Space Interferometer Mission Testbed III (STB-3)

The Space Interferometer Mission Testbed III (STB-3) is part of the Space Interferometer Mission (SIM) project that is being developed at the Jet Propulsion Laboratory (JPL). SIM has various testbeds that will be used to demonstrate the feasibility of various technologies that should be demonstrated to mitigate risk to the SIM project and future Space Interferometer projects. Two major challenges are making precision measurements to picometer levels for the metrology system and controlling optical elements to nanometer levels. The STB-3 will be used to validate some of the nanometer technology that will be used by the SIM project. Specifically, STB-3 is designed to demonstrate pathlength feed-forward (PFF), white Light fringe acquisition and tracking under nanometer level pathlength control on a flexible structure. STB-3 will demonstrate pathlength feed-forward with a three-baseline interferometer on a flexible structure using a SIM like architecture. Pathlength feed-forward uses fringe position information from the two guide interferometers to properly adjust the delay line position of the science interferometer delay line. In addition, STB-3 will demonstrate disturbance rejection and attenuation, at the levels required by SIM. STB-3 will evolve into the SIM instrument testbed in four phases. Phase 1 will demonstrate PFF on optical tables, phase 2 will demonstrate PFF on a flexible structure, phase 3 will demonstrate "full interferometer" functionality on a flexible structure, and in phase 4 it will be upgraded to meet the flight interferometer integration and test, and operations needs. This paper focuses on phase one of STB-3, phase 1 goals, phase 1 description, the facility, and the phase 1 and 2 development strategy.