Pointing-Stability Performance of the Cassini Spacecraft

摘要

The operations ofCassini optical remote sensing instruments require a high level of spacecraft-pointing stability tonminimize image distortion during an exposure window. This paper summarizes the flight performance of theCassininspacecraft’s pointing stability with respect to mission requirements. Sources of spacecraft jitter, the Cassininspacecraft control modes, and pointing-stability metrics are discussed to provide a context for the results. Inndesigning the Cassini attitude-control system, a pointing-stability performancemetric that considered the frequencyncontents of the disturbance sources was employed. Cassini pointing-stability results using the root-mean-squarenstability metric are provided for both spacecraft control modes, using the reaction-wheel assembly or the reactionncontrol system composed of eight thrusters. The pointing-stability results are then related to characteristics of thenspacecraft and operations. For thruster-based control, the pointing-stability results are analyzed with respect to thenper-axis dead band.Results fromthe scientific instruments onboard theCassini spacecraft confirmthat the pointing-nstability results in either controlmode have achieved high accuracy pointing capabilities critical to the success of thenmission and have resulted in data to improve our understanding of Saturn.