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A model for the vertical sound speed and absorption profiles in Titan's atmosphere based on Cassini-Huygens data

Journal of the Acoustical Society of America, ISSN: 0001-4966, Vol: 131, Issue: 5, Page: 3671-3679
2012
  • 17
    Citations
  • 0
    Usage
  • 11
    Captures
  • 0
    Mentions
  • 0
    Social Media
Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    17
    • Citation Indexes
      17
  • Captures
    11

Article Description

Measurements of thermodynamic quantities in Titan's atmosphere during the descent of Huygens in 2005 are used to predict the vertical profiles for the speed and intrinsic attenuation (or absorption) of sound. The calculations are done using one author's previous model modified to accommodate non-ideal equations of state. The vertical temperature profile places the tropopause about 40 km above the surface. In the model, a binary nitrogen-methane composition is assumed for Titan's atmosphere, quantified by the methane fraction measured by the gas chromatograph/mass spectrometer (GCMS) onboard Huygens. To more accurately constrain the acoustic wave number, the variation of thermophysical properties (specific heats, viscosity, and thermal conductivity) with altitude is included via data extracted from the NIST Chemistry WebBook [URL webbook.nist.gov, National Institute of Standards and Technology Chemistry WebBook (Last accessed 10/20/2011)]. The predicted speed of sound profile fits well inside the spread of the data recorded by Huygens' active acoustic sensor. In the N-dominated atmosphere, the sound waves have negligible relaxational dispersion and mostly classical (thermo-viscous) absorption. The cold and dense environment of Titan can sustain acoustic waves over large distances with relatively small transmission losses, as evidenced by the small absorption. A ray-tracing program is used to assess the bounds imposed by the zonal wind - measured by the Doppler Wind Experiment on Huygens - on long-range propagation.

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