Upgrade of the MAGIC Telescope with a Multiplexed Fiber-Optic 2 GSamples/s FADC Data Acquisition system

In February 2007 the MAGIC Air Cherenkov Telescope for gamma ray astronomy was fully upgraded with a fast 2 GSamples/s digitization system. The upgraded readout system uses a novel fiber-optic multiplexing technique. It consists of 10-bit 2 GSamples/s FADCs to digitize 16 channels consecutively and optical fibers to delay the analog signals. A distributed data acquisition system using GBit Ethernet and FiberChannel technology allows to read out the 100 kByte events with a continuous rate of up to 1 kHz.Comment: 4 pages, 6 figures, to appear in the proceedings of the 30th International Cosmic Ray Conference, Merida, July 200

Specific data correction for EnMAP and DESIS

The processing chains of the upcoming hyperspectral missions DESIS (DLR Earth Sensing Imaging Spectrometer), and EnMAP (Environmental Mapping and Analysis Program) need to deal with several systematic errors. This work will present some of the existing problems and the selected correction and attenuation procedures. One common error is the smile effect, affecting push-broom hyperspectral sensors by shifting the central wavelength in the across-track direction. This spectral distortion is minimal in the center of the sensor, increasing towards the sensor edges. The smile effect is particularly noticeable on hyperspectral sensors as the band width is in the order of a few nanometers. EnMAP performs a column-wise smile-aware atmospheric correction, taking the shifted wavelengths into account and interpolating the BOA (Bottom Of Atmosphere) reflectances to the sensor's nominal wavelengths. On the other hand, DESIS addresses the smile correction interpolating TOA (Top Of Atmosphre) radiances. An even more common data error, not only to DESIS and EnMAP but to every type of imaging system, is the existence of abnormal or defective pixels. These abnormal pixels can be present due to sensor aging, errors during data acquisitions, saturation of the sensor, etc. EnMAP strategy for abnormal pixel is based on linear interpolations of the BOA reflectances in the spectral direction. In the case of DESIS, a hybrid interpolation method for abnormal pixels is used. The algorithm selects the optimum value between spectral and spatial cubic spline interpolations of the TOA radiances. The selection criterion is based on the spectral gradient difference between the interpolated pixels and spatial neighbors. Finally this work will present a DESIS specific effect which is introduced, during the data acquisition, by the imaging sensor’s shutter mode. The rolling shutter mode provides higher frame rate and better SNR (Signal to Noise Ratio) than global shutter. As a negative side effect, every individual band from any specific row in the along-track direction is acquired at slightly different time, and therefore, at slightly different position on the ground. To correct this effect, the speed of the ISS (International Space Station) and the band acquisition times are used in order to calculate the point to be interpolated via a cubic spline interpolation in the along-track direction

The EnMAP Ground Segment user services and products

EnMAP (Environmental Mapping and Analysis Program) is a high-resolution imaging spectroscopy remote sensing mission dedicated to monitor and characterizing Earth's environment by providing accurate information on the state and evolution of terrestrial and aquatic ecosystems. EnMAP is equipped with a prism-based dual-spectrometer, which can make observations in the spectral range between 418.2 nm and 2445.5 nm with 224 bands and a high radiometric and spectral accuracy and stability. The EnMAP satellite was launched on 1 April 2022 and completed its commissioning phase in November 2022. From March 2023 EnMAP accepts user requests to acquire new acquisitions or download products from the mission archive. The EnMAP Ground Segment, under the responsibility of the German Aerospace Center (DLR), provides the services necessary to command the satellite and receive, archive and process the EnMAP data up to the three user product levels that can be ordered. These products are the radiometrically corrected at sensor top-of-the-atmosphere radiance product (L1B), the radiometrically corrected and orthorectified top-of-the-atmosphere radiance product (L1C) and the atmospherically corrected bottom-of-the-atmosphere reflectance product (L2A). The L2A processing supports options for Land processing, Water processing and a combine mode that automatically selects the correction based on pixel classification. In this contribution we offer an overview of the services provided by the EnMAP Ground Segment to the EnMAP data users: planning of new EnMAP acquisitions, access to archived data products and data processing. We cover in particular those aspects that, according to the user feedback, have been more challenging for the EnMAP users. We also provide an overview of the EnMAP products available and the different access or processing options that users can choose from