EnMap In-flight Calibration Status

The Environmental Mapping and Analysis Program (EnMAP) hyperspectral satellite mission was successfully launched on 1st April 2022. The mission aims to monitor and characterise Earth’s environment in the spectral range from 420 - 2450 nm. The VNIR sensor provides 91 science channels ranging from 420 - 1000 nm with an average Spectral Sampling Distance (SSD) of 6.5 nm. While the SWIR sensor covers the range from 900 - 2450 nm with 131 channels and 10nm SSD. - The off-nadir pointing capability (up to 30 degrees) enables 5000 km to be monitored per day, with a swath width of 30 km and a spatial resolution of 30 m. The EnMAP satellite is equipped with several subsystems which allow periodic in-flight monitoring and calibration. The Full Aperture solar Diffuser Assembly (FADA) is used for absolute radiometric calibration. The On-Board Calibration Assembly (OBCA) is composed of 2 integrating spheres: one is coated with a doped diffuser material and is used for the spectral calibration; the second sphere, coated with a white spectralon, is used for Radiometric stability monitoring. Linearity LEDs are placed in front of the detector to monitor their linearity by measuring the response at constant illumination with increasing integration times. The Shutter Calibration Mechanism (SCM) allows for measurements with no light input to be performed in order to compute Dark Signal values and, in combination with Deep Space measurements, to compute any existing shutter emission in the SWIR range. This contribution will present a summary of the calibration activities performed during the EnMAP Commissioning Phase

Une approche multi-disciplinaire pour la recherche de matière noire

Une grande partie de notre Univers consiste en un type de matière non-lumineuse intrinsèquement différente de tous les types de matière connus. Les preuves expérimentales suggèrent fortement que cette "Matière Noire" contribue à environ 80-85% de la matière de l'Univers. Ces dernières années, de nombreux résultats expérimentaux concernant la Matière Noire ont été publiés, faisant de ce domaine de recherche un des plus excitants. Beaucoup de données sont également attendues dans un avenir proche. Le but de cette thèse est d'établir le lien entre certains modèles de Matière Noire et leurs signatures expérimentales visibles dans les détecteurs actuels ou futurs. En ce qui concerne la détection indirecte de Matière Noire, une attention particulière est accordée à l'excès de électrons/positrons, qui peut en principe être expliqué par annihilations de Matière Noire dans notre Galaxie. Afin de tester cette possibilité nous effectuons une analyse "multi-messenger" combinant les contraintes de différents canaux astrophysiques tels que antiprotons, rayons gamma et signaux radio. Les incertitudes entrant dans le calcul des signatures de Matière Noire sont très importants et limitent notre capacité à extraire les respectives propriétés en cas de découverte. Par conséquent, évaluer et prévoir toutes les incertitudes pertinentes est essentielle, et une grande partie de cette thèse est consacrée à ce sujet. En particulier, nous étudions les perspectives pour la détermination de la propagation des rayons cosmiques avec AMS-02, les incertitudes systématiques sur la densité locale de Matière Noire et l'effet des incertitudes astrophysiques sur les expériences de détection directe.PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

A new German Hyperspectral Mission EnMAP: Image Products

The upcoming Environmental Mapping and Analysis Program (EnMAP) - German imaging spectroscopy mission - is a joint response of German Earth observation research institutions, value-added resellers and space industry to the increasing demand for accurate, quantitative information about the status and evolution of terrestrial ecosystems. EnMAP is currently in the construction phase with a launch planned in 2020. The project management is led by the Space Agency of DLR. The space segment consisting of instrument and bus will be established by OHB System AG. The EnMAP satellite will be operated on a sun-synchronous orbit at 643 km altitude with a local time of descending node 11:00 to observe any location on the globe under defined illumination conditions featuring a global revisit capability of 21 days under a quasi-nadir observation. The satellite has an across-track tilt capability of ± 30° enabling a revisit time of four days. The hyperspectral instrument will be realized as a pushbroom imaging spectrometer. Its data acquisition over the broad spectral range from 420 nm to 2450 nm will be performed by a CMOS (Complementary Metal Oxide Semiconductor) detector array for VNIR (visible and near infrared) with 95 spectral channels, i.e. 6.5 nm spectral resolution, and by a MCT (Mercury Cadmium Telluride) detector array for SWIR (shortwave infrared) with 135 spectral channels, i.e. 10 nm spectral resolution. The ground pixel size is 30 m × 30 m at nadir at 48° northern latitude. In this context a pointing accuracy of better than 500 m is expected. The pointing knowledge and therefore the accuracy of image products will be better than 100 m and can be improved by ground processing, if a reference image is available, to approximately 30 m (i.e. 1 pixel) w.r.t. the used reference image. The sensors’ 1000 pixels in spatial direction result in a swath width of 30 km. Regular on-board calibration measurements are performed to update the calibration tables for the processors. EnMAP level 0 (L0) image products (raw data) will be long-term archived while L1B products (systematically and radiometrically corrected data), L1C products (geometrically corrected data) and L2A products (atmospherically corrected data) will be processed on demand. The L1B processor corrects the hyperspectral image cube for systematic effects of the focal plane detector array, e.g. radiometric non-uniformities, and converts the system corrected data to physical at-sensor radiance values based on the currently valid calibration tables. The L1C processor creates ortho-images based on direct geo-referencing techniques implementing a line-of-sight model, which uses on-board measurements for orbit and attitude determinations as well as the sensor look direction vectors based on the currently valid calibration values. Furthermore, it is foreseen to automatically extract ground control points from existing reference data sets by image matching techniques to improve the geometric accuracy better than one pixel size. The L2A processor performs atmospheric correction and haze detection of the images by estimating the aerosol optical thickness and the columnar water vapor. Output products will be the ground reflectance cube and masks of land, water, cloud, cloud shadow, haze, cirrus and snow

Procedures for DataQC within the EnMAP and DESIS Ground Segments

Within this contribution, the procedures for ensuring the data quality within the ground segments of the hyperspectral DESIS and EnMAP missions are presented. In addition to the approaches for on-board calibration and instrument monitoring, the operational data quality control is included within the L0, L1B, L1C and L2A processors. Focus is set on the quality of the generated data products, including selected aspects of the radiometric and spectral scene properties, ortho-rectifcation and the atmospheric correction. Also selected aspects of an uncertainty estimation related to the radiometric and spectral properties and the L2A product are presented. Finally, the potential of the DESIS mission on board the ISS MUSES platform for improved site characterization and sensor cross-calibration (esp. with HISUI) is highlighted