The Estimation of Radiation Exposure for Arcsecond Pico Star Tracker (APST) in Low Earth Orbit

Abstract

In general COTS components have radiation tolerance of 1-10 Krad/year and untested components which are made up of silicon is estimated to have radiation tolerance up to 5 Krad. The primary idea of this paper is to estimate the Total Ionizing Dose (TID) of silicon and Single Event Upset (SEU) rates of the COTS components in LEO, using Space Environment Information System (SPENVIS) software. This analysis are performed for the orbital altitude of 400 to 600 km, inclination of 90° for one year. The result estimates that the target material silicon, without shielding acquired TID of 3.04 Mrad. The Aluminum shieling of 2mm and 3mm thickness reduces the TID to 3.04 Krad and 1.39 Krad respectively. The shielding of 2mm is optimum for COTS in LEO. At orbital inclination of 0°, 28° with a shielding of 2mm, the TID is 0.014Krad and 0.56 Krad respectively, but at 60° to 90° the TID increased to 3 Krad. The SEU rate varies for each device based on design, manufacturing technology, LET threshold, and maximum sensitive surface of the component. The results implies in worst case, bipolar, MOS, RAM device have error rate of 4.92 errors/bit-day, 10-1 errors/bit-day, 10-3 errors/bit-day respectively. The radiation testing procedures for TID are detailed