Safety Control for Prime Focus Spectrograph

Ting-Han Fan, Athindran Ramesh Kumar, Peter J. Ramadge

Abstract: Prime Focus Spectrograph is a telescope system to be deployed in Hawaii. The system consists of roughly 2400 controllable observation units, which we call the cobras, and the cobra control problem is to reach the targets while avoiding collisions. We decompose this problem into cobra assignment and trajectory planning. The cobra assignment adopts an efficient near-optimal algorithm that maximizes the target acquisition and completely avoids final-position collisions by losing only 0.9% of the target acquisition. The trajectory planning uses a collision-based search which lowers the in-transit collisions to almost zero.