Abstract
Imaging spectrometry from aerial or spaceborne platforms, also known as hyperspectral remote sensing, provides dense sampled and fine structured spectral information for each image pixel, allowing the user to identify and characterize Earth surface materials such as minerals in rocks and soils, vegetation types and stress indicators, and water constituents. The recently launched DLR Earth Sensing Imaging Spectrometer (DESIS) installed on the International Space Station (ISS) closes the long-term gap of sparsely available spaceborne imaging spectrometry data and will be part of the upcoming fleet of such new instruments in orbit. DESIS measures in the spectral range from 400 and 1000 nm with a spectral sampling distance of 2.55 nm and a Full Width Half Maximum (FWHM) of about 3.5 nm. The ground sample distance is 30 m with 1024 pixels across track. In this article, a detailed review is given on the applicability of DESIS data based on the specifics of the instrument, the characteristics of the ISS orbit, and the methods applied to generate products. The various DESIS data products available for users are described with the focus on specific processing steps. The results of the data quality and product validation studies show that top-of-atmosphere radiance, geometrically corrected, and bottom-of-atmosphere reflectance products meet the mission requirements. The limitations of the DESIS data products are also subject to a critical examination.
Highlights
Airborne and spaceborne imaging spectrometers have advanced our understanding of the dynamic processes of ecosystems by enabling quantification of geochemical, biochemical and Sensors 2019, 19, 4471; doi:10.3390/s19204471 www.mdpi.com/journal/sensorsSensors 2019, 19, 4471 biophysical characteristics of the Earth through collection of contiguous spectra of the Earth’s surface over a defined wavelength range for each image pixel
Since the spectral shape of the differences between developed by the German Aerospace Center (DLR) Earth Sensing Imaging Spectrometer (DESIS) and RadCalNet are consistent over approximately six months, and as the overall magnitude of these differences is highly similar in relation to the RadCalNet uncertainty budget, it can be concluded that the DESIS radiometric calibration was stable over this period of time
Noisy bands should be removed from the hyperspectral image before the fusion process, in order to prevent the unmixing-based algorithm from selecting spurious endmembers: these have been identified as bands [1,2,3,4,5,6,7,8,9,10,11,137–148,226–235] for the DESIS scene above; in general, special care should be taken for any application involving spectral unmixing which uses the mentioned bands
Summary
Airborne and spaceborne imaging spectrometers have advanced our understanding of the dynamic processes of ecosystems by enabling quantification of geochemical, biochemical and Sensors 2019, 19, 4471; doi:10.3390/s19204471 www.mdpi.com/journal/sensors. Satellite (HySIS) (weblink available) and the Italian PRISMA mission [16], as well as future missions such as the German EnMAP [17], the Israeli SHALOM mission (REF) and ESA’s FLEX mission [18], which are technology demonstrators as well as science missions to prepare for more advanced spaceborne imaging spectrometers and suitable analysis techniques Another category includes large operational mapping missions such as the Copernicus Hyperspectral Imaging Mission for the Environment [19] and NASA’s. This article does not describe the design or specifications of the DESIS instrument and the MUSES platform, but rather the data products available to users and their quality as determined during the commissioning phase.
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