Versatile full aperture illumination OGSE Setup for alignment and end-to-end calibration of the EnMAP hyperspectral image

The EnMAP hyperspectral Imager (HSI)¹ will allow to acquire Images of the Earth surface in a push broom configuration. 230 wavelength bands between 420nm and 2450nm are simultaneously recorded with a ground resolution of 30m x 30m. 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:<ul> </ul> • Double-pass wave front measurement of the HSI-Telescope for alignment to the HSI-Spectrometer Module<ul> </ul> • Line of sight characterisation of the HSI with sub-arcsecond accuracy<ul> </ul> • Scanning knife edge modulation transfer function (MTF)-Measurement of the HSI in the entire field-of-view<ul> </ul> • Spectral response characterisation of the HSI in the entire spectral range with sub-nanometer wavelength accuracy. 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.