Space Interferometry Mission instrument model and astrometric performance validation

• Published in: IEEE transactions on aerospace and electronic systems Vol. 40; no. 4; pp. 1228 - 1238
• Main Authors: Basdogan, I., Milman, M.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-10-2004; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Delay lines; Dynamical systems; Error analysis; Extraterrestrial measurements; Feeds; Instruments; Interferometers; Mathematical models; Metrology; Missions; Optical feedback; Optical interferometry; Optical sensors; Position measurement; Science; SIM; Space missions; Stars
• ISSN: 0018-9251; 1557-9603
• DOI: 10.1109/TAES.2004.1386876

The Space Interferometry Mission (SIM), performed very accurate astrometric measurements to measure the positions of stars using a 10 m baseline optical interferometer. The lack of signal from the science targets precludes using the star as a feedback signal to control the science interferometer delay line. In order to solve this problem SIM uses pathlength feed forward (PFF) control of the science interferometer. In the case of controlling the science interferometer optical path, the information to position the science delay line comes from a combination of internal metrology, external metrology, and guide interferometer measurements. The accuracy of the internal and external metrology measurements and the guide interferometer measurements are important for the quality of the feed forward signal and also for the ultimate astrometric performance of the instrument. An instrument model of SIM has been built to evaluate optical performance and to emulate various observational scenarios. The effect of averaging methods to reduce metrology cyclic error and the viability of on-orbit calibration maneuvers are studied. The model consists of a real-time dynamics formulation of the spacecraft and a real-time attitude control system. Simulation results investigate the sensitivity of the feed forward signal to the various error sources and time-varying terms.