Metrology system for Space Interferometry Mission's system testbed 3

Abstract

The Space Interferometry mission's nano-meter class System Testbed has implemented an external metrology system to monitor changes in the length & orientation of the science interferometer baseline vector, which cannot be monitored directly. The output of the system is used in real time fringe tracking of dim stars. This paper describes the external metrology system, its mathematical representation, limitations, and method for estimating the length & orientation of the science baseline vector. Simulations and current system performance are presented and discussed.