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  • 1
    Publication Date: 2011-08-18
    Description: A method is developed for directly measuring atmospheric winds in the 20-120 km altitude interval from a spacecraft. The wind sensor measures the Doppler shift between the spectral absorption lines of a gas in a cell within the instrument and the thermal emission lines of the same gas in the atmosphere. The wind measurements are performed using a spacecraft-borne gas correlation spectrometer viewing the limb of the atmosphere. The wind-induced Doppler shift between the two spectra, and thus the magnitude of the wind itself, is obtained by phase modulating the incoming thermal radiation (equivalent to frequency modulation) by means of an electrooptically active crystal to determine the frequency shift required to reestablish exact correlation between the lines in the cell and the lines from the atmosphere. Results of numerical simulations of the wind-sensor performance indicate that the noise-equivalent-wind is between 1-5 m/s over most of the stratosphere and mesosphere.
    Keywords: GEOPHYSICS
    Type: Applied Optics (ISSN 0003-6935); 22; Sept. 1
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  • 2
    Publication Date: 2011-08-19
    Description: A passive infrared sensor for remote sounding of the wind field in the stratosphere and mesosphere from near earth orbital spacecraft is described. The sensor utilizes gas correlation spectroscopy and electrooptic phase-modulation techniques to measure winds in the 20-120 km altitude range, temperature, and atmospheric species concentrations. The operation of the sensor is examined. The sensitivity of the sensor is small Doppler shifts in an observed spectrum and the performance of the instrument were evaluated using laboratory simulation and numerical modeling. The data reveal that the sensor's wind measurements should have an accuracy better than 5 m/s and a spatial resolution of 5 km vertical by 150 km horizontal.
    Keywords: GEOPHYSICS
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  • 3
    Publication Date: 2017-10-02
    Description: With the release of Mars Odyssey Gamma Ray Spectrometer (GRS) results, which indicate the presence of vast reservoirs of near-surface ice in the martian polar regions, we are presented with an exquisite dilemma. These deposits, which are present as far down as 60 deg. latitude in both hemispheres, are consistent with the suggestion of thermal models that ice will be best protected in these extended regions during periods of higher obliquity. However, the current paradigm regarding the placement of these deposits, i.e., diffusive deposition of water vapor, appears to be inconsistent with the large volume mixing ratios (approx. 70%) inferred from the GRS data. This apparent conflict argues that diffusion alone cannot be the primary mechanism for the creation of these reservoirs, and that an alternate, large-scale process should be considered.
    Keywords: Astrophysics
    Type: Sixth International Conference on Mars; LPI-Contrib-1164
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