Compact Imaging Spectrometers using Acousto-Optic Tunable Filters

We describe planetary science observations made with the Goddard Space Flight Center, acousto-optic tunable filter (AOTF) cameras. This technology is a newly developed RF-tunable spectrophotometric imager. We describe four generations of AOTF camera designed, fabricated and demonstrated by the GSFC AOTF Camera Team over the decade of the 1990’s. At each step making incremental steps toward the long-wavelength limit of the tellurium dioxide (TeO2) AOTF cell material. TeO2 is the most mature AOTF material and the best choice for operation at wavelengths in the 0.4-5.1 mm region. Because of several unique aspects of AOTF cameras, we briefly describe this technology in the introductory section. In Section 2 we describe our first camera which employed a Si CCD array. Adaptive optics observations of Jupiter and Saturn were made using this camera. Section 3 describes three versions of near-IR camera. It opens with a discussion of Venus observations made with our first near-IR camera employing Rockwell HgCdTe array technology. This camera had a 3.0-mm cutoff wavelength. Mars and Saturn were recently observed with our 3.8-mm camera. Our newest camera which we are completing this summer (2000) will extend the spectral range over 2.5-5.2 mm. We will discuss the new array performance and provide preliminary interpretations of some of these results.