An observational program was designed for systematic spatial and temporal monitoring of the Jovian atmosphere at several wavelengths chosen for their different absorptive properties. The weak broadband (5Å/pixel) CH₄ absorptions (6190 and 7270Å) probe the deep (2-4 bars) cloud layer while the stronger band at 8900Å probes the upper 400-600 mbars. The high resolution (~50mÅ/pixel) 3-0 H₂ quadrupole wavelengths probe to about 1-2 bars. The gradual increase in the measured equivalent widths of the H₂ quadrupole lines from the east to west limb is most likely indicative of a diurnal change in the vertical cloud structure. Such a variation is consistent with the properties of a convective layer driven by internal heat, with solar heat deposited at the top. The CH₄ data from the same time period was modelled for the south tropical zone. Since these absorptions are sensitive to several atmospheric layers it is difficult to separate the effects of the various cloud parameters on the [(I/F)(band)]/[(I/F)(cont)] values. There are no obvious limb to limb variations in these bands but several cloud parameters may be changing simultaneously, introducing compensating affects on the [(I/F)(band)]/[(I/F)(cont)] values. The two limbs may not, therefore, appear significantly different even if they are representative of substantially different cloud structures. The June 1983 H₂ data has been modelled at seven different latitudes and cloud structure differences are indicated. The average models representing the belt regions require somewhat thinner optical depths for the upper ammonia cloud (τ(cl) = 3-4.5) than the zones (τ(cl) = 5.5-6.5) or the equatorial region (τ(cl) = 6.5-7). These data also provide some constraints on the thermodynamic state of the hydrogen. A model atmosphere with only "normal" hydrogen (ortho-H₂ to para-H₂ of 3:1) is not able to fit both of the 3-0 lines simultaneously. Model atmospheres with all of the hydrogen in a state of equilibrium fit the two lines much better. Models with small amounts of disequilibrium hydrogen in the upper atmosphere also provide reasonable average fits to our H₂ data and cannot be easily distinguished from those that incorporate only equilibrium hydrogen at all levels or from those which incorporate "normal" in the top 300 mbars of the Jovian atmosphere.

No description available.

Pioneer 10 and 11 polarimetry maps of Jupiter, taken at a wide variety of phase angles, have been analyzed. Data were reduced in two colors for Jupiter's South Equatorial Belt (latitude -5 to -8 degrees) and scattering models were constructed. Variations in polarization from center to limb set constraints on the vertical structure of the atmosphere. The absolute polarization near the center of the disc constrained the single scattering polarization phase matrix of the scattering particles. After exploring several types of cloud models, it was found that a two cloud model with a haze in the upper atmosphere fits the data best. Several types of vertical structures were ruled out, including gas over a nonpolarizing Lambert surface, gas over a polarizing cloud deck, uniformly mixed gas with scattering particles (Reflecting Scattering Model), and models where the cloud tops diffusely mixed with gas as a function of altitude. Constraints have been set upon the polarimetric scattering properties of the haze and lower clouds. The haze particles are closely approximated by conservatively scattering spheres of index of refraction 1.5 and uniformly distributed sizes between 0.16 and 0.18 microns radius. A relationship exists between the required index of refraction for the haze particles and the mean size of the particles. It is possible that the particles are more broadly distributed in size, as this area was not extensively explored. The optical depth of the haze is between 0.125 and 0.250 at a wavelength of 0.44 microns, and lies near the 200 millibar pressure level. The upper cloud, which is thought to be made of ammonia crystals, must be at least optical depth 2, and could be semi-infinite. The polarization scattering properties of the clouds are distinctly different from the haze, indicating a compositional or size difference. The cloud particles have polarizing properties indicative of large (larger than 0.5 micron radius) particles. The upper cloud has been modelled to be near the 500 millibar level, but the pressure level for the best fitting model depends upon the chosen single scattering phase matrix. For more negatively polarizing cloud particles, the cloud would be located deeper in the atmosphere. The lowest cloud is more weakly constrained. Its scattering properties are set the same as the upper cloud, and it has been modelled as having semi-infinite optical depth. For the nominal scattering phase matrix, this cloud is located near the 2250 millibar pressure level. The constraints set on both the vertical structure and the particle scattering properties can be useful in the determination of Jupiter's solar flux deposition profile. Additionally, the location of the cloud and haze layers in Jupiter's atmosphere is important to the understanding of the heat balance of the planet, as well as to the understanding of the global dynamic of Jupiter's atmosphere.

