Intracalibration of particle detectors on a three‐axis stabilized geostationary platform

Abstract

We describe an algorithm for intracalibration of measurements from plasma or energetic particle detectors on a three‐axis stabilized platform. Modeling and forecasting of Earth's radiation belt environment requires data from particle instruments, and these data depend on measurements which have an inherent calibration uncertainty. Pre‐launch calibration is typically performed, but on‐orbit changes in the instrument often necessitate adjustment of calibration parameters to mitigate the effect of these changes on the measurements. On‐orbit calibration practices for particle detectors aboard spin‐stabilized spacecraft are well established. Three‐axis stabilized platforms, however, pose unique challenges even when comparisons are being performed between multiple telescopes measuring the same energy ranges aboard the same satellite. This algorithm identifies time intervals when different telescopes are measuring particles with the same pitch angles. These measurements are used to compute scale factors which can be multiplied by the pre‐launch geometric factor to correct any changes. The approach is first tested using measurements from GOES‐13 MAGED particle detectors over a 5‐month time period in 2010. We find statistically significant variations which are generally on the order of 5% or less. These results do not appear to be dependent on Poisson statistics nor upon whether a dead time correction was performed. When applied to data from a 5‐month interval in 2011, one telescope shows a 10% shift from the 2010 scale factors. This technique has potential for operational use to help maintain relative calibration between multiple telescopes aboard a single satellite. It should also be extensible to inter‐calibration between multiple satellites.