PLANCK AOCS: PRECISE ON-BOARD CONTROL FOR SLOWLY SPINNING SC

摘要

Planck is an ESA scientific mission for investigation of the Cosmic Microwave Background distribution. The mission will perform a full map of this radiation in the celestial sphere for which purpose the satellite will continuously spin. Frequent and small reorientations of the spin direction and the corresponding swapping belt observed in every spin will be performed. The Planck Spacecraft has been developed and will be launched together with Herschel by Ariane 5, and both satellites will be injected in two different orbits around the Second Sun-Earth Lagrangian point(L2). A general but systematic view of the design for the AOCS and the properties that this design introduces is described in this paper. In particular the implications of the spinning nature of the mission, the small angular velocity, the high level of autonomy and the frequency of attitude manoeuvres are described. All these aspects have driven a quite special AOCS design, which combines the spinning satellite control methods, with the autonomous on-board attitude determination and control, producing a quite non-conventional control concept compared with both conventional 3-axis satellites and spinning satellites. In this paper emphasis will be made on the AOCS constrains, the design considerations, the derived design, and the obtained results. Major properties of the AOCS include the innovative usage of the same star sensor for a 3-axis and a slowly spinning satellite (via Time Delay Integration[TDI] technique), the fully autonomous on-board attitude determination and control, the autonomous on board selection and distribution of thrusters for the Orbit Control, and the high level of safety included on-board. Finally some results and conclusions obtained during the project will be presented.