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In these proceedings, we first give a brief overview the instrument design. We then explain the calibration strategy, which is a combination of on-ground and in-flight calibration measures. The on-ground calibration is presented in more detail. It aims to create a complete baseline calibration of the EnMAP instrument comprising a radiometric, spectral, geometric, polarimetric and straylight characterization. In orbit, a diffuser is used for absolute radiometric calibration via sun viewing. On-board calibration light sources ensure radiometric stability in between sun-viewings and spectral stability over the mission lifetime.
Finally, we share first characterization data which are prototypical of the final instrument calibration.
The hyperspectral imager of the Environmental Mapping and Analysis Program (EnMAP) satellite mission comprises two spectrometers whose entrance slits are realized by an all-silicon, highly integrated double slit device. It is manufactured by use of micro-machining and lithographic processes, reaching sub-micron geometric precision. Each slit aperture is 24 μm x 24 mm large, corresponding to an aspect ratio of 1:1000. In some critical respects – such as planarity or coalignment – the technology excells established manufacturing technologies like metal electroforming, milling and others.
In addition to slit aperture definition, the double slit device achieves field separation for the two imaging spectrometers. One of the two transmitted light beams is deflected by a flat mirror. The minute silicon mirror is completely integrated into the device. The EnMAP slit assembly has undergone an intensive qualification test program. Included were vibrational, shock and thermal load tests as well as a more specific sun intrusion test. The results of these tests are briefly presented and discussed.
The instrument features a telescope with a 18cm aperture. A double-slit splits the field of view into the two separate fields for VNIR and SWIR. Two spectrometers disperse the light using large, curved prisms and collect the light in an Offner configuration onto the VNIR and the SWIR detector. In addition, the instrument features calibration capabilities using a deployable, full aperture solar diffuser in front of the telescope and on-board calibration sources that can be fed into the spectrometers. The instruments demanding requirements on thermal stability are covered by an active thermal control of the whole instrument using loop-heat pipes.
In this proceeding, we give a short overview on the design, application and current integration status of the mission, which is currently in Phase D. The focus is on the important steps recently accomplished or currently ongoing, specific on the:
The present situation suggests an EnMAP launch by the end of 2020.
The entire satellite is designed and built by OHB-Systems.
Characterizing and calibrating a state-of-the-art hyperspectral instrument as the EnMAP HSI requires to establish measurement setups that outperform the test object in all relevant performance aspects to achieve the required measurement accuracies.
At the same time technical as well as economical considerations yield to develop measurement equipment that can support multiple use cases throughout the Alignment integration and Test (AIT) Process of the Instrument.
This paper reports on development and commissioning activities of optical ground support equipment (OGSE) for full aperture testing of the EnMAP HSI. Design requirements as well as measured setup performance is reported.
The overall OGSE-system has been set-up and commissioned at OHB in Oberpfaffenhofen. It supports the following measurement cases:
The OGSE consists of several modules. The core component, a highly stable diffraction-limited 200 mm Collimator including a movement system and a scene generator was designed and built by Bertin Technologies upon OHB specifications.
In this proceeding, we give an overview of the design and current integration status of the HSI instrument optical unit with additional focus on measured optical and electro-optical performance.
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