Optical chopper for the HIRDLS instrument

Walter G. Opyd; Wayne Rudolf; Stuart Loewenthal; Thomas Heal Jr.

doi:10.1117/12.331315

18 November 1998 Optical chopper for the HIRDLS instrument

Walter G. Opyd, Wayne Rudolf, Stuart Loewenthal, Thomas Heal Jr.

Proceedings Volume 3437, Infrared Spaceborne Remote Sensing VI; (1998) https://doi.org/10.1117/12.331315
Event: SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, 1998, San Diego, CA, United States

Abstract

Test chipper performance, as well as mechanical design and electronic control concepts, are presented for the optical chopper developed for the High-Resolution Dynamics Limb Sounder (HIRDLS) to be flown on the CHEM-1 satellite of the NASA Earth Observing System (EOS). Optical chopping is essential in order to achieve the required sensitivity and accuracy in measurement of infrared emission from various chemical species in the earth's atmosphere. Chopping of the optical input as far forward in the telescope as practical minimizes calibration errors arising from variations in emission from warm optics and due to electronic drifts in the infrared detecting system. At 500 Hz, the reflective chopper blade switches between the atmospheric limb view and reference radiation from cold space. The HIRDLS chopper is a six- toothed, mirrored wheel driven by a three-phase, permanent- magnet, brushless DC motor with trapezoidal excitation synchronized to motor back-emf. Chopper design was driven by requirements of (1) continuous operation at 5000 RPM for 50,000 hours in space vacuum, (2) chopping amplitude stability of one part in 100,000, (3) lubricant loss control for both bearing reliability and prevention of optics contamination, (4) compact size to fit in the folded telescope, and (5) survival in the launch environment.

Citation Download Citation

Walter G. Opyd, Wayne Rudolf, Stuart Loewenthal, and Thomas Heal Jr. "Optical chopper for the HIRDLS instrument", Proc. SPIE 3437, Infrared Spaceborne Remote Sensing VI, (18 November 1998); https://doi.org/10.1117/12.331315

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