliability of the system. Therefore the techniques, common to a space mission are applied with this development.

In this report we would like to present the design of the quasi-optical system for ALMA band 9 (600-702 GHz) containing elements typical to a space system. A design assumptions and details will be presented for a frequency independent system. A measurement of near field antenna beam pattern (phase and amplitude) will be presented and comparison with theoretical predictions will be made.

In this proceeding we present a set of studies which are in progress in different labs and industrials. The aim of this project is to study the possibilities to design a very compact and reliable laser cooling bench for space and inboard applications.

A patent-pending, low-cost, moderate performance, Earth Attitude Sensor for LEO satellites is described in this paper. The paper deals with the system concepts, the technology adopted and the simulation results. The sensor comprises three or four narrow field of view mini telescopes pointed towards the Earth edge to detect and measure the variation of the off-nadir angle of the Earth-to-black sky transition using thermopile detectors suitably placed in the foci of the optical min telescopes. The system’s innovation consists in the opto-mechanical configuration adopted that is sturdy and has no moving parts being , thus, inherently reliable. In addition, with a view to reducing production costs, the sensor does without hi-rel and is instead mainly based on COTS parts suitably chosen. Besides it is flexible and can be adapted to perform attitude measurement onboard spacecraft flying in orbits other than LEO with a minimum of modifications to the basic design. At present the sensor is under development by IMT and OptoService.

A comparative accuracy analysis is performed for two types of scanning IR Earth horizon sensors developed during a few last years. Resulting measurement error contribution of certain error sources, including instability of hardware parameters, as well as influence of seasons latitude variations of the Earth IR radiance, is estimated based on computer simulation. The conclusion is motivated concerning application of the obtained results for reducing measurement errors of some IR Earth horizon sensors currently exploiting on board of the satellites.

The COROT mission is part of the program "mini-satellite" of CNES (French space agency). It implies international cooperation between European institutes and research centres. COROT aims to perform astroseismology observations and to detect exoplanets. Long duration observations of stars will be used to detect periodic variations with an afocal telescope followed by a dioptric objective and 4 CCDs. These very small variations can be caused by star seismic activities (about 10^-6 variation of signal) or transits of planets (few 10^-4 variation of signal).

Due to the orbit of the spacecraft (low altitude polar orbit) and even if the observations are performed in a direction perpendicular to orbit plane, the measurements can be disturbed by the straylight reflected by the earth (albedo) that can generate a periodic perturbation.

The paper details the overall optical design of the baffle. The baffle modelling and straylight computation methods are described and the expected performances are discussed.

This paper deals with design and prototype development of an Active Pixel Sensor — based miniature sun sensor and a laboratory facility for its indoor test and calibration. The miniature sun sensor is described and the laboratory test facility is presented in detail. The major focus of the paper is on tests and calibration of the sensor. Two different calibration functions have been adopted. They are based, respectively, on a geometrical model, which has required least-squares optimisation of system physical parameters estimates, and on neural networks. Calibration results are presented for the above solutions, showing that accuracy in the order of 0.01° has been achieved. Neural calibration functions have attained better performance thanks to their intrinsic auto-adaptive structure.

Space interferometers consisting of several free flying telescopes, such as the planned Darwin mission, require a complex metrology system to make all the components operate as a single instrument. This metrology system consists of various sub-systems to monitor distances, angles and speeds. Our research focuses on one of these sub-systems that measures the absolute distance between two satellites with high accuracy. For Darwin the required accuracy would be in the order of 10 μm over 250 meter.

To measure this absolute distance, we are currently building a frequency sweeping interferometer. It is operated by first measuring a phase in the interferometer, sweeping a tunable laser over a known frequency interval and finally measuring a second phase. By also counting the number of fringes during the sweep it is possible to determine the absolute path length difference without ambiguities. We plan on actively stabilizing the wavelength at the endpoints of the sweep on a Fabry-Perot cavity using the Pound-Drever-Hall technique. In this way the unknown distance is directly referenced to the length of the Fabry-Perot cavity.

We have demonstrated the feasibility of a free-space ultra-stable optical link on a 3 meters test bench, operating at 100 MHz. With this type of link, it is possible to transfer a 100 MHz signal with a relative frequency stability of a few 10⁻¹⁴ at one second integration time, 10⁻¹⁶ at one day and a phase stability of a few picoseconds per day in presence of moderate mechanical vibrations and thermal fluctuations.

The comparisons of modern clocks of distant (<100 km) Time and Frequency laboratories have a strong scientific interest. In this context we study a low noise frequency distribution via optical fibres. Some preliminary tests have been realized and the results are encouraging. We expect to transfer ultra stable oscillators with a relative frequency stability of a few 10⁻¹⁴ at one second integration time, 10⁻¹⁶ at one day.

Projects such as the Space Interferometry Mission (SIM) [1] and Terrestrial Planet Finder (TPF) [2] rely heavily on sub-nanometer accuracy metrology systems to define their optical paths and geometries. The James Web Space Telescope (JWST) is using this metrology in a cryogenic dilatometer for characterizing material properties (thermal expansion, creep) of optical materials. For all these projects, a key issue has been the reliability and stability of the electronics that convert displacement metrology signals into real-time distance determinations. A particular concern is the behavior of the electronics in situations where laser heterodyne signals are weak or noisy and subject to abrupt Doppler shifts due to vibrations or the slewing of motorized optics. A second concern is the long-term (hours to days) stability of the distance measurements under conditions of drifting laser power and ambient temperature.

This paper describes heterodyne displacement metrology gauge signal processing methods that achieve satisfactory robustness against low signal strength and spurious signals, and good long-term stability. We have a proven displacement-measuring approach that is useful not only to space-optical projects at JPL, but also to the wider field of distance measurements.

Parallel optical interconnects are experimentally assessed as a technology that may offer the high-throughput data communication capabilities required to the next-generation on-board digital processing units. An optical backplane interconnect was breadboarded, on the basis of a digital transparent processor that provides flexible connectivity and variable bandwidth in telecom missions with multi-beam antenna coverage. The unit selected for the demonstration required that more than tens of Gbit/s be supported by the backplane. The demonstration made use of commercial parallel optical link modules at 850 nm wavelength, with 12 channels running at up to 2.5 Gbit/s. A flexible optical fibre circuit was developed so as to route board-to-board connections. It was plugged to the optical transmitter and receiver modules through 12-fibre MPO connectors. BER below 10^-14 and optical link budgets in excess of 12 dB were measured, which would enable to integrate broadcasting. Integration of the optical backplane interconnect was successfully demonstrated by validating the overall digital processor functionality.

The distribution of high spectral purity reference signals over optical fibre in future telecommunication satellite payloads is presented. Several types of applications are considered, including the distribution of a reference frequency at 10 MHz (Ultra-Stable Reference Oscillator) as well as the distribution of a radiofrequency oscillator around 800 MHz (Master Local Oscillator). The results of both experimental and theoretical studies are reported. In order to meet phase noise requirements for the USRO distribution, the use of an optimised receiver circuit based on an optically synchronised oscillator is investigated. Finally, the optical distribution of microwave local oscillators at frequencies exceeding 20 GHz is described. Such a scheme paves the way to more advanced sub-systems involving optical frequency-mixing and optical transmission of microwave signals, with applications to multiple-beam active antennas.

The paper describes the quantum effects to be considered in the model of new integrated optical angular velocity sensors. Integrated optics provides a promising approach to low-cost, light weight, and high performance devices. Some preliminary results are also reported.

This paper describes the design and performance of the TESAT Reference Laser Head, acting as the frequency reference for the ALADIN Transmit Assembly (TXA) for the ESA AEOLUS satellite. First measurements of short time frequency stability (130 kHz rms over 360 sec) and digitally controlled coarse and fine step tuning functionality will be presented.

This paper describes the laser transmitter assembly used in the ALADIN instrument currently in C/D development phase for the ESA ADM-AEOLUS mission (EADS Astrium as prime contractor for the satellite and the instrument).

