METimage is a cross-purpose, medium resolution, multi-spectral optical imaging radiometer for meteorological applications onboard the MetOp-SG satellites. It is capable of measuring thermal radiance emitted by the Earth and solar backscattered radiation in 20 spectral bands from 443 to 13.345 nm. We provide an overview over the instrument design and present the instrument development status.
Accurate prediction of the arrival of solar wind phenomena, in particular coronal mass ejections (CMEs), is becoming more important given our ever-increasing reliance on technology. SCOPE is a coronagraph specifically optimised for operational space weather prediction, designed to provide early evidence of Earth-bound CMEs. In this paper, we present results from phase A/B1 of the instrument’s development, which included conceptual design and a program of breadboard testing.
We describe the conceptual design of the instrument. In particular, we explain the design and analysis of the straylight rejection baffles and occulter needed to block the image of the solar disc, in order to render the much fainter corona visible. We discuss the development of in-house analysis code to predict the straylight diffraction effects that limit the instrument’s performance, and present results, which we compare against commercially available analysis tools and the results from breadboard testing. In particular, we discuss some of the challenges of predicting straylight effects in this type of instrument and the methods we have developed for overcoming them.
We present the test results from an optical breadboard, designed to verify the end-to-end straylight rejection of the instrument. The design and development of both the breadboard and the test facility is presented. We discuss some of the challenges of measuring very low levels of straylight and how these drive the breadboard and test facility design. We discuss the test and analysis procedures developed to ensure a representative, complete characterisation of the instrument’s straylight response.
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.
For the DARWIN mission the extremely low planet signal levels require an optical instrument design with utmost efficiency to guarantee the required science performance. By shaping the transverse amplitude and phase distributions of the receive beams, the singlemode fibre coupling efficiency can be increased to almost 100%, thus allowing for a gain of more than 20% compared to conventional designs. We show that the use of "tailored freeform surfaces" for purpose of beam shaping dramatically reduces the coupling degradations, which otherwise result from mode mismatch between the Airy pattern of the image and the fibre mode, and therefore allows for achieving a performance close to the physical limitations. We present an application of tailored surfaces for building a beam shaping optics that shall enhance fibre coupling performance as core part of a space based interferometer in the future DARWIN mission and present performance predictions by wave-optical simulations. We assess the feasibility of manufacturing the corresponding tailored surfaces and describe the proof of concept demonstrator we use for experimental performance verification.
The European DARWIN mission aims at the detection of Earth-like exo-planets and at the spectroscopic characterization of their atmospheres. By nulling interferometry in the mid-infrared wavelength regime the stellar flux may be rejected. By spatial and temporal modulation of the interferometer’s receive characteristic the planet signal may be extracted from the background signals. The DARWIN instrument consists of a flotilla of free-flying spacecraft, three to four spacecraft carrying the collector telescopes and one spacecraft carrying the control units and the beam recombination and detection unit. We present different system design concepts for the DARWIN instrument which have been elaborated within the DARWIN System Assessment Study. We discuss various aperture configurations and beam routing schemes as well as modulation methods and and beam recombination schemes.
EUCLID, a medium-class mission candidate of ESA's Cosmic Vision 2015–2025 Program, currently in Definition Phase (Phase A/B1), shall map the geometry of the Dark Universe by investigating dark matter distributions, the distance-redshift relationship, and the evolution of cosmic structures. EUCLID consists of a 1.2 m telescope and two scientific instruments for ellipticity and redshift measurements in the visible and nearinfrared wavelength regime. We present a design concept of the EUCLID mission which is fully compliant with the mission requirements. Preliminary concepts of the spacecraft and of the payload including the scientific instruments are discussed.
Design, integration, test setup, test results, and lessons-learnt of a high precision laser metrology demonstrator for dual absolute and relative laser distance metrology are presented. The different working principles are described and their main subsystems and performance drivers are presented. All subsystems have strong commonalities with flight models as of LTP on LISA Pathfinder and laser communication missions, and different pathways to flight models for varying applications and missions are presented. The setup has initially been realized within the ESA project "High Precision Optical Metrology (HPOM)", originally initiated for DARWIN formation flying optical metrology, though now serves as demonstrator for a variety of future applications. These are sketched and brought into context (PROBA-3, IXO onboard metrology, laser gravimetry earth observation missions, fundamental science missions like LISA and Pioneer anomaly).
EUCLID is a mission to accurately measure the accelerated expansion of the universe. It has been selected for implementation with a launch planned for 2020. EUCLID will map the large-scale structure of the Universe over 15.000 deg2 of the extragalactic sky and it will measure galaxies out to redshifts of z=2 EUCLID consists of a 1.2 m telescope and two scientific instruments for ellipticity and redshift measurements in the visible and near infrared wavelength regime.
We present a design for the EUCLID space segment, targeting optimum performance in terms of image quality and stability and maximum robustness with respect to performance, resources and instrument interfaces.
The detection of terrestrial exo-planets in the habitable zone of
Sun-like stars as well as the proof of biomarkers
is one of the most exciting goals in Astrophysics today. A nulling interferometer operated in the mid-infrared wavelength regime allows for overcoming the obstacles of huge contrast ratio and small angular separation between star and planet. Dedicated missions, as ESA's DARWIN or NASA's TPF-I, are implemented as a closely controlled formation of free-flying spacecraft which carry the distributed payload. We discuss various implementation alternatives and present an optimized design of the DARWIN instrument
including the science payload and the formation-flying subsystem. We analyze the achievable scientific performance
of the DARWIN instrument by taking into account the target properties and the instrument performance. We show that the DARWIN mission is feasible and that the mission goals can be fulfilled.
