METimage is an advanced multispectral radiometer for weather and climate forecasting developed by Airbus Defence & Space under the auspices of the German Space Administration (DLR) for the EUMETSAT Polar System-Second Generation (EPS-SG). The instrument is equipped with a continuously rotating scan mirror with a 1.7s period followed by a static telescope. The scan mirror permits an extended Earth view of 108° per revolution and regular views to on-board calibration sources. A derotator assembly, which is half-speed synchronised with the scanner, is inserted in the optical beam after the telescope to compensate the image rotation in the focal plane. The derotator optical arrangement is a five-mirror concept that minimises the polarisation sensitivity. The derotator design is constrained by optical performance, mass and compactness, which led to the selection of a full silicon carbide (SiC) concept. The stringent alignment requirements of the derotator optics lead to an excellent pointing accuracy, confirmed by the measurements performed with a dedicated OGSE. The measured wavefront error of the system is very small, thanks to fine polishing of the five optics. In this paper, we will present the overall design of the derotator, discuss the manufacturing of the key SiC elements and present the results of the FM1 test campaign.
AMOS has recently completed the on-site erection and performance evaluation campaign of the 2.5m telescope that is installed on Mount Abu (India) for the Physical Research Laboratory. The 20-m-focal-length telescope has a Ritchey-Chrétien optical configuration. It is equipped with a primary active mirror; an active positioning of the secondary mirror and a first order adaptive optical system. It operates in the 0.37-4 μm spectral range. The project fulfillment relies on the AMOS multidisciplinary expertise in design; manufacturing and verification of high-accuracy optical; mechanical and opto-mechanical systems. This paper presents the assembly; integration; alignment and verifications carried out on site. The alignment relies on the coma-free point method. The end-to-end telescope performances (image quality; pointing; tracking) are measured on sky using the verification instrument in combination with wavefront-curvature sensing and lucky imaging techniques.
Before the transport of a large telescope on site, it is suitable to perform factory tests to guarantee the optical performances. AMOS SA has been awarded of the contract from the design to on-site installation (in Rajasthan) of the 2.5-m Class Telescope for Physical Research Laboratory. The 20-m-focal-length telescope has a Ritchey-Chrétien optical configuration and provides at Cassegrain location one axial port and two side ports. It is equipped with a primary active mirror and a first order adaptive optical system. It operates in the 0.37-4 μm spectral range. The project fulfillment relies on the AMOS multidisciplinary expertise in design and manufacturing of high-accuracy optical, mechanical and opto-mechanical systems. This paper presents the test results carried out at AMOS factory to assess the telescope performances (e.g. active optic control loop, pointing, tracking). It relies on extensive tests on the mount control, and the optical and mechanical sub-systems before assembly.
METimage is an advanced multispectral radiometer for weather and climate forecasting developed by Airbus Defence & Space under the auspices of the German Space Administration (DLR) for the EUMETSAT Polar System –Second Generation (EPS-SG). The instrument is equipped with a continuously rotating scan mirror with a 1.7s period followed by a static telescope. The scan mirror permits an extended Earth view of 108° per revolution and regular views to on-board calibration sources. A derotator assembly, which is half-speed synchronised with the scanner, is inserted in the optical beam after the telescope to compensate the image rotation in the focal plane. The derotator optical arrangement is a fivemirror concept that minimises the polarisation sensitivity. The derotator design is constrained by optical performance, mass and compactness, which led to the selection of a full silicon carbide (SiC) concept. This paper describes the preliminary design and verification approach of the derotator optics.
EUCLID is an optical/near-infrared survey mission to be launched towards the L2 Lagrange point. It will aim at studying the dark universe and providing a better understanding of the origin of the accelerating expansion of the universe. Through the use of cosmological sounding, it will investigate the nature of dark energy, dark matter and gravity by tracking their observational signatures on the geometry of the universe and on the cosmic history of large structures formation. The EUCLID PayLoad Module (PLM) consists of a 1.2 m-class telescope and will accommodate two instruments. As a subcontractor of AIRBUS Defence and Space, AMOS is responsible for the manufacturing of all the silicon carbide mirrors of EUCLID PLM except for the primary mirror. In addition, AMOS also produces the 1.3 m test collimator that is used for the on-ground validation of the optical performances of the payload module under operational thermal vacuum conditions. The 1.3m collimator is designed, manufactured, assembled and tested by AMOS. It is based on a Ritchey-Chretien optical configuration, with a f/2 primary mirror and a hyperbolic secondary mirror. The mirrors are made of ZERODUR and polished by AMOS. The high performance of EUCLID PLM calls for not less demanding requirements for the test collimator, in terms of image quality, thermal stability, line of sight stability under micro-vibration, etc. Here after are presented at first the design and the strategies elaborated to cope with the stringent requirements. Then, the manufacturing and metrology of the mirrors are reported. Finally, the Assembly, Integration and Verification by test (AIV) are discussed.
