Modelling atmospheric scatterers using spacecraft observations

Voyager images of Triton indicate considerable spatial variability in the concentration of at least two different scattering components in the atmosphere. Data from high phase angle limb scans were fit to Mie scattering models to derive mean particle sizes, number densities, and vertical extent for both types of scattering material at ten different locations between 15 deg S and 70 deg S. These fits reveal a thin haze at latitudes equatorward of 25-30 deg S. The imaging data can be fit reasonably well by both conservatively scattering and absorbing hazes with particle sizes near 0.18 micron and optical depths of order 0.001-0.01. Rayleigh scattering haze fits the imaging data somewhat less well, and can be totally ruled out by combining the imaging and UVS measurements. At high southern latitudes, Triton displays clouds below an altitude of approximately 8 km, as well as the haze at higher altitudes. The clouds have particle sizes which may range from 0.7-2.0 microns, or may be near 0.25 micron. The atmospheric optical depth poleward of 30 deg S must be generally greater than 0.1, but need not be more than 0.3. Horizontal inhomogeneities are quite noticeable, especially at longitudes east of (i.e., higher than) 180 deg

Modelling Atmospheric Scattering Using Spacecraft Observations

The period covered by this cooperative agreement included the analysis of data from the Voyager encounter with Neptune and Triton and the primary Galileo mission to Jupiter (including the Galileo Probe entry into Jupiter's atmosphere), as well as continued work on Uranus' seasonal variability using the Voyager encounter data as a baseline

An Analysis of Neptune's Stratospheric Haze Using High-Phase-Angle Voyager Images

We have inverted high-phase-angle Voyager images of Neptune to determine the atmospheric extinction coefficient as a function of altitude and the scattering phase function at a reference altitude. Comparisons between theoretical model and observations help separate the contributions from molecular Rayleigh and aerosol scattering and help determine the variation of the aerosol size, concentration, and scattering properties with altitude. Further comparisons between models and data allow us to place constraints on the location and composition of the hazes, the concentration and downward flux of certain condensible hydrocarbon gases, the eddy diffusion coefficient in the lower stratosphere, and the thermal profile in parts of Neptune's stratosphere. We find that a distinct stratospheric haze layer exists near 12(sub -1, sup +1) mbar in Neptune's lower stratosphere, most probably due to condensed ethane. The derived stratospheric haze production rate of 1.0(sub -0.3, sup +0.2) x 10(exp -15) g cm(exp -2) sec(exp -1) is substantially lower than photochemical model predictions. Evidence for hazes at higher altitudes also exists. Unlike the situation on Uranus, large particles (0.08-0.11 microns) may be present at high altitudes on Neptune (e.g., near 0.5 mbar), well above the region in which we expect the major hydrocarbon species to condense. Near 28 mbar, the mean particle size is about 0.13(sub -0.02, sup +0.02) microns with a concentration of 5(sub -3, sup +3) particles cm(exp -3). The cumulative haze extinction optical depth above 15 mbar in the clear filter is approx. 3 x 10(exp -3), and much of this extinction is due to scattering rather than absorption; thus, if our limb-scan sites are typical, the hazes cannot account for the stratospheric temperature inversion on Neptune and may not contribute significantly to atmospheric heating. We compare the imaging results with the results from other observations, including those of the Voyager Photopolarimeter Subsystem, and discuss differences between Neptune and Uranus

Properties Of Microwave Cavities Containing Magnetic Resonant Samples

Properties of TE011 cylindrical, microwave cavities containing cylindrical samples of various radii and dielectric constants are calculated. The properties considered are the resonant frequency, quality factor (Q), relevant magnetic filling factor for spin transitions (ε), and a signal sensitivity factor (Qε) for a lossless sample. Sample sizes range from zero radius to full cavity radius with some experimental data on less than full length samples. The choice of dielectric constants ranges from one to sixteen. The data are presented in dimensionless form since they will be of use to other ESR experimentalists. It is shown that use of large samples is undesirable even if they are lossless. Furthermore, elongated cavities (D/L ratios less than one) are to be preferred over shortened cavities. © 1973 The American Institute of Physics

On the relationship between secular brightness changes of Titan and solar variability

Titan’s geometric albedo varied noticeably from 1972 to 1978, in phase with variations in solar activity [Lockwood and Thompson, 1979]. We carry out a series of radiative transfer and aerosol formation calculations in order to demonstrate the feasibility of the following scenario for these secular brightness changes: solar activity changes, especially in the UV output of the Sun, result in alterations to the mass production rate of aerosols in Titan’s atmosphere, which lead to modifications of their microphysical properties. The latter, in turn, cause the albedo to vary. Current estimates of the change in the solar UV radiation below the dissociation limit of methane imply alterations to the mean radius of the aerosols over an 11-yr solar cycle that are consistent in sign and magnitude with those required to explain the observed secular brightness changes

Vertical Structure in Outer Planet Atmospheres

The period covered by this cooperative agreement included: 1) the analysis of data acquired by both Voyager spacecraft during their encounters with Saturn in 1979 and 1980; 2) work on Uranus' seasonal variability and transient albedo features on both Uranus and Neptune using observations made by the Hubble Space Telescope beginning in 2000; 3) a search for lightning on Jupiter using HST; and 4) the analysis of Pathfinder images of Martian surface features

Modelling Atmospheric Scatterers Using Spacecraft Observations

This project report reviews the analysis of data from the Voyager encounter with Neptune and Triton, and the primary Galileo mission to Jupiter. The project included analysis of the images from Voyager of the limb images from Neptune and Triton. Also included in the project was analysis of the Images from Galileo of Venus' and Jupiter's limb. The project work on the latitude bands and temporal variations on Uranus using the images from Voyager is summarized. Also, work on information from the Galileo Probe's Nephelometer is also covere