The Laser Transmitter Assembly (TXA), based on a diode pumped tripled Nd:YAG laser, is used to generate tunable laser pulses of 150 mJ at a nominal wavelength of 355 nm. This laser is operated in burst mode, with a pulse repetition cycle of 100 Hz.

The TXA is composed of the following units: a diodepumped CW Nd:YAG Laser named Reference Laser Head (RLH), used to inject a diode-pumped, Q-switched, amplified and frequency tripled Nd:YAG Laser working in the third harmonic referred as Power Laser Head (PLH) and a Transmitter Laser Electronics (TLE) containing all the control and power electronics needed for PLH and RLH operation.

The TXA is made by an European consortium under the leadership of Galileo Avionica (It), and including CESI (It), Quantel (Fr), TESAT (Ge) and Thales (Fr).

We present our ongoing development of a compact (<1.5 liters) and high-performance (10^-14 at 10⁴ s) laser-pumped Rubidium clock for space applications like, e.g., satellite navigation systems (GALILEO). A compact laser head was developed that includes frequency stabilization of the pump light to a reference cell. Recent clock stability results obtained with this laser head reach 2⋅10^-13 at 1000s, limited mainly by residual cell temperature coefficients and light shift effects. We discuss strategies to overcome these limitations and the relationship between the stabilities of the pump laser and the clock. Comparisons of the laser and clock frequency stabilities are presented for stabilization to both Doppler and sub-Doppler spectroscopy.

The PHARAO project purpose is to open the way for a new atomic clock generation in space, where laser cooling techniques and microgravity allow high frequency stability and accuracy.

The French space agency, CNES is funding and managing the clock construction. The French SYRTE and LKB laboratories are scientific and technical advisers for the clock requirements and the follow-up of subsystem development in industrial companies.

EADS SODERN is developing two main subsystems of the PHARAO clock: the Laser Source and the Cesium Tube where atoms are cooled, launched, selected and detected by laser beams. The Laser Source includes an optical bench and electronic devices to generate the laser beams required.

This paper describes PHARAO and the role laser beams play in its principle of operation. Then we present the Laser Source design, the technologies involved, and the status of development. Lastly, we focus of a key equipment to reach the performances expected, which is the Extended Cavity Laser Diode.

Cladding-pumped rare-earth-doped fiber laser technologies are currently among the best sources for high power applications. Theses extremely compact and robust sources appoint them as good candidate for aeronautical and space applications.

The double-clad (DC) fiber converts the poor beamquality of high-power large-area pump diodes from the 1^st cladding to laser light at another wavelength guided in an active single-mode core. High-power coherent MOPA (Master Oscillator Power Amplifier) sources (several 10W CW or several 100W in pulsed regime) will soon be achieved. Unfortunately it also brings nonlinear effects which quickly impairs output signal distortions. Stimulated Brillouin scattering (SBS) and optical parametric amplification (OPA) have been shown to be strong limitations.

Based on amplifier modeling and experiments we discuss the performances of these sources.

There are more or less well established technologies such as the optical-parametric-oscillator (OPO), the Raman-laser, and the Ti-Sapphire laser, which are able to emit laser light in the region of the water vapour absorption lines. For WALES the regions of about 935 nm, 942 nm, and 944 nm have been identified as the most suitable wavelength ranges. However, each of these laser designs is highly sophisticated. Current baseline for WALES is the Ti-Sapphire laser.

A fourth possibility to achieve these wavelength ranges is to shift the groundstate 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 are needed and a higher electric to optical efficiency is expected as well as single frequency operation using spectral tuning elements like etalons. Such lasers have the great potential to fulfil the requirements and to become the preferred transmitter concept for WALES as well as for follow up missions. Within a ESA study several crystal compositions have been grown, spectrally characterised and analysed.

Absorbed space radiation energy in the crystal lattice causes colour centres, which can reabsorb the pump and laser wavelength and consequently reduce the laser gain considerably. Co-dopants such as Chromium and Cerium are able to suppress the colour centres and are candidates for effective radiation hardening.

The results of the crystal tuning, the co-doping with different radiation hardeners and the radiation tests will be presented. There applicability for a space based water vapour DIAL transmitter will be discussed.

We present first, promising experiments with a novel, compact and simple Nd:YVO₄ slab laser with 12 W of 1.06 μm optical output power and a beam quality factor M² ∼ 2.5. The laser is made of a diffusion-bonded YVO₄/Nd:YVO₄ composite crystal that exhibits two unique features. First, it ensures a one-dimensional heat removal from the laser crystal, which leads to a temperature profile without detrimental influence on the laser beam. Thus, the induced thermo-optical aberrations to the laser field are low, allowing power scaling with good beam quality. Second, the composite crystal itself acts as a waveguide for the 809 nm pump-light that is supplied from a diode laser bar. Pump-light shaping optics, e.g. fast- or slow-axis collimators can be omitted, reducing the complexity of the system. Pump-light redundancy can be easily achieved. Eventually, the investigated slab laser might be suitable for distortion-free high gain amplification of weak optical signals.

We report on the progress in innovative X-ray mirror development with focus on requirements of future X-ray astronomy space projects. Various future projects in X-ray astronomy and astrophysics will require large lightweight but highly accurate segments with multiple thin shells or foils. The large Wolter 1 grazing incidence multiple mirror arrays, the Kirkpatrick-Baez modules, as well as the large Lobster-Eye X-ray telescope modules in Schmidt arrangement may serve as examples. All these space projects will require high quality and light segmented shells (shaped, bent or flat foils) with high X-ray reflectivity and excellent mechanical stability.

We are developing high-strength reaction-sintered silicon carbide (RS-SiC) mirror as one of the new promising candidates for large-diameter space-borne optics.

In order to observe earth surface or atmosphere with high spatial resolution from geostationary orbit, larger diameter primary mirrors of 1-2 m are required. One of the difficult problems to be solved to realize such optical system is to obtain as flat mirror surface as possible that ensures imaging performance in infrared - visible - ultraviolet wavelength region. This means that homogeneous nano-order surface flatness/roughness is required for the mirror.

The high-strength RS-SiC developed and manufactured by TOSHIBA is one of the most excellent and feasible candidates for such purpose. Small RS-SiC plane sample mirrors have been manufactured and basic physical parameters and optical performances of them have been measured. We show the current state of the art of the RS-SiC mirror and the feasibility of a large-diameter RS-SiC mirror for space-borne optics.

Newly developed high-strength reaction-sintered silicon carbide is an attractive material for lightweight optical mirror with two times higher bending strength than other SiC materials. The polished surface has no pore and is suited to visible region as well as infrared without CVD SiC coating. The fabrication process, with low temperature and small shrinkage, is also suited to develop large scale objects.

Optical and structural elements made of silicon carbide are increasingly found in space instruments. Chemical vapor deposited silicon carbide (CVD-SiC) is used as a reflective coating on SiC optics in reason of its good behavior under polishing. The advantage of applying ion beam figuring (IBF) to CVD-SiC over other surface figure-improving techniques is discussed herein. The results of an IBF sequence performed at the Centre Spatial de Liège on a 100 mm CVD-SiC mirror are reported. The process allowed to reduce the mirror surface errors from 243 nm to 13 nm rms . Beside the surface figure, roughness is another critical feature to consider in order to preserve the optical quality of CVD-SiC . Thus, experiments focusing on the evolution of roughness were performed in various ion beam etching conditions. The roughness of samples etched at different depths down to 3 ≠m was determined with an optical profilometer. These measurements emphasize the importance of selecting the right combination of gas and beam energy to keep roughness at a low level. Kaufman-type ion sources are generally used to perform IBF but the performance of an end-Hall ion source in figuring CVD-SiC mirrors was also evaluated in this study. In order to do so, ion beam etching profiles obtained with the end-Hall source on CVD-SiC were measured and used as a basis for IBF simulations.

