An artificial star for in-situ telescope calibration

Star tracker telescopes are commonly used aboard space vehicles to provide attitude information, with the best reaching sub-arcsecond Pointing accuracy (<5 x 10-6 rad). The Gravity Probe B Relativity Mission (GP-B) is a satellite borne experiment that will use nearly perfect gyroscopes to measure the gravitational distortion of space-time predicted by Einstein's general theory of relativity. The GP-B telescope, which is the key angular reference for the relativity experiment, achieves revolutionary accuracy approaching 100 microarcsecond (0.5 x 10-9 rad).; The GP-B telescope needs a final end-to-end system test after integration into the satellite, and before launch. Testing to 50 milliarcsecond (240 x 10-9 rad) accuracy is sufficient, but the satellite assembly facility environment introduces jitter disturbances of 300 milliarcsecond (1.4 x 10-6 rad) and more into the system. Artificial Star 3 (AS3) is a novel solution to the requirement of calibrating a telescope to unprecedented precision after integration into a satellite. This is a particularly challenging task considering the exceptional precision required combined with the less than optimal environmental conditions, and the need for fast robust performance in the satellite assembly facility.; The portable, remotely operated, AS3 instrument mounts to the satellite, and projects a laser beam into the telescope within. An optical design for novel in-situ requirements was developed. On-line calibration systems, including a novel adaptation of a sliding aperture collimator, verify the beam geometry. Precision mechanisms enable beam scanning to an accuracy better than 30 milliarcsecond (0.15 x 10-6 rad); Fast automated test procedures were developed to acquire and reduce telescope science data on the fly. A simulator system was developed to enable testing and calibration before the time critical testing phase. An improved theoretical framework for determining telescope performance was developed, and was experimentally verified on flight hardware in a time critical NASA test sequence.; The fundamental novel achievement of this research is the first ever design, fabrication, and successful operation of a fast portable calibration system to test telescopes to accuracy approaching a milliarcsecond (5 x 10-9 rad), after the telescope has been integrated into the satellite system, and in the presence of disturbances.