Method and experimental validation of a precision, reconfigurable pointing control strategy

We present a novel precision pointing strategy for application to spaceborne optical interferometers and laser intersatellite communication systems. The approach utilizes a six-axis active platform to reject disturbances from the noisy spacecraft bus to the precision payload over all frequencies: using 2 or 3 axis pointing at low frequency and 6 axis isolation at high frequency. The benefits of this strategy are: 1) the pointing function has a built in redundancy in case of actuator failure, 2) the active struts used for pointing can also be used to provide isolation or to augment an existing passive isolation system, and 3) broadband pointing stability does not require a high bandwidth pointing sensor. We focus on the pointing (low frequency) problem. The approach employs a decentralized controller through a decoupling transformation which converts desired rotations into corresponding strut lengths. The decoupling approach allows for simple SISO compensator design and for the incorporation of fault tolerant strategies