Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996dps....28.0320c&link_type=abstract
American Astronomical Society, DPS meeting #28, #03.20; Bulletin of the American Astronomical Society, Vol. 28, p.1068
Astronomy and Astrophysics
Astronomy
Scientific paper
We have performed a refined radiometric and wavelength calibration for selected spectra from the Mariner 7 Infrared Spectrometer (IRS) data set. Although the data are nearly 30 years old, they remain unique in the spectral coverage between 3 and 6 mu m. The longer wavelength data were acquired at a time when the atmosphere was relatively clear, in contrast to spectra obtained by the infrared spectrometer on board Mariner 9. In addition, the spectral resolution is significantly higher than that obtained by the Viking IRTM. We obtained a preliminary data set restoration from Martin (1985) that updates the observation geometry to the current martian coordinate system and provides a preliminary wavelength calibration. We have performed a radiometric calibration using pre-flight calibration targets provided with the data set and measured in flight observations of a space background following the basic method outlined by Hanel et al. (1992). We also performed a more accurate wavelength calibration using atmospheric absorptions observed in the calibrated data. The calibrated data are consistent in the spectral regions of overlap and probably accurate to around 10%. To date we have analyzed approximately 40 spectra for the complete wavelength range from 1.9 to 14.4 mu m, including regions of varying albedo, elevation and latitude. In particular, for the wavelength range from 8 to 14.4 mu m we note several absorptions attributed to CO_2 (also seen e.g. by Maguire, 1977) and a broad absorption from 8 to 12 mu m attributed to silicates. This latter absorption is primarily correlated to atmospheric pathlength and probably originates in atmospheric dust; however, variability in surface emissivity is also possible. We have also examined spectra near the edge of the seasonal south polar cap for evidence of water and CO_2 clouds. Spectra calibrated to brightness temperature and correlations with albedo and viewing geometry will be presented. Refs: Hanel et al., Exploration of the solar system by infrared remote sensing, p.259, 1992; Maguire W.C., Icarus, 32, p.85, 1977; Martin T.Z., Bull. Am. Astron. Soc., 17, p.723, 1985.
Calvin Wendy M.
Cimino G.
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