Light-weight mirrors are developed for two Japanese infrared astronomical missions, ASTRO-F and SPICA. ASTRO-F is scheduled for launch in 2005, while the target year for launch of SPICA is 2010. The mirrors of the ASTRO-F telescope are made of a sandwich-type silicon carbide (SiC) material, comprising porous core and CVD coat of SiC on the surface. Cryogenic measurements of the ASTRO-F primary mirror and telescope assembly were performed extensively. As for the SPICA telescope, which has an aperture of 3.5-m diameter, carbon-fiber-reinforced SiC (C/SiC composite), as well as SiC, is one of the promising candidates for mirror material. C/SiC composite spherical test mirrors of 160-mm diameter has recently been manufactured and tested. This paper presents the experimental results of the cryogenic performance obtained for the sandwich-type SiC mirrors and the C/SiC composite mirrors.

Silicon carbide (SiC) is the most advantageous as the material of various telescope mirrors, because SiC has high stiffness, high thermal conductivity, low thermal expansion and low density and so on [1] [2]. However, since SiC is very hard, it is difficult to obtain the surfaces efficiently by using ordinary grinding method. Therefore, we developed the ultra lightweight mirror by ELID (ELectrolytic In-process Dressing) grinding method and ultra-precision grinding machine.

ELID grinding method is the new grinding technology which one of authors invented, produces the quality of the high surface efficiently, and is effective in processing of a very hard material, such as crystalline silicon and sapphire, ceramics, glasses, hard metals and so on. SiC mirror for space telescope is designed as regular polygon rib structures in the rear face for reducing weight, and both the optical face and the backside ribs are so thin that deformation of the mirror cannot disregard. Therefore, in order to feed back deformation of the mirror to the orbit of grinding wheel, it is necessary to analyze deformation.

In this research, we present the results which fabricated mirrors of sintered SiC by the ELID grinding method, the numerical calculation results of the profile deformations analyzed by FEM, and new jig for Φ360mm a mirror.

Piezoelectric actuators find their first applications in active space optics. The purpose of this paper is to describe the state of the art and some applications.

Piezo actuators display attractive features for space applications, such as precise positioning, unlubricated, non magnetic and compact features, and low power consumption. However, piezo mechanisms cannot be considered separately from their driving and control electronic. Piezo actuators, such as Amplified Piezo Actuators or Parallel Pre-stressed Actuators, initially designed under CNES contracts, shall find their first space flight applications in optics on the PHARAO Laser bench:

• fine pointing of the laser beams,

• laser cavity tuning.

Breadboard mechanisms based on piezo actuators have also been tested for refocusing purposes.

Other applications includes the improvement of the CCD resolution through an oversampling technique, such as in the SOHO/LASCO instrument, fast optical shutter operation, optical filter in combination with a Fabry - Perot interferometer, such as in future LIDAR for earth observation. The first applications shall be described and an overview of the future potential applications shall be given.

Large reflectors and antennas for the IR to mm wavelength range are being planned for many Earth observation and astronomical space missions and for commercial communication satellites as well. Scientific observatories require large telescopes with precisely shaped reflectors for collecting the electro-magnetic radiation from faint sources. The challenging tasks of on-ground testing are to achieve the required accuracy in the measurement of the reflector shapes and antenna structures and to verify their performance under simulated space conditions (vacuum, low temperatures). Due to the specific surface characteristics of reflectors operating in these spectral regions, standard optical metrology methods employed in the visible spectrum do not provide useful measurement results.

The current state-of-the-art commercial metrology systems are not able to measure these types of reflectors because they have to face the measurement of shape and waviness over relatively large areas with a large deformation dynamic range and encompassing a wide range of spatial frequencies. 3-D metrology (tactile coordinate measurement) machines are generally used during the manufacturing process. Unfortunately, these instruments cannot be used in the operational environmental conditions of the reflector.

The application of standard visible wavelength interferometric methods is very limited or impossible due to the large relative surface roughnesses involved. A small number of infrared interferometers have been commercially developed over the last 10 years but their applications have also been limited due to poor dynamic range and the restricted spatial resolution of their detectors. These restrictions affect also the surface error slopes that can be captured and makes their application to surfaces manufactured using CRFP honeycomb technologies rather difficult or impossible.

It has therefore been considered essential, from the viewpoint of supporting future ESA exploration missions, to develop and realise suitable verification tools based on infrared interferometry and other optical techniques for testing large reflector structures, telescope configurations and their performances under simulated space conditions.

Two methods and techniques are developed at CSL.

The first one is an IR-phase shifting interferometer with high spatial resolution. This interferometer shall be used specifically for the verification of high precision IR, FIR and sub-mm reflector surfaces and telescopes under both ambient and thermal vacuum conditions.

The second one presented hereafter is a holographic method for relative shape measurement. The holographic solution proposed makes use of a home built vacuum compatible holographic camera that allows displacement measurements from typically 20 nanometres to 25 microns in one shot. An iterative process allows the measurement of a total of up to several mm of deformation. Uniquely the system is designed to measure both specular and diffuse surfaces.

This article deals with instrumentation challenges of the stellar interferometry mission IRSI-Darwin of the European Space Agency. The necessity to have a reliable and performant system for beam recombination has enlightened the advantages of an integrated optics solution, which is already in use for ground-base interferomety in the near infrared. However, since Darwin will operate in the mid infrared, this requires extending the integrated optics concept in this spectral range. This paper presents the guiding lines of the characterization work that should validate a new integrated optics concept for the mid infrared. We present also one example of characterization experiment we are working on.

The grism is a versatile dispersion element for an astronomical instrument ranging from ultraviolet to infrared. Major benefit of using a grism in a space application, instead of a reflection grating, is the size reduction of optical system because collimator and following optical elements could locate near by the grism. The surface relief (SR) grism is consisted a transmission grating and a prism, vertex angle of which is adjusted to redirect the diffracted beam straight along the direct vision direction at a specific order and wavelength. The volume phase holographic (VPH) grism consists a thick VPH grating sandwiched between two prisms, as specific order and wavelength is aligned the direct vision direction. The VPH grating inheres ideal diffraction efficiency on a higher dispersion application. On the other hand, the SR grating could achieve high diffraction efficiency on a lower dispersion application. Five grisms among eleven for the Faint Object Camera And Spectrograph (FOCAS) of the 8.2m Subaru Telescope with the resolving power from 250 to 3,000 are SR grisms fabricated by a replication method. Six additional grisms of FOCAS with the resolving power from 3,000 to 7,000 are VPH grisms. We propose “Quasi-Bragg grism” for a high dispersion spectroscopy with wide wavelength range.

The germanium immersion grating for instance could reduce 1/64 as the total volume of a spectrograph with a conventional reflection grating since refractive index of germanium is over 4.0 from 1.6 to 20 μm. The prototype immersion gratings for the mid-InfraRed High dispersion Spectrograph (IRHS) are successfully fabricated by a nano-precision machine and grinding cup of cast iron with electrolytic dressing method.

IASI (Infrared Atmospheric Sounding Interferometer) is an infrared atmospheric sounder. It will provide meteorologist and scientific community with atmospheric spectra. The instrument is composed of a Fourier transform spectrometer and an associated infrared imager.

The presentation will describe the spectrometer detection chain architecture, composed by three different detectors cooled in a passive cryo-cooler (so called CBS : Cold Box Subsystem) and associated analog electronics up to digital conversion. It will mainly focus on design choices with regards to environment constraints, implemented technologies, and associated performances.

CNES is leading the IASI program in collaboration with EUMETSAT. The instrument Prime is ALCATEL SPACE responsible, notably, of the detection chain architecture. SAGEM SA provides the detector package (so called CAU : Cold Acquisition Unit).

