Following work on the Wide-Angle Autonomous Star Sensor (WASS) reported at the 2nd GNC Conference the software has been extended to take into account specific types of radiation-induced CCD defect, i.e. single pixel proton blemishes, pixel (dark current & sensitivity) non-uniformity, and the degradation in charge transfer efficiency to be expectcd during die mission. The autonomous star identification method used is based on a 44 degree diameter sensor field of view and a reduced star catalogue of only 200 stars in which star triads are recognised by matching the star separations observed with a short separations catalogue (2000 entries). Work carried out on component asessment is capable of quantifying the defects induced by various levels of space radiation exposure but the type of modelling described in this paper is necessary to translate these findings into terms like successful star identification probability and rms angular pointing measurement noise and/or noisc spectral density which are more meaningful to the spacecraft systems engineer. A tool is also providcd for ,,software hardening' i.e. developing algorithms to recover, at least partially, sensor performance lost due to radiation-induced decfects. Results presented include dependence of whole sky identification probhability and of rms angular noise versus degree of radiation damage.
Further investigations into wide angle autonomous star sensing using the Monte Carlo method
1997
7 Seiten, 5 Bilder, 1 Tabelle, 2 Quellen
Conference paper
English
Further Evaluation of an Autonomous CCD Star Tracker by the Monte Carlo Method
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