This article introduces the design and imaging principles of the Advanced Hyperspectral Imager (AHSI) aboard China's GaoFen-5 satellite. The AHSI is a visible and nearinfrared (VNIR)/short-wave infrared (SWIR) HSI. It is the first spaceborne hyperspectral sensor that utilizes both a convex-grating spectrophotometry and an improved three-concentric-mirror (Offner) configuration. It has 330 spectral bands, a 60-km swath width, and a 30-m spatial resolution. Various tests have been designed to evaluate its imaging performance, and the results indicate that the AHSI's performance is comparable to other spaceborne HSIs launched recently and those scheduled for launch in the next few years. The AHSI has the capability to detect and identify different ground objects.

The Advanced Hyperspectral Imager: Aboard China's GaoFen-5 Satellite

http://manuscript.elsevier.com/S0034425722000281/pdf/S0034425722000281.pdf

Using soil library hyperspectral reflectance and machine learning to predict soil organic carbon: Assessing potential of airborne and spaceborne optical soil sensing

The DLR Earth Sensing Imaging Spectrometer (DESIS) is a new space-based hyperspectral instrument developed by DLR and operated under collaboration between the German Aerospace Center (DLR) and Teledyne Brown Engineering (TBE). DESIS will be mounted on the International Space Station on the MUSES platform in 2018 and will provide hyperspectral Earth Observation in the wavelength range from visible to near-infrared with high resolution and near global coverage. TBE provides the platform and infrastructure on the ISS. DLR developed the instrument, while the optical system was fabricated and pre-aligned by the Fraunhofer Institut fur Angewandte Optik und Feinmechanik (IOF). This paper presents the on-ground adjustment, focusing and calibration approach for DESIS done at the optical lab of the Institut fur Optische Sensorsysteme (DLR). The optical lab set-up will be described in detail. Selected calibration results like detector Modulation Transfer Function (MTF) and linearity, optics MTF and wave front, focus position, smile and keystone measurement, instrument spatial and spectral MTF, and absolute radiometric calibration will be presented. The spectral and radiometric in- ight calibration approach of the DESIS calibration unit (CAL) based on stabilized Light Emitting Diode (LED) arrays will be demonstrated. In addition, the innovative pointing unit (POI) in front of the instrument and its pointing accuracy will be introduced. Finally imaging quality and accuracy of the sensor calibration will be evaluated with respect to foreseen applications.

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On-ground calibration of DESIS: DLR's Earth Sensing Imaging Spectrometer for the International Space Station (ISS)

The Sentinel-4 payload is a multi-spectral camera system, designed to monitor atmospheric conditions over Europe from a geostationary orbit. The German Aerospace Center, DLR Berlin, conducted the verification campaign of the Focal Plane Subsystem (FPS) during the second half of 2016. The FPS consists, of two Focal Plane Assemblies (FPAs), two Front End Electronics (FEEs), one Front End Support Electronic (FSE) and one Instrument Control Unit (ICU). The FPAs are designed for two spectral ranges: UV-VIS (305 nm - 500 nm) and NIR (750 nm - 775 nm). In this publication, we will present in detail the set-up of the verification campaign of the Sentinel-4 Qualification Model (QM). This set up will also be used for the upcoming Flight Model (FM) verification, planned for early 2018. The FPAs have to be operated at 215 K ± 5 K, making it necessary to exploit a thermal vacuum chamber (TVC) for the test accomplishment. The test campaign consists mainly of radiometric tests. This publication focuses on the challenge to remotely illuminate both Sentinel-4 detectors as well as a reference detector homogeneously over a distance of approximately 1 m from outside the TVC. Selected test analyses and results will be presented.

Verification of the Sentinel-4 focal plane subsystem

The DLR Earth Sensing Imaging Spectrometer (DESIS) is a new space-based hyperspectral sensor developed and operated by a collaboration between the German Aerospace Center (DLR) and Teledyne Brown Engineering (TBE). DESIS will provide hyperspectral data in the visible to near-infrared range with high resolution and near-global coverage. TBE provides the platform and infrastructure for the operation on the International Space Station (ISS), DLR has developed the instrument. This paper gives an overview of the design of the DESIS instrument together with results from the optical on-ground calibration. In-flight calibration, stability of dark signal and rolling vs. global shutter analysis will be presented.