Imaging detectors are key elements for optical instruments and sensors on board space missions dedicated to Earth observation (high resolution imaging, atmosphere spectroscopy...), Solar System exploration (micro cameras, guidance for autonomous vehicle...) and Universe observation (space telescope focal planes, guiding sensors...). This market has been dominated by CCD technology for long. Since the mid- 90s, CMOS Image Sensors (CIS) have been competing with CCDs for more and more consumer domains (webcams, cell phones, digital cameras...). Featuring significant advantages over CCD sensors for space applications (lower power consumption, smaller system size, better radiations behaviour...), CMOS technology is also expanding in this field, justifying specific R&D and development programs funded by national and European space agencies (mainly CNES, DGA, and ESA). All along the 90s and thanks to their increasingly improving performances, CIS have started to be successfully used for more and more demanding applications, from vision and control functions requiring low-level performances to guidance applications requiring medium-level performances. Recent technology improvements have made possible the manufacturing of research-grade CIS that are able to compete with CCDs in the high-performances arena. After an introduction outlining the growing interest of optical instruments designers for CMOS image sensors, this talk will present the existing and foreseen ways to reach high-level electro-optics performances for CIS. The developments of CIS prototypes built using an imaging CMOS process and of devices based on improved designs will be presented.

In the framework of the Pléiades program, Alcatel Space is developping with CNES a new concept of Highly Integrated Detection Electronic Subsystem (SEDHI) which lead to very high gains in term of camera mass, volume and power consumption. This paper presents the design of this new concept and summarizes its main performances.

The electrical, mechanical and thermal aspects of the SEDHI concept are described, including the basic technologies: panchromatic detector, multispectral detector, butting technology, ASIC for phase shift of detector clocks, ASIC for video processing, ASIC for phase trimming, hybrids, video modules... This concept and these technologies can be adapted to a large scale of missions and instruments. Design, performance and budgets of the subsystem are given for the Pléiades mission for which the SEDHI concept has been selected. The detailed performances of each critical component are provided, focusing on the most critical performances which have been obtained at this level of the Pléiades development.

The micro-opto-electro-mechanical systems (MOEMS), based on mature technologies of micro-electronics, are essential in the design of future astronomical instruments. One of these key-components is the microdeformable mirror for wave-front correction. Very challenging topics like search of exo-planets could greatly benefit from this technology. Design, realization and characterization of micro-Deformable Mirrors are under way at Laboratoire d’Astrophysique de Marseille (LAM) in collaboration with Laboratoire d’Analyse et d’Architecture des Systèmes (LAAS).

In order to measure the surface shape and the deformation parameters during operation of these devices, a high-resolution Twyman-Green interferometer has been developed. Measurements have been done on a tiltable micro-mirror (170*100μm²) designed by LAM-LAAS and realized by an American foundry, and also on an OKO deformable mirror (15mm diameter). Static characterization is made by phase shifting interferometry and dynamic measurements have been made by quantitative time-averaged interferometry. The OKO mirror has an actuator stroke of 370±10nm for 150V applied and its resonant frequency is 1170±50 Hz, and the tiltable mirror has a rotation cut-off frequency of 31±3 kHz.

Solid-state optical sensors are now commonly used in space applications (navigation cameras, astronomy imagers, tracking sensors...). Although the charge-coupled devices are still widely used, the CMOS image sensor (CIS), which performances are continuously improving, is a strong challenger for Guidance, Navigation and Control (GNC) systems. This paper describes a 750x750 pixels CMOS image sensor that has been specially designed and developed for star tracker and tracking sensor applications. Such detector, that is featuring smart architecture enabling very simple and powerful operations, is built using the AMIS 0.5μm CMOS technology. It contains 750x750 rectangular pixels with 20μm pitch. The geometry of the pixel sensitive zone is optimized for applications based on centroiding measurements. The main feature of this device is the on-chip control and timing function that makes the device operation easier by drastically reducing the number of clocks to be applied. This powerful function allows the user to operate the sensor with high flexibility: measurement of dark level from masked lines, direct access to the windows of interest… A temperature probe is also integrated within the CMOS chip allowing a very precise measurement through the video stream. A complete electro-optical characterization of the sensor has been performed. The major parameters have been evaluated: dark current and its uniformity, read-out noise, conversion gain, Fixed Pattern Noise, Photo Response Non Uniformity, quantum efficiency, Modulation Transfer Function, intra-pixel scanning. The characterization tests are detailed in the paper. Co⁶⁰ and protons irradiation tests have been also carried out on the image sensor and the results are presented. The specific features of the 750x750 image sensor such as low power CMOS design (3.3V, power consumption<100mW), natural windowing (that allows efficient and robust tracking algorithms), simple proximity electronics (because of the on-chip control and timing function) enabling a high flexibility architecture, make this imager a good candidate for high performance tracking applications.

The DOBSON SPACE TELESCOPE Project (DST) at the Technical University of Berlin (TUB) believes that micro satellites can be a challenging competitor in the high resolution remote sensing market. Using a micro satellite as basis for a remote sensing platform will dramatically reduce the cost for the end users thereby initiating the predicted remote sensing boom. The Challenging task is that an optic required for a GSD smaller than 1m is much bigger than the given room for secondary payload. In order to break the volume limits of hitchhiker payloads the DST team develops an optical telescope with deployable structures. The core piece of DST is a 20 inch modified Cassegrain optic. Stored during ascend the instrument fits in a box measuring 60 x 60 x 30cm (including telescope and optical plane assembly). After the satellite was released into free space the telescope unfolds and collimates automatically.

We describe our investigations on tuneable, narrowband and frequency stabilised laser heads. The work is motivated by the potentials of highly stable and narrowband laser light sources for a variety of technical and scientific applications and in particular for atomic clocks and high resolution space instruments.

The spatial resolution improvement of Earth observation satellites implies higher CCD readout frequences (at the moment for an instrument such as SPOT 5, typical CCD readout frequency reaches 5MHz for an Earth resolution of 3.5 m and a 60 km swath).

In space applications, analogue electronics for CCD signal processing use specifically developed devices such as ASIC or Hybrid circuits.

Ion Plating deposition technology is investigated for the manufacturing of durable metal-dielectric light absorbers that are compliant with space requirements. Coatings are manufactured using hafnium (Hf) and silica (SiO₂) for layer materials so that the deposition chamber can still be used without any modification for the manufacturing of standard dielectric coatings. Both monochromatic and broad band light absorbers are studied

At the German Aerospace Center in Stuttgart a laser damage test bench is run to evaluate damage thresholds of various optical components. The system setup is based on the current ISO standards 11254 [1-3] for single shot and multiple pulse operation. The laser damage test bench contains two repetitively pulsed laser sources, a Ti:Sapphire and a Nd:YAG laser, operating at wavelengths of 775 nm and 1064 nm, respectively. Harmonic wavelength converters to the visible spectral range are available. Both lasers are supplying the same damage testing rig. Online damage assessment techniques like sensitive scatter probe monitoring and video microscopy monitoring are used. The system is suited and has been tested extensively in the past for dielectric coated optics like beam turning mirrors, reflectors and windows, nonlinear optical components, semiconductors, and laser crystals. The damage test bench is located in a class 10,000 cleanroom environment under a laminar flowbox providing an additional isolation factor of >10³. The tests can also be performed in sealed optical compartments in partial vacuum and under long term irradiation conditions. All experiments are supported by theoretical simulation of laser-material interactions, down to the sub-ps timescale [4].

Improving materials and devices reliability is a major concern to the spatial industry. Results are reported for satellite mirrors-like specimens consisting in oxide-protected metal systems. Optical coatings were deposited by electron beam evaporation.

Mechanical stress fields in multi-layered materials play an important role. The stress state can have far-reaching implications both in kinetics and thermodynamics. Therefore an integrated apparatus with four-point bending equipment was designed. The technique allowed us to exert stress into a film or a system of films on a substrate concurrently with thermal treatment. In order to achieve the first tests performed with the help of the apparatus, various preliminary characterizations were required. The article reports the preliminary micro-mechanical testing of the materials (ultra micro-indentation to evaluate the elastic modulus of the samples materials and wafer curvature technique to determine the specimen residual stress) and the first ageing experiment. Experimental evidence of accelerated ageing under stress is successfully reported.

