Extremely Accurate Line of Sight Control between a Pointing and a Target Spacecraft

Extremely accurate Line Of Sight (LOS) control of a Pointing Spacecraft (S/C) with respect a Target S/C has been exploited in order to devise very advanced in-orbit scientific and technological experiments. The pointing performances are achieved by the utilisation of accurate sensors, low disturbance actuators and the development of a control scheme that takes advantage of state of the art technology. In this paper the simulation approach is presented, as well as the achieved results, when a relative alignment of two S/Cs nominally co-orbiting in GEO is required to be better than some milliarcseconds. Suitable dynamic and measurement models and control methods are developed and proved that the alignment can be obtained while oscillation jitters are maintained extremely low in the frequency band above a reference value of one Hz.