ABSTRACT
Infrared emission spectra recorded by airborne or satellite spectrometers can be searched for spectral features to determine the composition of rocks on planetary surfaces. Surface materials are identified by detections of characteristic spectral bands. We show how to define whether to accept an observed spectral feature as a detection when the target material is unknown. We also use remotely sensed spectra measured by the Thermal Emission Spectrometer (TES) and the Spatially Enhanced Broadband Array Spectrograph System to illustrate the importance of instrument parameters and surface properties on band detection limits and how the variation in signal-to-noise ratio with wavelength affects the bands that are most detectable for a given instrument. The spectrometer's sampling interval, spectral resolution, signal-to-noise ratio as a function of wavelength, and the sample's surface properties influence whether the instrument can detect a spectral feature exhibited by a material. As an example, in the 6-13-mum wavelength region, massive carbonates exhibit two bands: a very strong, broad feature at ~6.5 mum and a less intense, sharper band at ~11.25 mum. Although the 6.5-mum band is stronger and broader in laboratory-measured spectra, the 11.25-mum band will cause a more detectable feature in TES spectra.
ABSTRACT
We present a ratioing algorithm for quantitative analysis of the passive Fourier-transform infrared spectrum of a chemical plume. We show that the transmission of a near-field plume is given by τ(plume) = (L(obsd) - L(bb-plume))/(L(bkgd) - L(bb-plume)), where τ(plume) is the frequency-dependent transmission of the plume, L(obsd) is the spectral radiance of the scene that contains the plume, L(bkgd) is the spectral radiance of the same scene without the plume, and L(bb-plume) is the spectral radiance of a blackbody at the plume temperature. The algorithm simultaneously achieves background removal, elimination of the spectrometer internal signature, and quantification of the plume spectral transmission. It has applications to both real-time processing for plume visualization and quantitative measurements of plume column densities. The plume temperature (L(bb-plume)), which is not always precisely known, can have a profound effect on the quantitative interpretation of the algorithm and is discussed in detail. Finally, we provide an illustrative example of the use of the algorithm on a trichloroethylene and acetone plume.
ABSTRACT
The infrared spectrometer that recorded spectra of the atmosphere and surface of Mars during the Mariner 6 and 7 flyby missions is described. The instrument continuously scanned the 1.9-micro to 14.4-micro spectral region at 10 see per scan. Approximately 1% spectral resolution was furnished by two rotating, circular, variable interference filters. The spectral region 1.9-6.0 micro was recorded with a PbSe detector cooled to 175 K by radiation to deep space. The spectral region 3.9-14.4 micro was modulated by a cold (175 K) tuning fork chopper and recorded with a mercury-doped germanium detector cooled to 22 K by a Joule-Thomson two-stage (N(2) and H(2)) cryostat. The total weight of the instrument was 17.4 kg (monochromator plus electronics, 11.5 kg; gas delivery system, 5.9 kg), and it consumed 11 W of power.
ABSTRACT
The infrared spectra recorded by Mariner 6 and 7 show reflections at 4.3 microns. which suggest the presence of solid carbon dioxide in the upper atmosphere of Mars.
ABSTRACT
During the Mariner 7 flyby of Mars, the infrared spectrometer recorded distinct, sharp absorption. near 3020 and 3300 reciprocal centimeters between 61 degrees S and 80 degrees S. at the edge of the southern polar cap, with maximum optical density near 68 degrees S and 341 degrees E. These hands, which match in frequency the v(3) bands of methane and ammonia, can be associated with previously unreported spectral features of solid carbon dioxide exceeding 1 millimeter in thickness. Possible reasons for the geographic localization are discussed.