Within the context of the ESA TRP programme for DARWIN, a Nulling Interferometer Breadboard for the Near-Infrared was developed and tested. Its basic principle is recombining two light beams relying on a highly symmetric optical design (autobalanced Sagnac Core). Two different star simulators have been implemented, based on a) amplitude division and b) on wavefront division. The required achromatic Pi phase shift was implemented using a) dispersive phase shifter, and b) periscopes (geometrical pupil and field rotation). Due to the extremely symmetric optical design, very good star suppression up to 400 000 has been achieved. OPD control better than 1 nm RMS has been demonstrated over hours.

In the framework of the preparation of the Darwin mission, Alcatel Space has been developing a Multi- Aperture Imaging Interferometer (MAI²) for ESA. The main purpose of this activity is to achieve a deep extinction rate, or "nulling", in the laboratory. The performance goal is a 106 nulling of a simulated star. A second objective is to image a planet-like source. The selected operating wavelength is centred around 1.55 microns, with a relative bandwidth of a few percent. The selected function conceptual designs can be updated to the Darwin spectral range (6-18μm).

The Darwin mission is a project of the European Space Agency that should allow around 2015 the search for extrasolar planets and a spectral analysis of their potential atmospheres in order to detect gases and particularly tracers of life. The basic concept of the instrument is a Bracewell nulling interferometer. It allows high angular resolution and high dynamic range. However, this concept, proposed 25 years ago, is very difficult to implement with high rejection factor and has to be demonstrated in laboratory before being applied in space. Theoretical and numerical approaches of the question highlight strong difficulties: - The need for very clean and homogeneous wavefronts, in terms of intensity, phase and polarisation distribution ; - The need for achromatic optical devices working in a wide spectral range (typically 6 to 18 microns for the space mission). A solution to the first point is the optical filtering which has been successfully experimentally demonstrated at 10 microns using a single mode laser. We focus now on the second point and operate a test bench working in the near infrared, where the background constraints are reduced. We present this test bench and the first encouraging results in the 2-4 microns spectral range. We particularly focus on recent optical developments concerning achromatic component, and particularly the beam combiners and the phase shifter, which are key-points of the nulling interferometry principle. Finally, we present the future of this experimental demonstration, in the thermal infrared, covering the real and whole spectral range of Darwin.

TNO TPD has an extensive experience in the realisation of highly stable passive and active opto-mechanical systems. Future missions of ESA like DARWIN [1] rely heavily on these systems such as metrology equipment, delay lines, nulling equipment etc.. The nulling equipment will be used in the Nulling mode of DARWIN in which it will detect Earth-like planets around nearby stars. In the Nulling mode the starlight is dimmed to a factor of 10-6 at the wavelength range of 6 to 18 μm. During the recent years TNO TPD has been strongly involved in the development of nulling equipment such as phase shifters and a nulling breadboard. Also new concepts for nulling have been generated. A prism based phase shifter has been developed that operates in the visible. Nulling depths were achieved near 1000 in a wavelength range of 550 to 750 nm (equivalent DARWIN nulling depth: 105). Limiting effects like vibrations are presently being eliminated by including an optical path difference control loop. With the nulling breadboard a null depth of 400,000 was achieved and a stable null has been realised over several hours. Further work in the near future will be amongst others the phase A study of a nulling instrument GENIE that will operate on the ESO VLTI.

The SPECtro-heliograph for the Transition REgion (SPECTRE) experiment is one of the instruments of the Solar Heliospheric Activity Research and Prediction Program (SHARPP) suite initially foreseen aboard the NASA mission Solar Dynamics Observatory (SDO) of the International Living With a Star (ILWS) program. The scientific objective of the SPECTRE experiment was to characterize the rapid evolution of plasma in the transition region of the solar atmosphere, producing full-disk 1.2 arcsec-resolution images of the solar atmosphere at the very critical 63 nm OV spectral line, characterizing a solar plasma temperature of about 250,000 K. Unfortunately, NASA very recently and unexpectedly, during the instrument Phase A study, decided not to proceed with the realization of SHARPP. The authors of this paper think that all the work done so far in the definition of SPECTRE should not be lost. So, they have decided to summarize in this paper the main characteristics of this instrument and the results of the analysis so far performed: the hope is that in a next future this work can be used again for realizing an instrument having similar characteristics.

SWAP (SWAP (Sun Watcher using Active Pixel System detector and Image Processing) is an instrument that has been selected to fly on the PROBA- 2 technology demonstration platform, a program of the European Space Agency (ESA) to be launched in 2006. SWAP is based on an off-axis degraded Ritchey Chretien telescope that will image the EUV solar corona at 19.5 nm on a specifically fabricated extreme ultraviolet (EUV) sensitivity enhanced CMOS APS detector. The optical design and the optical coatings are derived from the Extreme Ultraviolet Imaging Telescope (EIT) operating on-board SOHO since 1995 [1]. It has been adapted for a single wavelength telescope with off-axis optics. It allows to use smaller optics and filters, with simple internal baffles avoiding external protruding parts. The superpolished optics will receive a multilayer coating that provides spectral selection centred on 19.5 nm and EUV reflectivity in normal incidence. This compact design is specifically adapted for accommodation on PROBA-2, where mass and envelope requirements are very stringent The SWAP PROBA-2 program will be an opportunity to demonstrate this new optical concept, while it will also validate space remote sensing with APS detectors, as well as on-board image processing capabilities. On the science outcomes, SWAP will provide solar corona images in the Fe XII line on a baselined 2-min cadence. Observations with this specific wavelength allow detecting phenomena, such as solar flares or ‘EIT-waves’, associated with the early phase of coronal mass ejections. The SWAP data will complement the observations provided by SOHO-EIT, and STEREOSECCHI. is an instrument that has been selected to fly on the PROBA- 2 technology demonstration platform, a program of the European Space Agency (ESA) to be launched in 2006. SWAP is based on an off-axis degraded Ritchey Chretien telescope that will image the EUV solar corona at 19.5 nm on a specifically fabricated extreme ultraviolet (EUV) sensitivity enhanced CMOS APS detector. The optical design and the optical coatings are derived from the Extreme Ultraviolet Imaging Telescope (EIT) operating on-board SOHO since 1995 [1]. It has been adapted for a single wavelength telescope with off-axis optics. It allows to use smaller optics and filters, with simple internal baffles avoiding external protruding parts. The superpolished optics will receive a multilayer coating that provides spectral selection centred on 19.5 nm and EUV reflectivity in normal incidence. This compact design is specifically adapted for accommodation on PROBA-2, where mass and envelope requirements are very stringent The SWAP PROBA-2 program will be an opportunity to demonstrate this new optical concept, while it will also validate space remote sensing with APS detectors, as well as on-board image processing capabilities. On the science outcomes, SWAP will provide solar corona images in the Fe XII line on a baselined 2-min cadence. Observations with this specific wavelength allow detecting phenomena, such as solar flares or ‘EIT-waves’, associated with the early phase of coronal mass ejections. The SWAP data will complement the observations provided by SOHO-EIT, and STEREOSECCHI.

MIRI (the Mid InfraRed Instrument) is one of the focal plane instruments of the James Webb Space Telescope. The instrument comprises a camera and a spectrometer module. The instrument plays the following key roles in the JWST science program. - Discovery of the “first light”. - Assembly of galaxies: history of star formation, growth of black holes, production of heavy elements. - Formation of stars and planetary systems. - Evolution of planetary systems and conditions for life. The MIRI spectrometer covers the spectral range from 5 – 28.3 μm with a spectral resolution better than 2000. The spectral module is an imaging spectrometer with a field of view ≥ 3 arcsec. The spectrometer consists of 4 spectral channels that share 2 detectors of 1024 × 1024 pixels each. In a single measurement one third of the wavelength range of the channels is imaged onto the detectors. By changing gratings the whole spectral range is covered in 3 measurements. In this paper the optical design of the MIRI spectrometer is described.

