| Popis: |
NASA has built two airborne multi-spectral sensors to simulate space-borne instruments recently launched on the EOS (Earth Observing System) Terra satellite. The MODIS Airborne Simulator (MAS) and the MODIS/ASTER Simulator (MASTER) were designed to provide initial data sets to EOS investigators for algorithm development. MAS and MASTER are currently conducting calibration and validation under-flights for the MODIS and ASTER orbital instruments. These imaging spectrometers produce 50 spectral channels of 16-bit co-registered imagery data, from the blue wavelengths out though the thermal IR bands. Both systems share a common digitizer design developed originally for MAS. Greater accuracy and flexibility is achieved with high precision digital signal processors (DSPs) and field programmable gate arrays controlling the zero restoration, gain and antialiasing oversampling. Digitization rates of up to 100K samples per second per channel allow five-times oversampling at 6.25 scans per second and single sampling at 25 scans per second, resulting in aggregate data rates up to 2 Megabytes per second to disk. Both systems were designed for possible unattended operation on a NASA-ER2, but also support a realtime operator display for interactive mission evaluation on DOE’s B200 and NASA’s DC8. System design, characterization and performance will be covered by this paper. |
