A study of TRMM static Earth sensor performance using on-orbit sensor data

This paper presents the results of a study of the Barnes static Earth sensor assembly (ESA) using onorbit data collected from the Tropical Rainfall Measuring Mission (TRMM) spacecraft. It is shown that there exist strong correlations between the large penetration angle residuals and the voltages produced by the Offset Radiation Source (ORS). The resultant roll pointing errors may lead to large drifts in the yaw angle between Digital Sun Sensor (DSS) observations, because the onboard propagation of the yaw angle does not take into account any errors in Earth pointing. This conclusion is further justified since observed drifts are found to be consistent with predictions by a simple roll-yaw coupling computation. Finally, the accuracy of the onboard algorithm used when only three of the four quadrants supply valid penetration angles is assessed. In terms of procedures used to perform this study, the analysis of ESA penetration angle residuals is discovered to be a very useful and insightful tool for assessing the health and functionality of the ESA.