MIRI, the mid-IR instrument of JWST (JamesWebb Space Telescope), will include a coronagraphic device for which the ultimate goal is the detection and caracterization of extrasolar planets around nearby stars. In this paper, we describe the optical concept of MIRI and the instrumental choices that were made in phase A and B regarding the coronagraphic system. Finally, we will present numerical simulations that we carried out to evaluate the capability for detecting extrasolar giant gazeous planets.

The COROT mission is dedicated to stellar seismology and search for telluric extra -solar planets. The development is led by CNES in association with French laboratories (LESIA, LAM and IAS) and several European partners (Germany, Belgium, Austria, Spain, ESA and Brasilia). The COROT seismology program will measure periodic variations with amplitude of 2.10-6 of the photon flux emitted by bright stars. The COROT exoplanet program will detect the presence of exoplanets using the radiometric occultation method. The need is to detect photons flux variations about 7.10-4 for one hour integration time. Such performance will permit to detect occultations on a very large number of stars : magnitude between 12 and 15.5. The satellite Preliminary Design Review has been held on January 2004 while the instrument is already in development phase with a Critical Design Review in April 2004 and a delivery of the flight model in March 2005. The launch is scheduled in June 2006. This paper recalls the mission, describes the payload and its main noise performances.

COROTEL is the telescope of the future 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 Space has proposed an original optical concept associated with a high performance baffle. From 2001, the LAM (Laboratoire d’Astrophysique de Marseille, CNRS) has placed the telescope development contract to Alcatel Space and is presently almost finished. Based on relevant material and efficient thermal control design, COROTEL should meet its ambitious performance and bring to scientific community for the first time precious data coming from stars and their possible companions.

Gaia is a cornerstone mission of the European Space Agency, approved with launch by end of 2012, but studied with a programmatic assumption of a launch in the 2010 time frame. Gaia will build an extraordinary precise 3-D map of about one billion stars throughout our Galaxy with an astrometric accuracy of about 10 μas (micro-arcseconds) for a star magnitude V = 15. The initial Gaia design was made in 1998 by Matra-Marconi Space, today EADS-Astrium (France) under ESA contract, awarded in open competition. The concept included two separate telescopes each having a very large focal plane made of about 250 CCDs. The target accuracy of 10 μas for a star magnitude V = 15 was shown to be achievable with available CCD technology and with an instrument envelope compatible with Ariane 5 launcher. In 2002, the initial design was deeply revisited by EADS-Astrium again under ESA contract in view of reducing the programme cost while preserving the science objectives. The reassessed concept still makes use of the same measurement principle but with some major modifications: the size of the instrument has been scaled down so as to enable a Soyuz-Fregat launch, and the two astrometric focal planes were superimposed by using a new optical configuration, therefore reducing the total number of CCDs from 500 to about 200. The paper describes the major evolution of Gaia payload.

The Space Infrared Telescope for Cosmology and Astrophysics (SPICA) mission is a Japanese astronomical infrared satellite project optimized for mid' to far-infrared observatories. It will be launched at ambient temperature and cooled down on orbit by mechanical coolers on board with an efficient radiative cooling system, which allow us to have a 3.5m cooled (4.5K) telescope in space. SPICA will answer a number of important problems in present-day astronomy, ranging from the star-formation history of the universe to the formation of planets, owing to its high spatial resolution and unprecedented sensitivity in the mid- to far-infrared. The large aperture mirror for cryogenically use in space, however, demand a challenging development for the telescope system. A single aperture design of the primary mirror will be adopted for the SPICA telescope rather than deployable mirror designs to avoid further complexity and ensure the feasibility. The number of actuators for the primary mirror, if needed, will be minimized. Silicon carbide and carbon-filter reinforced silicon carbide are extensively investigated at present as the prime candidate materials for the SPICA primary mirror. This presentation reports the current status of the SPICA telescope system development.

The Heterodyne Instrument for the Far-Infrared (HIFI) of the ESA cornerstone mission Herschel is required to operate at wavelengths between 157 and 625 μm. Because of the long-wavelength character, and the complexity and modularity of the optical design, there is a clear need for accurate electromagnetic simulations supported by experimental verification. The need for a compact layout in order to reduce mass and volume as far as possible has important optical consequences. Several mirrors are illuminated in the propagating near-field rather than in the far-field. Consequently the classical geometrical design and analysis approach is inadequate. The long-wavelength character of the system can not be ignored and the associated diffraction effects inevitably become important. In this paper we describe the results of electromagnetic simulations of the optical system for band 1 of HIFI at a wavelength of 625 μm. In order to verify the results of the front-to-end coherent propagation of the detector beams, near-field facilities capable of measuring both amplitude and phase of the electromagnetic field have been developed. A unique feature of these facilities is that the absolute coordinates of the measured field components are known within a fraction of a wavelength. Therefore a true comparison with theoretical predictions can be made. We compare measurement data taken at 625 μm with simulations and discuss to what extent measured and simulated results may be expected to agree. We conclude by presenting the consequences of our observations in terms of system performance.

The cornerstone mission of the European Space Agency (ESA) scientific program Herschel/Planck is currently in the design manufacturing phase (phase C/D). The Planck satellite will be launched in 2007, together with Herschel. Located around the L2 Lagrange point, Planck aims at obtaining very accurate images of the Cosmic Wave Background fluctuations. Working up to high frequency (857GHz, i.e. 350μm wavelength), Planck is expected to give sharper images than the recently launched WMAP satellite. The Planck Telescope is an off-axis (unobscured) Gregorian antenna, with a 1.5m diameter pupil, a small F-number (~1) and a large FOV (+/-5° circular), owing to place a large number of detectors (bolometers) in the focal plane. This paper presents the optical design, performance, and verification concept of the Planck telescope. The custom made sequential Hartmann system is described. Working at 10.6μm, it will directly measure the wavefront of the telescope in cryogenic environment i.e. at operational conditions. This will be a major milestone in the spacecraft development.

PLANCK is a project of the European Space Agency to be launched in February 2007 by an ArianeV rocket with the Herschel Space Observatory . It is designed for imaging the temperature and polarization anisotropies of the millimetre and submillimetre radiation over the whole sky with unprecedented sensitivity, accuracy and angular resolution using 9 frequency channels ranging between 25 and 1000 GHz. The main source at these frequencies is the Cosmic Microwave Background (CMB), i.e. the radiation emitted by the early universe when, about 300000 years old, ionised hydrogen recombined and became transparent from the visible to radio frequencies of the electromagnetic spectrum. The main goal of the PLANCK mission is to retrieve the main cosmological parameters of the Universe with accuracies of a few percent from the observation and analysis of random small contrast (10–4) features in the CMB. The angular power spectrum of the CMB anisotropies is a function of the fundamental cosmological parameters. A proper measurement of all the angular frequencies of the CMB is essential for an accurate interpretation of the data. In consequence the optical performances of Planck will directly impact the ability of retrieving theses parameters. Recent results of the Willkinson Microwave Anisotropy Probe (WMAP) mission show that polarization information of CMB radiation is very challenging, and that the precise measurement of the CMB could completely change the knowledge we have on our universe ([1]). The focal plane assembly (FPA) of the PLANCK telescope is composed of two instruments. The High Frequency Instrument (HFI) of PLANCK is the most sensitive CMB experiment ever planned ([2]). Together with the Low Frequency Instrument (LFI), this will make a unique tool to measure the full sky and to separate various components of its spectrum. This paper describes the main performances of the HFI beams and compares results obtained with 2 different softwares: GRASP8 [3] and an home-made software developed at the Ireland National University of Maynooth [4]. Specials attention will be paid to polarized beams (100, 143, 217, 353 GHz) and multimoded channels (545 and 857 GHz).