Researchers analyzing the upper clouds of Jupiter and Saturn are unable to theoretically reproduce the data returned by Pioneers 10 and 11 and Voyagers 1 and 2 with an approach based on Mie theory. Ammonia crystals are believed to be an important constituent of Jupiter's upper clouds, but both their shape and scattering properties were unknown at the start of this work. Ammonia crystals and water crystals were grown in a cold chamber at temperatures 20°C below their freezing points (0°C and -77.7°C, respectively). The H₂O crystals formed had shapes in agreement with published growth habit diagrams. The NH₃ crystals formed were usually irregular in shape, but regular four-sided pyramids were commonly observed. This four-sided pyramidal shape is in agreement with ammonia's primitive cubic crystal structure. Ammonia crystals could not be formed at temperatures above -95°C due to nucleation problems. A scattering measuring instrument was constructed with fifteen separate lens-detector combinations aimed at a common point in the center of the cold chamber. A laser beam (6328Å wavelength) traversed the chamber center, illuminating any crystal aerosal clouds present. A computer was used to rapidly sample the outputs of the fifteen detectors and to drive a photoelectric modulator to change the slow speed polarization properties of the laser beam. The measurements resulted in a determination of the single scattering phase function and degree of linear polarization for the crystal species present. Water crystals were found to have scattering properties similar to that reported by previous researchers. The H₂O crystal scattering possesses a smaller backscatter peak and smaller polarization features than is common for water spheres of similar size. A negative polarization of 5% occurred in the forward scattering hemisphere and a positive polarization of 10% in the rear. Ammonia particles were observed to have a backscattering peak four times higher than for water crystals. The NH₃ particle light scattering produced very little polarization of the scattered light. A small (∼ 4%) negative polarization occurred in the forward scattering hemisphere. Work is continuing here to make scattering measurements using blue light illumination nearly simultaneous with the red HeNe laser wavelength illumination.

No description available.

No description available.

Spectroscopic measurements in the infrared have proven to be a valuable source of information about the Jovian atmosphere. However, numerous questions remain, many of which will be addressed by the Galileo μission, due to arrive at Jupiter in December, 1995. One of the instruments on Galileo is the Near-Infrared Mapping Spectrometer (NIMS), which will measure temperature structure, cheμical composition, and cloud properties. The objective of the work described in this thesis was to investigate the transmittance properties of the Jovian atmosphere and, in particular, to obtain transmittance functions of CH₄ for future use in the planning and interpretation of NIMS measurements. This thesis begins with a review of our current understanding of the Jovian atmosphere (Chapter 1), and a description of the Galileo μission and the design and objectives of NIMS (Chapter 2). It is then shown (Chapter 3) that absorption bands of CH₄ doμinate the nearinfrared spectrum of Jupiter, but that line data for CH₄ are currently inadequate over much of the NIMS spectral range (0.7-5.2 /μi). For the purposes of NIMS, which has a low resolution of 0.25 /μi, the spectrum of CH₄ can be characterised using band models of transmittance as a function of temperature, pressure, and abundance. The theory of band modelling is presented, and previous band-modelling studies of CH₄ are reviewed and are also shown to be inadequate for NIMS (Chapter 4). An experimental investigation was therefore undertaken to record CH₄ spectra under Jovian conditions of low temperature, large abundance, and H₂-broadening. The experimental resources used to obtain these spectra are described (Chapter 5), the generation of the transmittance spectra is discussed, and their quality is assessed (Chapter 6). The range of frequencies and laboratory conditions covered by these spectra (listed in Appendix A) makes them one of the most comprehensive data sets of this kind yet published. These spectra were subsequently used to derive transmittance functions for CH₄ (Chapter 7). A variety of models were fitted to the self-broadened CH₄ spectra, and the Goody and Malkmus random band models, using the Voigt lineshape, are shown to provide the best fits. These two models were then fitted to the combined set of self- and H₂-broadened CH₄ spectra. The parameters fitted with the Goody-Voigt model are included in this thesis (Appendices B and C). Finally, the application of these new band model fits to the problem of Jovian remote sounding is addressed (Chapter 8). This includes an assessment of the reliability of extrapolation to Jovian conditions, a calculation of the level in the Jovian atmosphere that will be sounded by observations of CH₄ absorption, and a calculation of how the uncertainties in the fitted band model will affect the retrieval of atmospheric parameters from NIMS spectra. This thesis concludes with a detailed summary, and with suggestions for future investigations which will help to maximise the return of information from NIMS.

In order to fully understand the role methane (CH₄) plays in the microwave emission spectra of the deep atmospheres of the outer planets, over 280 laboratory measurements of the opacity of ammonia in a methane environment have been made in the 5-20 cm wavelength range. All opacity measurements were made with either 100 or 200 mbars of ammonia and with 1 to 3 bars of added methane in the 330-450K temperature range. A formalism for the absorptivity of ammonia broadened by methane has now been developed and had been applied to the Hanley et al. (Icarus, v. 202, 2009) model for the opacity of ammonia. Due to methane's relatively low abundance at Jupiter (~0.2% by volume), its effect on the microwave spectrum which will be observed by the Juno MWR (Microwave Radiometer) will be minimal. However, these experimental results will significantly improve the understanding of the microwave emission spectrum of Uranus and Neptune where methane plays a more dominant role.