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.
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 is presented as a continuation of the ICSO 2018 paper to describe the detailed design and early physical model results of the derotator optics.
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