26 September 1989 Pointing Performance Analysis Of A Prototype Secondary Mirror Assembly For The Space Infrared Telescope Facility
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Abstract
The Space Infrared Telescope Facility (SIRTF), a NASA "Great Observatory" to be launched in the late 1990s, is a superfluid helium-cooled one meter class IR telescope with a sophisticated chopping facility provided by a dynamic two-axis tilt control capability of the secondary mirror. This paper describes the pointing performance analysis of the Prototype Secondary Mirror Assembly (PSMA) design. The two-axis PSMA tilt control system employs four linear actuators and four pairs of position eddy current sensors, and a reaction mass system to isolate the servo loops from the structural modes. The actuators and sensors operate in the 4 K environment of the secondary mirror assembly, while the control electronics reside in the "warm" electronics box outside the dewar. The PSMA design meets stringent pointing performance requirements over a range of discrete chop amplitudes and frequencies, for three different dynamic chop modes. The analysis of the pointing performance utilizes a detailed dynamic model of the PSMA in time and frequency domains, including the discretization and quantization effects in the servo-controllers, the sensor noise, and the structural modes. The servo stability issues are also addressed.
© (1989) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Sarma N. Gullapalli, Mark T. Stier, Michael A. Duffy, Richard A. Rockwell, Francis R. Sileo, Michael H. Krim, "Pointing Performance Analysis Of A Prototype Secondary Mirror Assembly For The Space Infrared Telescope Facility", Proc. SPIE 1111, Acquisition, Tracking, and Pointing III, (26 September 1989); doi: 10.1117/12.977969; https://doi.org/10.1117/12.977969
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