The ESA/JAXA SPICA mission is a candidate for the ESA Cosmic Vision Medium Class M5 opportunity. Since 2019 an Airbus Defence and Space team has been performing a trade-off study (on behalf of ESA) to establish a baseline telescope optical configuration and design, which can meet the mission scientific performance requirements. This paper describes the telescope baseline design selected, with first estimates of the expected optical performance. The optical design wavelength is 20 microns for an operating temperature of 8 K covering a total bandwidth of 12 to 420 microns over a 30 arc minutes field of view, with a total required collecting area of at least 4.0 m². The fundamental mission science driver is to achieve a sky background (astrophysical sources) limited performance. The telescope is designed to illuminate three instruments namely; SMI (JAXA - Japan), SAFARI (SRON - Netherlands) and B-BOP (CEA - France).
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.
Ceramic mirrors and structures have become extremely attractive for high precision light weighted optomechanical applications. Developments over the past years by Boostec and EADS-Astrium have demonstrated the feasibility and versatility of the Sintered SiC material for numerous applications. The incomparable properties of the Boostec® Silicon Carbide material combined with more than 20 years efforts to develop a large range of joining processes, allows for large size light weighed space applications and systems. In the framework of earth and scientific observation, high and very high-resolution optical payloads have been developed by EADSAstrium and its partner Boostec. Since the beginning of this new century, seven SiC instruments have been launched; they are successfully operating in space. More than ten instruments are under development, most of them being already tested and qualified. It means the manufacturing and testing of more than 150 SiC mirrors and structural parts for space applications under environmental conditions varying from 300 K to a few Kelvin. This unique experience acquired by EADS-Astrium and its partner allows now to propose the Boostec SiC technology for the benefit of a large and complete range of space-based system for optical observation.
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).
This paper, “Silicon carbide technology for large submillimeter space based telescopes," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.
L. Mazuray, J.-C. Barthès, F. Bayle, D. Castel, P. Claviere, F. Delbru, P.-O. Doittau, L. Gladin, P. Guilleux, S. Halbout, D. Lavielle, J.-L. Varin, S. de Zotti, C. Rosolen, H. Ozeki
An acousto-optical spectrometer (AOS) is employed in order to meet scientific mission objectives of submillimeter-wave limb-emission sounder (SMILES) to be aboard the Japanese Experiment Module (JEM) of International space station (ISS). AOS is developed by ASTRIUM for the Japanese space agency (NASDA). The capability of multi channel detection with AOS is suitable for observing multi-chemical species in a wide frequency region. Low noise of the AOS enables us to obtain the spectra with a very high sensitivity. Several technical concerns relating to important instrumental characteristics of AOS are discussed and expected performance of the design are overviewed.
The international Rosetta mission, now planned by ESA to be launched in January 2003, will provide a unique opportunity to directly study the nucleus of comet 46P/Wirtanen and its activity in 2013.
We describe here the design, the development and the performances of the telescope of the Narrow Angle Camera of the OSIRIS experiment et its Silicon Carbide telescope which will give high resolution images of the cometary nucleus in the visible spectrum. The development of the mirrors has been specifically detailed.
The SiC parts have been manufactured by BOOSTEC, polished by STIGMA OPTIQUE and ion figured by IOM under the prime contractorship of ASTRIUM. ASTRIUM was also in charge of the alignment. The final optical quality of the aligned telescope is 30 nm rms wavefront error.