Spectroscopy of exoplanets around near-by stars is one of the most fascinating but also most challenging science goals of
our days. The ESA DARWIN mission as well as NASA TPF-I rely on nulling interferometry. The measurement
principle underlying their nulling science mode is essentially nonlinear. On the one hand in terms of null depth as a
function of amplitude and phase noise, and on the other hand in terms of fiber coupling as function of science beam
pointing and lateral offset. We present a performance breakdown and an end-to-end performance simulation for
DARWIN with focus on principal limitations, and with a clear distinction between static null depth contributors,
dynamic error contributors, and so-called instability noise within the overall system. We additionally discuss the derived
next-step development efforts for critical subsystems.
The missions DARWIN and TPF-I (Terrestrial Planet Finder-Interferometer) aim at the search and analysis of
terrestrial exo-planets orbiting nearby stars. The major technical challenge is the huge contrast ratio and the
small angular separation between star and planet. The observational method to be applied is nulling interferometry.
It allows for extinguishing the star light by several orders of magnitude and, at the same time, for resolving
the faint planet.
The fundamental performance of the nulling interferometer is determined by the aperture configuration, the
effective performance is driven by the actual instrument implementation. The x-Array, an aperture configuration
with 4 telescopes allowing for phase chopping and decoupling of the nulling and imaging properties, provides
highest instrument performance. The scientific goals necessitate an instrument setup of high efficiency and utmost
symmetry between the beams concerning optical path length, beam profile and state of polarization. Non-planar
spacecraft formations allow for a simpler spacecraft design which comes at the cost of inherent constellation and
beam asymmetry, of increased complexity of the beam relay optics and of instrumental errors synchronous to
the planet signal demodulation frequency. Planar formations allow for perfect efficiency and symmetry but need
deployable structures for the secondary mirror and the sunshield due to launcher accommodation constraints.
We present a discussion of planar and non-planar implementations of the x-Array aperture configuration and
identify for both the critical items and design drivers. We compare the achievable instrument performance and
point out the constraints for each spacecraft formation.
The DARWIN mission of ESA will search for earth-like exo-planets orbiting suitable target stars in our solar neighborhood, and will allow direct low resolution spectroscopy of exo-planetary atmospheres. The optical enabling technology for DARWIN is high-contrast destructive Nulling interferometry of stellar light, necessitating utmost symmetry of optical beam trains. We report the system driven design of a cryogenic optical delay line compatible with the extremely tight requirements imposed by optical symmetry. After analysis of requirements and system aspects, we describe the actual design implementations and our validation scheme. We conclude with an outlook on integration of this ODL into a cryogenic ground-based testbed for DARWIN Nulling interferometry.
The European DARWIN mission aims at detection and characterization of Earth-like exo-planets as well as at aperture synthesis imaging. The method to be applied is nulling interferometry in the mid-infrared wavelength regime. The DARWIN instrument consists of a flotilla of free-flying spacecraft, one spacecraft carrying the optics for beam recombination and three or more spacecraft carrying the large collector telescopes. We provide a trade-off of different configuration, payload, and mission concepts. We discuss various two and three-dimensional aperture configurations with three or four telescopes, beam routing schemes, phase modulation methods, and beam recombination and detection schemes as well as different launch vehicle configurations, launch scenarios, and orbits. We trade the different DARWIN concepts by assessing the performance in terms of science return, development risk, and planning.
Within the scope of the DARWIN Technology and Research Programme, the European Space Agency (ESA) initiated the development of a dynamic system simulator (called FINCH "Fast Interferometer Characterization") for the spaceborne nulling interferometry mission DARWIN.The FINCH project is realized by two parallel activities:
(1) a simulator for the Guidance, Navigation and Control (FINCH/GNC) of the free-flying satellite array, and (2) a simulator for the optical subsystems and the beam propagation within the system (FINCH/OPT). While the GNC activity is handled by EADS Astrium, France, the optical part is performed in a joint effort by EADS Astrium, Germany, and the European Southern Observatory (ESO).
In this paper we focus on FINCH/OPT aspects and describe:
• DARWIN and the corresponding overall end-to-end simulation approach
• the completed FINCH/OPT development for modelling of point sources
• modelling of extended objects, exact and with suitable approximations
• details of optical modelling of DARWIN configurations within FINCH
• applications of FINCH
This paper quantifies the expected gain in the process window of 150nm structures printed with DUV for alt PSM vs. COG masks and HT PSM. Most of the analysis was performed for dense lines and isolated lines using lithography simulation. Alt PSM show an increase of dose latitude by 9 percent and an improved DOF by 0.2 micrometers for dense liens. For isolated lines the real advantage is seen in the increase of DOF by 0.7 micrometers . Furthermore it will be demonstrated, that alternating PSM can improve the imagin performance of contacts significantly over competitive techniques. Chromeless PSM may push the ultimate resolution limit. However to vary the linewidth three adjacent quartz edges must be used, since two phase edges are instable in defocus. A phase shifting region needs to exceed a minimum width in order to enhance the contrast of the aerial image of the whole feature. Experimental data and simulations show that the required minimum phase-shifter width for an isolated line is in the region of 400nm. Simulation and experiment show, that 90 degrees edges are very sensitive to defocus and neighboring patterns. Using a 3D mask simulator, correction values for etch depth and parameters for a lateral underetch were determined in order to achieve intensity balancing for alt PSM for various feature sizes.