A HIGH-ORDER KALMAN FILTER FOR FOCAL PLANE CALIBRATION OF NASA’s SPACE INFRARED TELESCOPE FACILITY (SIRTF)

This paper discusses the Instrument Pointing Frame (IPF) Kalman Filter, which is an algorithm developed for focal plane calibration of NASA’s Space Infrared Telescope Facility (SIRTF). The IPF Kalman filter is a high-order square-root iterated linearized Kalman filter which is parametrized specifically for calibrating the telescope focal plane and aligning the science instrument arrays with respect to the telescope boresight. The most stringent calibration requirement specifies an alignment accuracy of 0.14 arcseconds, 1-sigma, radial. In order to achieve this level of accuracy, the filter carries 37 states to estimate desired frames while also correcting for systematic errors in pointing. The estimated pointing frames and calibration parameters are essential for precision telescope pointing, and end-to-end “pixels on the sky” ground pointing reconstruction.