[Show abstract][Hide abstract] ABSTRACT: In March 1979, the spectrum of Venus was recorded in the far infrared from the G.P. Kuiper Airborne Observatory when the planet subtended a phase angle of 62°. The brightness temperature was observed to be 275°K near 110 cm−1, dropping to 230°K near 270 cm−1. Radiance calculations, using temperature and cloud structure formation from the Pioneer Venus mission and including gaseous absorption by the collision-induced dipole of CO2, yield results consistently brighter than the observations. Supplementing the spectral data, Pioneer Venus OIR data at similar phase angles provide the constraint that any additional infrared opacity must be contained in the upper cloud, H2SO4 to the Pioneer-measured upper cloud structure serves to reconcile the model spectrum and the observations, but cloud microphysics strongly indicates that such a high particle density haze is implausible. The atmospheric environment is reviewed with regard to the far infrared opacity and possible particle distribution modifications are discussed. We conclude that the most likely possibility for supplementing the far-infrared opacity is a population of large particles in the upper cloud with number densities less than 1 particle cm−3 which has remained undetected by in situ measurements.
[Show abstract][Hide abstract] ABSTRACT: A spectrum of the disk of Jupiter was obtained in January 1978 from the Kuiper Airborne Observatory, covering the 100- to 300-cm−1 spectral range at a resolution corresponding to 1.65 cm−1. Although taken more than a year before the Voyager 1 Jupiter encounter, this spectrum serves to extend the Voyager IRIS experiment coverage down from its lower limit of 200 cm−1. Analysis of the spectrum provides information on global mean properties of ammonia gas and an ammonia ice haze. A vertical distribution indistinguishable from saturation equilibrium, with a sharp depletion near the temperature minimum, matches the observed shape of the rotational line absorption best. Constraints on the total optical thickness of the ammonia ice haze can be made, but other properties, such as particle size or vertical scale height, cannot be distinguished clearly from our data in this spectral region. Nevertheless, all models of the haze produce a “continuum” thermal emission between the NH3 line manifolds which is much lower than that produced by the H2 collision-induced dipole opacity.
[Show abstract][Hide abstract] ABSTRACT: The spectrum of Venus was measured between approximately 500 and 800 cm−1 (12 to 20 μm) at a resolution of 3.12 cm−1 from the NASA C141 G.P. Kuiper Airborne Observatory on 22 and 24 February 1977. The spectrum clearly shows the detailed structure of CO2 absorption in the vicinity of the ν2 fundamental band at 667 cm−1. In addition, details of model fitting demonstrate the possibility for a cold and thin haze of sulfuric acid droplets along with an optically opaque cloud top near 250°K. Such clouds represent major differences from other H2SO4 main cloud deck models in the recent literature and may be indicative of changes in the vertical distribution of aerosols on a global scale. A retrieval of the temperature structure was obtained for a limited vertical region (0.63 to 1.6 mbar). The temperatures retrieved for pressures at or below 10 mbar are largely independent of the cloud model assumed and they are some 16 to 20°K warmer than the 1972 NASA model. All retrieved temperatures lie within the range of Mariner 5 and Mariner 10 radio occultation inversion results.
[Show abstract][Hide abstract] ABSTRACT: The Q and R branches of the C2H2 ν5 fundamental, observed in emission in an aircraft spectrum of Jupiter near 750 cm−1, have been analyzed with the help of an improved line listing for this band. The line parameters have been certified in the laboratory with the same interferometer used in the Jovian observations. The maximum mixing ratio of C2H2 is found to be between 5 × 10−8 and 6 × 10−9, depending on the form of its vertical distribution and the temperature structure assumed for the lower stratosphere. Most consistent with observations of both Q and R branches are: (1) distributions of C2H2 with a constant mixing ratio in the stratosphere and a cutoff at a total pressure of 100 mbar or less, and (2) the assumption of a temperature at 10−2 bar which is near 155°K.
[Show abstract][Hide abstract] ABSTRACT: Spectroscopic measurements of the thermal radiation from Jupiter between 12 and 24 micrometers (420 to 840 reciprocal centimeters) with a resolution of 4 reciprocal centimeters are used to infer the Jovian temperature structure in the pressure region 0.1 to 0.4 atmosphere. The brightness temperature spectrum is in good agreement with previous ground-based measurements between 11 and 13 micrometers and with airborne measurements between 18 and 25 micrometers. However, the integrated flux calculated for a filter window and viewing angle equivalent to those of the 20 micrometer channel of Pioneer 10 is 20 percent below that measured by the Pioneer infrared radiometer. The Q branch of the v(5) fundamental band of acetylene at 730 reciprocal centimeters appears in emission and leads to a mixing ratio estimate of 10(-6 +/- 0.5).