Jeffrey J. Goldstein

Absolute wind velocities in the lower thermosphere of Venus using infrared heterodyne spectroscopy

Abstract Absolute wind velocities in the thermosphere of Venus were retrieved using NASA/Goddard Space Flight Center infrared heterodyne spectrometers at the NASA Infrared Telescope Facility (IRTF) and the McMath Solar Telescope, December 1985 to March 1987. Measurement of beam-integrated Doppler shifts in the nonthermal emission core of the 12C16O2 10.33-μm R(8) line provided sampling of the lower thermospheric wind field (100–120 km) projected along the line of sight. The spectrometers 1–2 arc-sec diffraction-limited beam yielded the spatial resolution necessary for circulation model discrimination. Saturated resonance (Lamb dip) stabilization of the reference CO2 laser local oscillator provided continuous absolute frequency calibration of the spectrometer to

Ethane abundance on Titan

Abstract Ethane (C2H6) abundance in Titans stratosphere is determined from recent ground based high spectral resolution measurements of individual ethane emission line spectra. Lines near 12 μm in the ν9 band of C2H6 were measured at a resolving power of λ/Δλ ∼ 106 with infrared heterodyne spectroscopy at the NASA Infrared Telescope Facility (IRTF). Globally averaged constant-with-height C2H6 mole fractions are retrieved for various possible thermal profiles on Titan. A range of possible stratospheric temperatures is investigated with respect to the data and a corresponding range of acceptable globally averaged ethane mole fractions is retrieved. The data and physical constraints imposed by the observations limit the temperatures in Titans upper stratosphere to 160–180 K. Corresponding acceptable mole fractions can range from 4 × 10−6 to 1.6 × 10−5 depending on the thermal profile used. For a currently “recommended” thermal profile a mole fraction of 9.4(−4.7, +9.4) × 10−6 is retrieved, some-what lower than previous results, but centrally placed in the acceptable temperature-abundance parameter space.