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Price, M. J.

Publications and source records attributed to Price, M. J..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Saturn - UBV photoelectric pinhole scans of the disk. II

During the 1980 Saturn apparition, UBV pinhole scans of the disk were obtained with a photoelectric area-scanning photometer. An analysis of these data reveals that the atmosphere of Saturn can be represented by a finite clear H2 layer overlying a semiinfinite absorbent aerosol haze. The extent of the clear H2 region appears to be latitude-dependent; the H2 column density varies systematically from about 15 km-am over the equatorial and polar regions to about 31 km-am at temperate latitudes. A previous conclusion that the aerosol haze is strongly absorbent in the UV is confirmed; its effective U-band single-scattering albedo is about 0.4. Latitudinal disk structure at visual wavelengths appears to be the result of local variations in the volume density of absorbent particles in the aerosol layer.

Price, M. J.↗
NASA NTRS1980

Outer planet investigations using a CCD camera system

Problems related to analog noise, data transfer from the camera buffer to the storage computer, and loss of sensitivity of a two dimensional charge coupled device imaging system are reported. To calibrate the CCD system, calibrated UBV pinhole scans of the Saturn disk were obtained with a photoelectric area scanning photometer. Atmospheric point spread functions were also obtained. The UBV observations and models of the Saturn atmosphere are analyzed.

Price, M. J.↗
NASA NTRS1979

Uranus - Disk structure within the 7300-A methane band

Orthogonal narrow-band (100 A) photoelectric slit scan photometry of Uranus has been used to infer the basic two-dimensional structure of the disk within the 7300-A methane band. Numerical image reconstruction and restoration techniques have been applied to quantitatively estimate the degrees of polar and limb brightening on the planet. Through partial removal of atmospheric smearing, an effective spatial resolution of approximately 0.9 arcsec has been achieved. Peak polar, limb, and central intensities on the disk are in the respective proportions 3:2:1. In addition, the bright polar feature is displaced from the geometric pole towards the equator of the planet.

Price, M. J.↗
NASA NTRS1979

Uranus - Narrow-waveband disk profiles in the spectral region 6000 to 8500 Angstroms

New narrow-band (100 A) photoelectric slit scan photometry of Uranus has been obtained in the spectral region 6000 to 8500 A. Coarse radial intensity profiles in seven wavebands are presented. Results of the investigation confirm earlier studies of limb brightening on the Uranus disk, but not all strong CH4 absorption bands are found to exhibit limb brightening. Specifically, the CH4 bands at 8000 and 8500 A show pronounced apparent limb darkening. Polar brightening may be responsible for the phenomenon. If so, an aerosol haze with a local optical thickness of approximately 0.5 or greater would be required. Visibility of the dense cloud layer located deep in the atmosphere might also cause apparent limb darkening. If so, the maximum permitted CH4/H2 mixing ratio in the visible atmosphere would correspond to 3 times the solar value.

Price, M. J.↗
NASA NTRS1979

Saturn - UBV photoelectric pinhole scans of the disk

UBV photoelectric pinhole scans of Saturn's disk are reported. The data are interpreted by using elementary radiative-transfer models to describe scattering in the atmosphere above the visible haze layer. Limits are placed on the optical thickness of the region above the haze, and the results are discussed in terms of the probable structure of Saturn's upper atmosphere. It is shown that a model involving conservative Rayleigh scattering by hydrogen molecules above an opaque haze or cloud deck provides a satisfactory quantitative description of the scattering properties of Saturn's upper atmosphere.

Franz, O. G.↗
NASA NTRS1978

Limb brightening on Uranus - An interpretation of the lambda 7300 A methane band

Measurements of limb brightening on the Uranus disk within the lambda 7300 A CH4 band are interpreted using an elementary inhomogeneous radiative transfer model to describe the atmosphere. A two layer model which consists of a finite, optically thin, region of conservatively scattering particles overlying a semi-infinite clear H2-CH4 atmosphere satisfactorily explains the observations. The maximum optical thickness of the upper layer appears to lie in the range 0.1 to 0.2. The CH4/H2 mixing ratio in the lower layer is larger than the corresponding solar value by a factor on the order of three or greater. The results are discussed briefly in terms of current models of the Uranus atmosphere.

Price, M. J.↗
NASA NTRS1978

Limb brightening on Uranus - The visible spectrum. II

A detailed analysis is presented of photoelectric area-scanning photometry of the Uranus disk obtained during the 1976 apparition. Coarse quantitative information on the true radial intensity distribution over the Uranus disk is derived in four selected wavebands. Lack of circular symmetry in the intensity distributions indicates the presence of disk structure, especially polar brightening, in each waveband. For the 6190-A CH4 band, the distribution corresponds to a uniform disk upon which a hint of polar brightening is superimposed. For the 6400-A region, moderate limb darkening is found. It is pointed out that the coarse analytical technique used in the analysis to explore the information content of the photometric scans of Uranus has several basic limitations. Direct deconvolution of the Uranus scans is required to thoroughly investigate the two-dimensional photometric structure of its disk.

Price, M. J.↗
NASA NTRS1977

Uranus - Limb and polar brightening at 7300 A

Pinhole photoelectric area-scanning photometry of the Uranus disk demonstrates directly the existence of both limb and polar brightening in the 7300 A CH4 band. Polar brightening, which appears to be present also at continuum wavelengths, is interpreted as being caused by scattering in a thin aerosol haze located over the polar region.