DESIS - DLR earth sensing imaging spectrometer for the International Space Station ISS

The future ESA Earth Observation Sentinel-4/UVN is a high resolution spectrometer intended to fly on board a Meteosat Third Generation Sounder (MTG-S) platform, placed in a geostationary orbit. The main objective of this optical mission is to continuously monitor the air quality over Europe in near-real time. The Sentinel-4/UVN instrument operates in three wavelength bands: Ultraviolet (UV: 305-400 nm), Visible (VIS: 400- 500 nm) and Near-infrared (NIR: 750-775 nm). Two dedicated CCD detector have been developed to be used in the Focal Plane Subsystems (FPS), one for the combined UV and VIS band, the other covering the NIR band. Being a high resolution spectrometer with challenging radiometric accuracy requirements, both on spectral and spatial dimensions, an effect such the Random Telegraph Signal (RTS) can represent a relevant contribution for the complete system accuracy. In this work we analyze the RTS effect on data acquired during the FPS testing campaign with qualification models for the Sentinel-4/UVN detectors. This test campaign has been performed in late 2016. The strategy for the impact assessment of RTS is to measure the effect at room temperature and then to extrapolate the results to the at instrument operational temperature. This way, very-long lasting data acquisitions could be avoided since the RTS frequency is much lower at cryogenic temperatures. A reliable technique for RTS effect detection has been developed in order to characterize the signal levels amplitude and occurrence frequencies (flipping rate). We demonstrate the residual impact of the RTS on the global In-Orbit Sentinel-4/UVN instrument performance and products accuracy.

RTS effect detection in Sentinel-4 data

The DLR Earth Sensing Imaging Spectrometer (DESIS) is a new space-based hyperspectral sensor developed and operated by a collaboration between the German Aerospace Center (DLR) and Teledyne Brown Engineering (TBE). DESIS will provide hyperspectral data in the visible to near-infrared range with high resolution and near-global coverage. TBE provides the platform and infrastructure for the operation on the International Space Station (ISS), DLR is developing the instrument. This paper gives an overview of the design of the DESIS instrument together with first results from the optical calibration.

DESIS - DLR Earth Sensing Imaging Spectrometer

 The Sentinel-4 payload is a multi-spectral camera system which is designed to monitor atmospheric conditions over Europe The German Aerospace Center (DLR) in Berlin, Germany conducted the verification campaign of the Focal Plane Subsystem (FPS) on behalf of Airbus Defense and Space GmbH, Ottobrunn, Germany The FPS consists, inter alia, of two Focal Plane Assemblies (FPAs), one for the UV-VIS spectral range (305 nm … 500 nm), the second for NIR (750 nm … 775 nm) In this publication, we will present in detail the opto-mechanical laboratory set-up of the verification campaign of the Sentinel-4 Qualification Model (QM) which will also be used for the upcoming Flight Model (FM) verification The test campaign consists mainly of radiometric tests performed with an integrating sphere as homogenous light source The FPAs have mainly to be operated at 215 K ± 5 K, making it necessary to exploit a thermal vacuum chamber (TVC) for the test accomplishment This publication focuses on the challenge to remotely illuminate both Sentinel-4 detectors as well as a reference detector homogeneously over a distance of approximately 1 m from outside the TVC Furthermore selected test analyses and results will be presented, showing that the Sentinel-4 FPS meets specifications

/pdf/verification-of-the-sentinel-4-focal-plane-subsystem-273jlrcigz.pdf

Verification of the sentinel-4 focal plane subsystem

We expect commercial high resolution imaging systems, which are able to provide data with 25cm ground sample distance (GSD) or better in the near future. For selling the data, it is necessary to re-sample it to 30cm. The situation is similar when swinging out the satellite perpendicular to his ight direction. The GSD is then variable with the angle to Nadir direction. In this paper a method is proposed that the resolution adjusts adaptively according to the requirements.

Christian Williges

Papers

Verification of the Sentinel-4 focal plane subsystem

RTS effect detection in Sentinel-4 data

DESIS - DLR Earth Sensing Imaging Spectrometer

Verification of the sentinel-4 focal plane subsystem

Adaptation of spatial resolution for high resolution imaging system