For Herschel SiC primary mirror purpose, a new approach of comparative CTE measurement has been developed; it is based on the well known bimetallic effect (“biceramic” in this case) and also optical measurements. This method offers a good CTE comparison capability in the range of 170-420K (extensible to 5-420K) depending of the thermal test facilities performance, with a resolution of only 0.001 μm/m.K. The Herschel primary mirror is made of 12 SiC segments which are brazed together. The CTE of each segment has been compared with the one of a witness sample and no visible change, higher than the measurement accuracy, has been observed. Furthermore, a lot of samples have been cut out from a spare segment, from different places and also from all X, Y and Z direction of the reference frame. No deviation was seen in all of these tests, thus demonstrating the very good homogeneity, reproducibility and isotropy of the Boostec® SiC material. Some recent literature about SiC material measurements at cryogenic temperature shows a better behaviour of Boostec® SiC material in comparison with other kind of SiC which are also candidate for space optics, in particular for isotropy purpose. After a review of the available literature, this paper describes the comparative CTE measurement method and details the results obtained during the measurement campaigns related to Herschel project.
Euclid is a part of the European Space Agency Cosmic Vision program. Euclid mission’s goal is to understand the origin of the accelerating expansion of the Universe. This space mission will embark a 1.2 m Korsch telescope, a visible imager (VIS) and a near-infrared spectrometer and photometer (NISP).
In the scope of EUCLID spatial mission, NISP instrument requires high positioning accuracy and high dimensional stability to achieve the required optical performances. LAM is in charge of the development of the instrument main structure which is based on silicon carbide material technology and allows the accurate positioning and maintain of the optomechanical concept sub-systems. This article presents the main steps of this development. It describes the challenging design of this mechanical concept. The associated finite element model, demonstrating the thermomechanical strength of the structure, is presented. Spatial environment vibrations tests performed on the hardware are explained and detailed: requirements, instrumentation and test methodology with the introduction of notching. Finally, the correlation study between finite element analyses and tests is exposed.
Placed on the Sun-Earth L2 Lagrange point, SPICA will operate in the 5 to 210 μm wavelength range. Astrium has been
contracted by ESA/ JAXA to update the study of the SPICA telescope from a 3.5 m design (compatible to the Japanese
HIIB launcher) to a 3.2 m design (compatible to the HII-A with the short 5S fairing): despite a similar fairing diameter,
the shorter length of the fairing envelope results in a reduction of the M1-M2 distance and an associated diameter
reduction of M1. Maximization of the M1-M2 distance within the constraints is important to maintain a reasonable
polishing criteria of the main reflector. Therefore the M2 assembly sizing and the back focal length become main
parameters for the telescope optical design. The main constraints are driven by the telescope requirements such as focal
length, maximizing the diameter of M1 (3.2 m) and, M1 f-number (critical for the manufacturing aspects). The WFE
must be below 350 nm rms, and operational temperature below 6K. .
The main issues addressed in this paper are:
- an improved telescope design based on the Astrium background in Silicon Carbide technology which has been tried-an-tested
for mirrors and structural parts on several space projects, including HERSCHEL and Gaia (brazing, polishing,
assembling, iso-static mountings).
- performances which are taking advantage of the SiC properties ,such as homogeneity of the single-phase material
inside the structure, and structural stability from ambient to the operational temperature range. Our study shows that the
SiC telescope design can fulfil all the mechanical and optical requirements for SPICA.
- the verification and optical tests definition which will be key elements in the qualification of the telescope to be
incorporated in the logic of the satellite verification activity to be conducted in Japan.
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 "allSilicon Carbide" Telescope, based on a 3.5-m-diameter Cassegrain design. The driving requirements are the large diameter (3;5m) which represents a manufacturing challenge, the WFE to be kept below 6μrms despite the operational temperature of 70K, and finally the mass to be kept below 300kg. The size of the Telescope has put some challenges in the manufacturing processes and the tests facilities installations. At this stage, the major critical phases which are the brazing and the grinding of the primary mirror have 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).
The international Rosetta mission, now planned by ESA to be launched in January 2003, will provide a unique opportunity to directly study the nucleus of comet 46P/Wirtanen and its activity from a heliocentric distance of 3.2 AU to the perihelion passage at 1.06 AU in July 2013. We describe here the design, the development and the performances of the telescope of the Narrow Angle Camera of the OSIRIS experiment which will give high resolution images of the cometary nucleus in the visible spectrum.
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