Franz, O. G.↗
NASA NTRS1977

On probing the outer planets with the Raman effect

The paper examines the feasibility of using the H2 rotational Raman spectrum to study the physical structure of the atmospheres of the outer planets. Computations of the strengths of the S(0) and S(1) lines are made for a wide range of physical conditions on the basis of a semi-infinite homogeneous pure H2 atmospheric model. Initial applications of the Raman probe technique to Jupiter and Uranus are reported.

Price, M. J.↗
NASA NTRS1977

Anisotropic optical scattering within Saturn's rings

Visual photometric-function data for Saturn's rings are analyzed in terms of elementary anisotropic-scattering radiative-transfer models which involve the Henyey-Greenstein function. Limits are placed on the combinations of single-scattering albedo and backscattering directivity which are permitted by observation. Particles with both microscopic and macroscopic lunarlike scattering properties are excluded by the analysis. Results are consistent with the ring particles being nearly pure spherical conglomerates of H2O frost.

Price, M. J.↗
NASA NTRS1976

Limb brightening on Uranus - The visible spectrum

Results are presented for pinhole and slit narrowband photoelectric area-scanning photometry of the Uranus disk at eight central wavelengths ranging from 5600 to 7500 A. The observations were undertaken to detect limb brightening on the planet and to study the nature of its disk profile as a function of geometrical albedo. A coarse analysis of the results shows that the disk must exhibit limb brightening in the two CH4 bands at 6190 and 7300 A relative to all other wavebands investigated. Except for the two CH4 bands, the shapes and widths of the images are found to be essentially identical; point-spread-function data for all wavebands indicate no significant variation in the representative Gaussian l/e width with wavelength. A fine analysis of the data reveals absolute limb brightening in the 7300-A CH4 band and absolute limb darkening in the adjacent wavebands. These results are shown to be consistent with the hypothesis that clouds are absent from the visible atmosphere of Uranus.

Price, M. J.↗
NASA NTRS1976

Infrared thermal models for Saturn's ring

Infrared (10 and 20 microns) thermal emission data for Saturn's rings are discussed in terms of simple isothermal radiative transfer models of finite optical thickness. Recent brightness temperature measurements, corresponding to essentially maximum ring tilt, indicate that optical single scattering albedos less than 0.75 are required to provide sufficient heating of the ring material. Reconciliation with analyses of the optical scattering properties of the ring requires the backscattering efficiency to be even higher than for a macroscopic sphere. Historical brightness temperature measurements are used to show that no unique isothermal ring model exists. Instead, a temperature gradient perpendicular to the ring plane appears to be present.

Price, M. J.↗
NASA NTRS1975

Illumination of Saturn's ring by the ball. I - Preliminary results

Indirect solar illumination of Saturn's ring via scattering from the ball of the planet provides a new ground-based observational technique for studying the single scattering albedo and phase function of the individual particles. Information concerning optical thickness may also be obtained. Essentially complete phase angle coverage can be achieved by studying the variation with azimuth of the indirect contribution to the surface brightness of the ring. Initial application of the technique is reported. The indirect contribution to the radiation scattered from the ring has been marginally detected by electronographic areal photometry. The results have been interpreted using simple scattering models. The photometric accuracy was insufficient to permit investigation of departures from isotropic scattering. But high single scattering albedos, and an essentially opaque ring, are indicated.

Price, M. J.↗
NASA NTRS1975

Saturn's rings and Pioneer 11

Quantitative predictions of the diffuse reflection and transmission properties of Saturn's rings, relevant to the September 1979 Pioneer 11 flyby, are presented. Predictions are based on an elementary anisotropic scattering model. Interparticle separations are considered to be sufficiently large that mutual shadowing is negligible. Likely ranges in both the single scattering albedo and perpendicular optical thickness of the ring are considered. Situations of pronounced back-scattering and of isotropic scattering are treated individually. Spacecraft measurement of the radiation suffering diffuse scattering by the ring can provide a useful test of the basic ring model.

Price, M. J.↗
NASA NTRS1974

Mars - Clearing of the 1971 dust storm

A semiquantitative analysis of clearing in the 1971 great dust storm on Mars is presented as a function of time and altitude, using Mariner 9 orange- and visual-light photos. Steady settling of dust approximately accounts for the decline of the storm after Dec. 22, 1971. Continuous settling cannot be invoked prior to that date; injection of dust into the atmosphere, i.e., a storm resurgence, occurred in mid-December 1971. Theoretical models of optical depth vs time are developed for various distributions of particles in the atmosphere. By interpreting settling in terms of Stokes' law, estimates of the maximum radii of dust particles throughout the atmosphere have been obtained. Models which best account for the dust-storm decline indicate particles less than 5 microns in diameter high in the atmosphere, with a concentration of larger particles near the ground in the lowest parts of Mars.

Hartmann, W. K.↗
NASA NTRS1973

The scattering mean free path in the Uranian atmosphere

New measurements of the equivalent widths of the 4.0 S(0) and S(1) H2 quadrupole lines in the Uranian spectrum have been obtained using high dispersion (4.12 A/mm) image-tube spectrography. The measured equivalent widths are 62 plus or minus 19 mA and 58 plus or minus 13 mA for the S(0) and S(1) lines, respectively. Curve-of-growth analysis in terms of a reflecting layer model yields an H2 column density of 780 (+940 or -330) km amagat and a temperature of 78 (+80 or -24) K. Interpretation using a semiinfinite, homogeneous, isotropically scattering model for line formation yields a scattering mean free path at 6400 A of 550 plus or minus 250 km amagat. Quoted errors for both the H2 column density and the scattering mean free path include the effect of uncertainty in the choice of atmospheric temperature. The results are discussed in terms of current models for the Uranian atmosphere.

Price, M. J.↗