Share Email Print
cover

Proceedings Paper

Shear/defocus sensitivity of the mid-infrared channel (MIR) of the composite infrared spectometer (CIRS) for the Cassini mission to Saturn
Format Member Price Non-Member Price
PDF $14.40 $18.00

Paper Abstract

The Composite Infrared Spectrometer (CIRS) of the Cassini mission to Saturn has two interferometers covering the far infrared and mid infrared wavelength region. The mid infrared wavelength interferometer has a focal plane consisting of a germanium focus lens and HgCdTe array. System level calibration of the CIRS Flight Unit indicated a discrepancy between the expected and actual signal levels. Testing on the CIRS breadboard and Engineering Unit indicated that defocus of the germanium lens could significantly reduce the modulation efficiency of the interferometer in the presence of a moderate degree of wavefront shear. Defocus of the lens in the focal plane was of concern because of the temperature dependence of the index of refraction of germanium and the nominal operation temperature of 170 K. The shear/defocus interaction was extensively investigated and correlated to a newly developed analytical model. It was eventually determined that the CIRS instrument was in focus, had no appreciable wavefront shear and was operating near theoretical limits. The shear/defocus effect is however, of considerable interest, since it has not been described in previous literature on interferometers.

Paper Details

Date Published: 17 September 1998
PDF: 10 pages
Proc. SPIE 3435, Cryogenic Optical Systems and Instruments VIII, (17 September 1998); doi: 10.1117/12.323744
Show Author Affiliations
John G. Hagopian, NASA Goddard Space Flight Ctr. (United States)
Patricia A. Losch, NASA Goddard Space Flight Ctr. (United States)
Julie A. Crooke, NASA Goddard Space Flight Ctr. (United States)
Brent Mott, NASA Goddard Space Flight Ctr. (United States)
Anthony J. Martino, NASA Goddard Space Flight Ctr. (United States)


Published in SPIE Proceedings Vol. 3435:
Cryogenic Optical Systems and Instruments VIII
James B. Heaney; Lawrence G. Burriesci, Editor(s)

© SPIE. Terms of Use
Back to Top