Experience and results of long-term in-orbit sun calibration of the Modular Optoelectronic Scanner (MOS) on the Indian IRS-P3 mission

摘要

The Modular Optoelectronic Scanner MOS was developed at the Institute of Space Sensor Technology/Berlin of the German Aerospace Center (DLR) and specially designed for observations of medium scale effects of the system surface-atmosphere. MOS consists of the two VIS/NIR imaging spectrometers MOS-A and MOS-B and the SWIR camera MOS-C. It was launched on March 21, 1996 on board the Indian Remote Sensing Satellite IRS-P3 together with the Indian Wide Field Scanner WIFS and an X-ray instrument. Two different in-orbit calibration devices are integrated into the MOS equipment: (1) the internal calibration system based on two minilamps and (2) the sun calibration based on spectralon diffusers for absolute radiometric recalibration and long-term stability check of the sensitivity. Thus it is possible to determine the actual relative calibration data with an accuracy of about 0.5%. The interpretation of the calibration data of the MOS-IRS mission in orbit for two years shows that all detector elements really are working normally. The behavior of the sensitivity of all elements of a CCD-line is nearly identical. Altogether, the sensitivity of the MOS-A channels remains constant in an interval of plus or minus 0.7%, increases by different amounts for the MOS-B channels up to 6% and decreases for MOS-C about 1%. The results of the in-orbit calibrations are the basis for a consistent interpretation of the remote sensing measurements of the environment.