User Interfaces of EnMAP

Kurzfassung

The objectives of the high-resolution imaging spectroscopy remote sensing mission EnMAP (Environmental Mapping and Analysis Program) are the investigations of a wide range of Earth surface parameters. The high-quality standardized products will be freely available to international scientific users for measuring and analyzing the status and evolution of various terrestrial and aquatic ecosystems. Therefore, it will cover the spectral range from 420 nm to 2450 nm with a spectral sampling distance varying between 4.8 nm and 12.0 nm. It will acquire 30 km in the across-track direction with a ground sampling distance of 30 m. The launch is scheduled for 2020 with an operational lifetime of 5 years. The EnMAP portal (www.enmap.org) is the central entry point for all users. It provides general mission information, e.g. on the space, ground, and science segment as well as related campaigns. Approximately 5,000 km in the along-track direction will be acquired per day, which are split to several observations. Therefore, the proposal handling and observation planning portal will be established to reasonably distribute the acquisition capacity to the user community. Registered users submit proposals based on Announcement of Opportunities placed by the science segment and mission management. Proposals specify especially the required coverage. If the proposal is accepted, the user plans the observations. The repeat cycle of 398 revolutions in 27 days has an orbit altitude of 652 km and combined with an across-track tilt capability of 30° this enables a target revisit time of less than 4 days. Each region is acquirable in the repeat cycle with an out-of-nadir angle of at most 5°. The local time of descending node is 11:00. Proposals, observations, and associated research will be presented by an interactive map supporting the establishment of a world-wide user network. In case of tasking conflicts, issued observations are prioritized especially based on historical and current cloud coverage information taking satellite constraints such as power and storage into account. All observations will be long-term archived. The catalog search and order service portal will allow all registered users to search and browse products based on the standardized protocols CSW (catalog service for the web) and WMS (web mapping service). Because of the necessary various processing options, each product will specifically be generated for each order and will be delivered using SFTP (secure file transfer protocol). The fully-automatic on-ground processing chain will generate calibrated hyperspectral image products at three levels for the users. Level 1A/1B products are corrected to Top-of-Atmosphere (TOA) radiances including, e.g., defective pixel flagging, non-linearity correction, dark signal (and digital offset) correction, gain matching, straylight correction, radiometric/spectral referencing, radiometric calibration, and spectral defective pixel interpolation (using a simplified pixel-based atmospheric correction). Level 1C products are orthorectified to a user selected map projection (UTM, geographic, or European projection LAEA) and resampling model (nearest neighbor, bi-linear interpolation, or cubic convolution). By the method of direct georeferencing, the physical sensor model, with a correction of sensor interior orientation, satellite motion, light aberration and refraction, and terrain related distortions from raw imagery is applied. Level 2A products are compensated for atmospheric effects to Bottom-of-Atmosphere (BOA) reflectances with separate algorithms for land and water applications. Therefore, a classification (e.g., land-water-background, cloud), aerosol optical thickness and also columnar water vapor estimation is performed to obtain surface or underwater reflectances including an adjacency correction. All processors are complemented by independent data quality control routines. Calibration equipment, especially a doped sphere with spectral features and a full aperture diffuser for Sun calibrations allows achieving a spectral accuracy of better than 1 nm as well as a radiometric accuracy of better than 5%. A geometric accuracy of 100 m is achieved - improved by on-ground processing to 30 m with respect to a used reference image. The offered operational services are complemented by a service team offering expert advice on the exploitation of EnMAP. In order to guarantee high consistency in particular all aspects of user interfaces are realized and operated by the Earth Observation Center (EOC) of the German Aerospace Center (DLR), which has long-lasting experiences with the airborne and spaceborne acquisition, processing, and analysis of hyperspectral data.