Space-Based Visible Metric Accuracy

Abstract

In April 1996 theMidcourse SpaceExperiment satellite, sponsoredby theBallisticMissile Defense Organization, was launched into an 898-km altitude, nearly sun-synchronous orbit. One of the principal sensors onboard the spacecraft is the Space-Based Visible, a visible-band electrooptical camera used for space surveillance. The instrument is equipped with four adjacent 420 £ 420 pixel charge-couple devices and was designed with high off-axis stray light rejection characteristics for observing near the earthlimb. As the Ž rst space-based space surveillance sensor, the Space-Based Visible’s principal role is to gather metric and photometric information on a wide variety of resident space objects. To assess the metric performance of the sensor, routine on-orbit metric calibration is performed. In addition, a complete error assessment was made using actual  ight data. The goal of producing 4-arc-s (1-sigma) observations of resident space objects was set during design, and early results show that this goal is being reached. The analysis of each of the error sources within the Space-Based Visible error budget is presented and results from both calibration and routine surveillance data collection events are shown. Error sources such as those associated with the sensor boresight pointing, including star catalog errors, spacecraft jitter, star centroiding, and optical distortion, along with the Midcourse Space Experiment ephemeris and the streak endpoint determination are discussed. The principal Ž nding, as revealed through the discrepency between the theoretical error assessment and on-orbitmetric calibration, spawned the identiŽ cation of an unmodeledmetric error source for the Space-Based Visible. With the identiŽ cation and modeling of this error source, a 50% reduction in the metric error budget of the sensor is possible.