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Proceedings Paper

Design of the infrared fast steering mirror chopping control system for the Keck II Telescope
Author(s): Jean-Noel Aubrun; Kenneth R. Lorell; Gregory J. Feher; Ernesto O. Perez; Paul J. Reshatoff; Donald F. Zacharie
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Paper Abstract

The Keck 2 ten meter telescope will utilize an advanced chopping secondary mirror in order to enhance observations in the infrared. The Infrared Fast Steering Mirror (IFSM) can execute a square-wave chop at frequencies as high as 25 Hz with an accuracy of +/- 0.1 arcsec. Chopping can be synchronized by focal plane instruments, and the system can simultaneously perform high-performance chopping as well as beam-steering (for atmospheric correction), providing the Keck telescope with greatly enhanced capability. Details of design, testing, and performance of the Keck 2 IFSM are presented in this paper. The mirror is controlled by three voice coil actuators. Reaction forces generated by the actuators are absorbed by a reaction mass suspended from the main IFSM structure. Motor driven springs are used to minimize power dissipation in the actuators. The IFSM all- digital control system uses a unique adaptive algorithm that forces the mirror to precisely follow the commanded chop waveform. Tests use various computerized instruments: a three-axis laser interferometer for calibration and stability, a 6-axis dynamometer to evaluate reaction forces transmitted to the telescope. In addition to specifics of the design, performance, and testing, a video illustrating details of the IFSM hardware and showing it in operation will be presented.

Paper Details

Date Published: 25 August 1998
PDF: 12 pages
Proc. SPIE 3352, Advanced Technology Optical/IR Telescopes VI, (25 August 1998); doi: 10.1117/12.319278
Show Author Affiliations
Jean-Noel Aubrun, Advanced Controls and Systems Development (United States)
Kenneth R. Lorell, Advanced Controls and Systems Development (United States)
Gregory J. Feher, Lockheed Martin Palo Alto Advanced Technology Ctr. (United States)
Ernesto O. Perez, Lockheed Martin Palo Alto Advanced Technology Ctr. (United States)
Paul J. Reshatoff, Lockheed Martin Palo Alto Advanced Technology Ctr. (United States)
Donald F. Zacharie, Lockheed Martin Palo Alto Advanced Technology Ctr. (United States)


Published in SPIE Proceedings Vol. 3352:
Advanced Technology Optical/IR Telescopes VI
Larry M. Stepp, Editor(s)

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