Placed on the L2 Lagrangian point, Herschel operates in the spectral range between 80 and 670 μm wavelength and is devoted to astronomical investigations in the far-infrared, sub-millimetre and millimetre wavelengths. The Herschel Telescope is an “all Silicon Carbide” Telescope, based on a 3.5-m-diameter Cassegrain design. The driving requirements are the large diameter (3,5m), the WFE to be kept below 6μrms despite the operational temperature (70K), and finally the mass to be kept below 300kg. The size of the Telescope has put some challenges in the manufacturing and the tests facilities installations. At this stage, the major critical phase which is the brazing of the primary mirror has successfully been passed. The development and manufacturing of the Herschel Telescope is part of the Herschel Planck program funded by the European Space Agency (ESA).

Observatoire de Neuchâtel (ON) has recently started breadboarding activities for an Optically-pumped Space Cesium-beam Atomic Resonator in the frame of an ESA-ARTES 5 project. The goal is to demonstrate a frequency stability approaching σy = 1x10-12 τ-1/2 with the simplest optical scheme (a single optical frequency for both the atomic pumping and detection processes). This development constitutes a fundamental step in the general effort to reduce the mass of the on-board clocks, while keeping or even improving its performances. It will take advantage of previous activities at ON in the late ’80 and of the latest progresses in the field of tunable and narrow-band laser diodes.

Coherent optical intersatellite links for high data rate transmission shall be verified in orbit for the first time in conjunction with the TerraSAR-X mission scheduled for launch in 2005. The Optical Terminals are developed and currently built at Tesat-Spacecom with funding support from the German Space Agency (DLR). Detailed results will be presented on terminal design, performance and program status.

PASTEL embarked on-board SPOT4, French LEO earth observation satellite, and OPALE mounted on-board ARTEMIS, European GEO telecommunication satellite are the key components of SILEX (Semi-conductor Inter-satellite Link Experiment) system. Launched in March 1998, PASTEL terminal was first verified via star tracking. Then, first SILEX optical communication was successfully performed in December 2001 with ARTEMIS at 31000 km. Following 12 months ARTEMIS orbit rising, SILEX commissioning phase was successfully achieved in spring 2003. Today, more than hundred successful optical communications have been achieved. On 1st of October 2003, the SILEX optical link was declared fully operational by the European and French space agencies. After a recall of SILEX architecture, design and onground verification, this paper reports on in-orbit results.

The continuous growth in data rate demand, the importance of real time commanding and real time access to the information for diverse civilian and military applications as well as the in-orbit demonstration of optical communication have led to boost the interest of such systems for future applications. After a presentation of the different fields of application and their associated performances requirements, this paper presents the possible optical link candidates. Then, the architecture, the design and the performances of new optical terminal generations, which profits from SILEX experience and the use of new technologies such as SiC and APS, are detailed. This new optimised generation, highly simplified with respect to SILEX terminals and dimensioned to offer higher data rate, presents attractive mass, volume and power characteristics compatible with a simple accommodation on the host vehicle.

The Space Interferometry Mission, scheduled for launch in 2008, is an optical stellar interferometer with a 10 meter baseline capable of micro-arcsecond accuracy astrometry. A mission-enabling technology development program conducted at JPL, has yielded the heterodyne interferometric displacement metrology gauges required for monitoring the geometry of optical components of the stellar interferometer, and for maintaining stable starlight fringes. The gauges have <20 picometer linearity, <10 micron absolute accuracy, are stable to <200 pm over the typical SIM observation periods (~1 hour), have the ability to track the motion of mirrors over several meters. We discuss the technology that led to this level of performance: lowcross- talk, low thermal coefficient optics and electronics, active optical alignment, a dual wavelength laser source, and a continuously averaging, high data rate phase measurement technique. These technologies have wide applicability and are already being used outside of the SIM project, such as by the James Webb Space telescope (JWST) and Terrestrial Planet Finder (TPF) missions.

In the frame of the CNES R and T activity related to laser metrology, SAGEIS-CSO is actually developing a new smart interferometric sensor, last to arrive in the “MOUSE” family. In this article, we give at first a brief oversight of the MOUSE interferometric concept as well as its performances for two kinds of applications. Secondly, some interesting other set-ups for space applications are mentioned and finally we present modifications that the system will undergo in order to be compliant with long distance measurements. These different developments point out the ability of the MOUSE/IASI interferometric system to be a powerful metrological instrument for space environment.

The ESA DARWIN project uses a set of telescopes based on free flying satellites and operated as an aperture synthesis system. The relative position of all these satellites has to be maintained with a very high accuracy. This is only possible with the help of a very high precision metrology system. We present here in a first part the requirements for the optical metrology of DARWIN and the proposed definition of the metrology systems needed to answer these requirements. In the second part we present the design of the various systems. Eventually we give the results of the performance tests of breadboards that have been manufactured in the framework of the ESA study "High Precision Optical Metrology" to validate these designs.

The MSTAR sensor (Modulation Sideband Technology for Absolute Ranging) is a new system for measuring absolute distance, capable of resolving the integer cycle ambiguity of standard interferometers, and making it possible to measure distance with subnanometer accuracy. The sensor uses a single laser in conjunction with fast phase modulators and low frequency detectors. We describe the design of the system - the principle of operation, the metrology source, beam-launching optics, and signal processing - and show results for target distances up to 1 meter. We then demonstrate how the system can be scaled to kilometer-scale distances and used for space-based applications.

The Space Interferometry Mission (SIM) requires fringe measurements to the level of picometers in order to produce astrometric data at the micro-arc-second level. To be more specific, it is necessary to measure both the position of the starlight central fringe and the change in the internal optical path of the interferometer to a few hundreds of picometers. The internal path is measured with a small heterodyne metrology beam, whereas the starlight fringe position is estimated with a CCD sampling a large concentric annular beam. One major challenge for SIM is to align the metrology beam with the starlight beam to keep the consistency between these two sensors at the system level while articulating the instrument optics over the field of view. The Micro-Arcsecond Metrology testbed (MAM) developed at the Jet Propulsion Laboratory, California Institute of Technology, features an optical interferometer with a white light source, all major optical components of a stellar interferometer and heterodyne metrology sensors. The setup is installed inside a large vacuum chamber in order to mitigate the atmospheric and thermal disturbances. Wide angle astrometric observations are simulated by articulating the optics over the 15 degrees field of regard to generate multiple artificial stars. Recent data show agreement between the metrology and starlight paths to 350pm in the full wide angle field of view of SIM. This paper describes the MAM optical setup, the observation process, the current data and how the performance relates to SIM.

The goal of a cophasing sensor (CS) is to measure the phase disturbances between the sub-apertures or inside each aperture of a telescope. Three CSs are currently studied at ONERA. A first CS for Earth imaging is based on phase diversity on extended sources (cf companion paper by L. Mugnier). A second CS for intercalibration uses phase retrieval on a point source. The third CS for nulling interferometry (“DWARF”, for the ESA/DARWIN mission) is based on similar algorithms. To test performance of these CSs, ONERA has defined and integrated a multipurpose bench, “BRISE”. Its main features are the simultaneous imaging of a point source and of an extended source, the minimisation of absolute and differential disturbances, the use of any aperture configuration and the generation of pure calibrated piston/tip/tilt aberrations on three sub-apertures by a dedicated PZT-based device. Preliminary experimental results are consistent with numerical simulations and confirm nanometric performance.

