The Environmental Mapping and Analysis Program HyperSpectral Imager (EnMAP HSI) will allow to acquire images of the Earth surface in a push-broom configuration. Spectral coverage includes 230 wavelength bands between 420 nm and 2450 nm, which are simultaneously recorded with a ground resolution of 30 m x 30 m.High requirements on the optical alignment of the Visual Near InfraRed (VNIR) and Short Wavelength InfraRed (SWIR) spectrometers and cameras have been fulfilled (one pixel lateral alignment and below 20 μm for defocus). In addition, a calibration and characterization campaign of the EnMAP HSI was performed, with the aim to verify the instrument requirements and to quantify its performance. The campaign addressed the following five responsivity domains: radiometric, polarization, spectral responsivity, spatial responsivity and stray light. A spectral calibration accuracy of 0.5 nm for VNIR and 1 nm for SWIR channel, and lateral calibration of the full field-of-view with sub-arc second accuracy was achieved. For all measurements, traceability to national standards is guaranteed by comparative measurements with calibrated devices.The paper presents the setups of the alignment, calibration and characterization measurements of the EnMAP HSI. Instrument requirements on calibration accuracy are reported. The traceability to national standards will be described and the validation of measurement accuracy.
The Environmental Mapping and Analysis Program (EnMAP) is a German space borne science mission that aims at characterizing the Earth's environment on a global scale. The single payload of the satellite is the Hyperspectral Imager (HSI). It is capable of measuring the solar radiance reflected from the Earth's surface as a continuous spectrum in the spectral range of 420nm to 2450nm, with a spectral sampling of 6.5nm (VNIR) and 10nm (SWIR). The EnMAP swath of 30km is sampled in spatial direction with 30m GSD.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.
Abstract. The high-resolution imaging spectroscopy remote sensing mission EnMAP (Environmental Mapping and Analysis Program, enmap.org) covers the spectral range from 420 nm to 2450 nm with a spectral sampling distance varying between 4.8 nm and 12.0 nm comprising 262 spectral bands. We focus on the planned framework concerning radiometry. The expected signal-to-noise ratio at reference radiance level is 500:1 at 495 nm and 150:1 at 2200 nm. The radiometric resolution is 14 bits and an absolute radiometric accuracy of better than 5% is achieved. Radiometric calibration is based on Sun calibration measurements with a fullaperture diffusor for absolute calibration. In addition, relative calibration monitors the instrument during the complete mission lifetime based on an integrating sphere (on the satellite). The fully-automatic on-ground image processing chain considers the derived radiometric calibration coefficients in the radiometric correction which is followed by the orthorectification and atmospheric compensation. Each of the two 2-dimensional detector arrays of the prism-based pushbroom dual-spectrometer works in a dual-gain configuration to cover the complete dynamic range. EnMAP will acquire 30 km in the across-track direction with a ground sampling distance of 30 m and the across-track tilt capability of 30° will enable a target revisit time of less than 4 days. The launch is scheduled for 2021. The high-quality products will be freely available to international scientific users for measuring and analysing diagnostic parameters which describe vital processes on the Earth’s surface.
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