EUCLID is an optical/near-infrared survey mission to be launched towards the L2 Lagrange point. It will aim at studying the dark universe and providing a better understanding of the origin of the accelerating expansion of the universe. Through the use of cosmological sounding, it will investigate the nature of dark energy, dark matter and gravity by tracking their observational signatures on the geometry of the universe and on the cosmic history of large structures formation. The EUCLID PayLoad Module (PLM) consists of a 1.2 m-class telescope and will accommodate two instruments. As a subcontractor of AIRBUS Defence and Space, AMOS is responsible for the manufacturing of all the silicon carbide mirrors of EUCLID PLM except for the primary mirror. In addition, AMOS also produces the 1.3 m test collimator that is used for the on-ground validation of the optical performances of the payload module under operational thermal vacuum conditions. The 1.3m collimator is designed, manufactured, assembled and tested by AMOS. It is based on a Ritchey-Chretien optical configuration, with a f/2 primary mirror and a hyperbolic secondary mirror. The mirrors are made of ZERODUR® and polished by AMOS. The high performance of EUCLID PLM calls for not less demanding requirements for the test collimator, in terms of image quality, thermal stability, line of sight stability under micro-vibration, etc. Here after are presented at first the design and the strategies elaborated to cope with the stringent requirements. Then, the manufacturing and metrology of the mirrors are reported. Finally, the Assembly, Integration and Verification by test (AIV) are discussed.
The ESA Sentinel-2 mission developed by EADS Astrium will be devoted to Earth high resolution spectral imagery for the purpose of a global environmental monitoring. As a subcontractor of EADS Astrium, AMOS was responsible for the manufacturing of the instrument telescope mirrors and for the validation of the telescope alignment procedure. This paper details the mirror manufacturing sequences from mirror CVDSiC cladding to surface figuring and coating, outlining the metrology steps and their corresponding accuracy budget. The telescope alignment process is described in connection with the tooling and techniques that helped achieve the required optical performance of less than 90 nm RMS wavefront error within the telescope field of view.
Regarding Earth observation missions, it has become unnecessary to point out the importance of making available wide field of view optical instruments for the purpose of spectral imaging.
Taking advantage of the pushbroom instrument concept with its linear field across the on-ground track, it is in particular relevant to consider front-end optical configurations that involve an all-reflective system presenting inherent and dedicated advantages such as achromaticity, unobscuration and compactness, while ensuring the required image quality over the whole field.
The attractiveness of the concept must be balanced with respect to the state-of-the-art mirror manufacturing technologies as the need for fast, broadband and wide field systems increases the constraints put on the feasibility of each individual component.
As part of an ESTEC contract, AMOS designed, manufactured and tested a breadboard of a four-mirror wide field telescope for typical Earth observation superspectral missions.
The initial purpose of the development was to assess the feasibility of a telecentric spaceborne three-mirror system covering an unobscured rectangular field of view of 26 degrees across track (ACT) by 6 degrees along track (ALT) with a f-number of 3.5 and a focal length of 500 mm and presenting an overall image quality better than 100 nm RMS wavefront error within the whole field.
In the framework of the Fluorescence Explorer (FLEX) phase A/B1 study, an elegant breadboard (EBB) of an imaging spectrometer is designed, manufactured and aligned by AMOS, with Airbus Defence&Space as the prime Contractor of the study. The FLEX mission is one of the two candidates of the 8th Earth Explorer mission. The main constituting instrument of the FLEX mission is an imaging spectrometer observing vegetation fluorescence and reflectance with a high- and a low-resolution channels in the 500 nm -780 nm band. As part of the system feasibility study of the mission, a breadboard of the high-resolution channel of the instrument is designed and manufactured with a high representativeness of a future flight concept. The high-resolution channel is referred to as FIMAS (Fluorescence IMAging Spectrometer). The main purpose of the EBB is to demonstrate (1) the manufacturability of the instrument and (2) the compliance of the optical performances with respect to the science requirements (including spatial and spectral resolution and stray-light).
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