A compact Interferometric Tomograph has flown on a MASER sounding rocket in spring 2002. This original instrument has been developed by Lambda-X (optics) and the Swedish Space Corporation-SSC (electronics) to measure 3-dimentional temperature (through refractive index) distribution in a liquid while it evaporates though a limited free surface. The tomograph includes 6 interferometers arranged symmetrically around a liquid cell. The paper describes the module and concentrates on the optical beam splitting and combining original systems that have been implemented in the compact instrument; holographic gratings are used to split the sole laser beam into 6 beams and to combine the 6 interferometer views on 2 CCD cameras. Finally, 3-dimentional temperature distributions reconstructed from flight data are presented.

The Fluid Science Laboratory (FSL) is a multiuser facility developed and built by the European Space Agency (ESA). Its launch onboard the Columbus Laboratory, a module of the International Space Station (ISS) is foreseen in June 2005 according to the present planning. FSL can host sequentially Experiment Containers dedicated to a specific experiment in various scientific areas like fluid science, crystal growth, foams and directional solidification within transparent media and, owing to its adaptable diagnostic tools and its modularity on several levels, complementary science areas such as colloid and aerosol physics, particle agglomeration and plasma crystals are envisaged. The visualisation, monitoring and control of the experiment is based on a set of optical diagnostics included in the FSL facility such as visualisation in two perpendicular directions, velocimetry, ESPI and Wollaston interferometry, Schlieren working in transmission and reflection modes, infrared and a high speed camera. The paper will describe the optical tools included in FSL and their performances.

The Protein Crystallisation Diagnostic Facility (PCDF) is a multi-user facility to study the protein crystallisation under the conditions of micro-gravity onboard the International Space Station (ISS) Columbus facility. Large size protein crystals will growth under reduced gravity in thermally controlled reactors. A combination of diagnostic tools like video system, microscope, interferometer, and light scattering device shall help to understand the growth phenomena.

As part of the development of an Experiment Container (EC) for the Fluid Science Laboratory (FSL), to be launched to the International Space Station, a digital holographic microscopy (DHM) system has been breadboarded. The scientific topic of this EC is emulsions, and a large depth of field (DOF) is required. The DHM enables to visualise the drops of emulsions, down to a size of 4 μm, on a DOF which is about 90 times its classical value. All this information is contained in one single image, which is a major advantage in space applications, where the downlink datarate and recording capacity are very limited compared to laboratory conditions. This paper describes the technique being used, presents the application to emulsions, shows tests results including image re-construction, and quantifies the performances as well as the limitations of the system.

DECLIC is a joint CNES/NASA research program to be implemented in the International Space Station (ISS). The facility is dedicated to the study of materials science under microgravity, and the processing operations will take place in an ISS EXPRESS rack from 2006 to 2008. Command and control will be performed from ground thanks to the possibility for scientists to monitor quasi real time images from their space experiment. Its modular design will make it able to accommodate a large variety of experiments. Cells containing the materials are placed together with their specific instrumentation (heaters, actuators, and scientific probes) in inserts that can easily be put in and removed from an experiment locker. The latter provides several illumination sources to the samples, that are used for interferometry or microscopy observations as well as optical transmission or light scattering measurements. These measurements are done in the other side of the locker by different sensors (cameras, photodiode). A second locker provides power, supplies temperature regulation or experiment control as well as data handling. This paper focuses on the optical measurements: it will describe the different sources and sensors available in the facility and give their performance based on models or measurements done on different types of experiments along the qualification process of the engineering model.

Several optical instruments are devoted for diagnostic in physico-chemical experiments, performed in microgravity environment. The aim of this paper is to describe a Wollaston interferometer devoted to measure the refraction index gradient of a transparent liquid media, in order to measure the concentration or temperature gradients around a formed drop. The Wollaston interferometer has been chosen because its sensitivity to the wavefront error can be tuned choosing the shearing component. Moreover this interferometer type has been chosen for his compactness and low sensitivity to the vibrations. This interferometer has been developed for the INEX MAM 3-Welcome project (EADS Space, Bremen / ESA contract), in which two different experiments, one devoted to the execution of the Marangoni migration, the other to the Wetting and Coalescence Prevention, have been carried out during the fly of MAXUS 5 Sounding Rocket.

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. An engineering model development programme verified optical alignment techniques and crucially, demonstrated structural stability through vibration tests. As a result of this, the flight model camera has been assembled at the Space Science and Technology Department of CCLRC's Rutherford Appleton Laboratory in the UK, in preparation for launch in 2005. The camera has been designed to be compact and lightweight so that it may be flown on a low cost mini-satellite (~120kg launch mass). To achieve this, the camera utilises an off-axis three mirror anastigmatic (TMA) 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; RAL (Rutherford Appleton Laboratory), SSTL (Surrey Satellite Technology Ltd.), QinetiQ and Infoterra. Its objective is to demonstrate provision of rapid response high-resolution imagery to fixed and mobile ground stations using a low cost mini-satellite. This paper describes the opto-mechanical design, assembly and alignment techniques implemented and reports on the test results obtained to date.

ONERA is currently conducting a study on the feasibility of an imaging interferometer for Earth observation from a GEO orbit. During this study, some key elements for the definition of such an instrument have been identified and studied. The results obtained so far confirm the applicability of wide-field optical interferometry with a Michelson-type instrument for Earth observation from a GEO orbit.

Future space missions rely on the availability of space qualified high precision optical metrology instruments like ultra stable laser sources. Here, we present a compact, frequency-doubled, monolithic Nd:YAG laser (non planar ring-oscillator, NPRO), frequency stabilized to a hyperfine transition in molecular iodine, based on the method of modulation transfer spectroscopy. Using a 10 cm long iodine cell cooled to 1±C and a total light power of ~ 5 mW a frequency stability of 1 • 10^-12 for an integration time of τ = 1 s and 3 • 10^-13 for τ < 100 s was achieved. By use of an active offset compensation (offset compensation by amplitude modulated sidebands, OCAMS), the frequency stability of this setup was furthermore improved to 4 • 10^-14 for τ > 5000 s. This setup therefore fulfillls the basic metrological requirements for the LISA and Darwin missions (with potential beyond). Due to very compact construction, it serves as a study and demonstrator for a future space qualified iodine standard.

EarthCARE is one of the three candidate Earth Explorer Core Missions of the ESA Living Planet Programme. It will address the interaction and impact of clouds and aerosols on the Earth’s radiative budget. ATLID (ATmospheric LIDar), one of the four instruments of EarthCARE, shall determine vertical profiles of clouds and aerosols physical parameters (altitude, optical depth, backscatter ratio and depolarisation ratio) in synergy with other instruments. Operating in the UV range at 355 nm, ATLID provides atmospheric echoes with a vertical resolution of 100 m from ground to an altitude of 30 km. Thanks to a high spectral resolution filtering, the lidar is able to separate the relative contribution of aerosol (Mie) and molecular (Rayleigh) scattering, which gives access to aerosol optical depth. The following addresses the current instrument design as worked-out by Astrium during the EarthCARE Phase-A Study, which was was run in 2002-2003 under ESA contract. Besides the basic architecture trade-offs, the emphasis is put on some major technical and technological choices that were done to optimise the lidar performances and efficiency.

Last decade EADS-ASTRIUM and its partner Boostec, has become world leader in the field of Silicon Carbide (SiC) optical payloads. In the framework of earth and scientific observation, high and very high-resolution optical payloads have been developed. This leadership allowed EADS-ASTRIUM to propose a large and complete range of space-based system for optical observation. Ceramic mirrors and structures are becoming attractive for high precision light weighted opto-mechanical applications. Developments over the past 15 years by EADS-ASTRIUM and by Boostec have demonstrated the feasibility and versatility of the SiC material for numerous applications. The most favorable characteristics of this material are high stiffness, high thermal conductivity and low thermal expansion (CTE). Furthermore, SiC allows relatively quick and cheap manufacturing of components because the components can be shaped with conventional tools in a milling process of the green body material. Through different joining processes, SiC allows for large size applications and systems. Only the scale of the available production facilities, the largest of which currently is 4 m in diameter, limits size of the structures and mirrors that can be manufactured.