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Orton, G. S.

Publications and source records attributed to Orton, G. S..

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Airborne spectroscopy and spacecraft radiometry of Venus in the far infrared

The first spectral observations of the Venus disk in the 110 to 270 per cm spectral range are reported, made from the Kuiper Airborne Observatory in mid-March 1979, some three months following the start of the Pioneer Venus Orbiter mission. The instrumentation and its differences from earlier flight hardware is discussed. The brightness temperature was 275 K near 110/cm, dropping to 230 K near 270/cm. 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. The atmospheric environment is reviewed with regard to the FIR opacity and possible particle distribution modifications are discussed. It is concluded that the most likely possibility for supplementing the FIR opacity is a population of large particles in the upper cloud with number densities less than one particle per cu cm which has remained undetected by in situ measurements.

Aumann, H. H.↗
NASA NTRS1982

Observational constraints on the atmospheres of Uranus and Neptune from new measurements near 10 micron

Uranus was detected at 10.3, 11.6 and 12.5 micrometers approximately 1 micrometer spectral bandpasses, with respective brightness temperatures of 74.0 + 0.9 or -1.1, 67.6 + 0.5 or -0.7, and 65.5 + 0.6 or -0.7 K and the first detection of Neptune at 10.3 micrometers with a brightness temperature of 77.5 + 0.7 or -0.9 K. We also detected Neptune at 11.36 micrometers with 2% spectral resolution at 81.0 + 0.8 or -0.9 K. The 10 micrometers continuous of both Uranus and Neptune may in part be due to reflected solar radiation as well as thermal emission. If all of the observed flux is reflected light, then the maximum geometric albedo of Uranus is 0.115 + or - 0.020, and that of Neptune is 0.229 + or - 0.043. In the context of previous observations in this region, the maximum stratospheric C2H6 mixing ratio is found to be 3 x 10 to the -8 power for Uranus and 3 x 10 to the -6 power for Neptune. A value for the maximum mixing ratio in the stratosphere of Neptune on the order of 1 - 0.004 appears to be consistent with the available data.

Orton, G. S.↗
NASA NTRS1981

Modification to Scott's method for direct integration of gaseous transmission to improve speed and accuracy

Two limitations to the method of Scott for rapid direct integration of gaseous transmission in a finite spectral interval over an inhomogeneous optical path are discussed. One of these is the inability to use a precomputed form of the Voigt line shape, which can be parameterized via the linewidth alone. This is rectified using the Voigt shape approximation of Kielkopf, which involves a linear combination of three functions which can be pre-computed: the Lorentz shape, the Doppler shape and a correction function. The other limitation involves situations where lines must be treated individually, either line positions must be known with great precision or a uniform value for the widths of all lines in the spectral interval does not describe the transmission adequately. In this case, the strongest lines are treated individually, while the remainder are treated assuming uniform line widths and line positions coincident with positions on the frequency grid, i.e. following Scott's method directly.

Orton, G. S.↗
NASA NTRS1981

Images of Jupiter from the Pioneer 10 and Pioneer 11 Infrared Radiometers - A comparison with visible and 5-micron images

The images with geometric control which present Pioneer 10 and 11 Infrared Radiometer data aquired at Jupiter are compared with 5.0-micron and visible images taken in the same time frame. It is found that (1) at 5.0, 20 and 45 microns, the association of dark and light areas with warm and cool areas, respectively, extends to nearly all features observed on the planet; (2) where the normal association of light and dark visible markings with the zone velocity breaks down, the infrared emission seems to follow the visible cloud structure rather than the zonal velocity structure; and (3) exceptions to the general rule involve 20-micron radiation, which reflects conditions in the 0.1-0.3 bar altitude range. A comparison of Pioneer 10 and 11 images suggests that the South Equatorial Belt became brighter at 20 microns, yet remained constant at other wavelengths between the two encounters.

Orton, G. S.↗
NASA NTRS1981

Spatially resolved absolute spectrophotometry of Saturn - 3390 to 8080 A

A series of spatially resolved absolute spectrophotometric measurements of Saturn was conducted for the expressed purpose of calibrating the data obtained with the Imaging Photopolarimeter (IPP) on Pioneer 11 during its recent encounter with Saturn. All observations reported were made at the Mt. Wilson 1.5-m telescope, using a 1-m Ebert-Fastie scanning spectrometer. Spatial resolution was 1.92 arcsec. Photometric errors are considered, taking into account the fixed error, the variable error, and the composite error. The results are compared with earlier observations, as well as with synthetic spectra derived from preliminary physical models, giving attention to the equatorial region and the South Temperate Zone.

Bergstralh, J. T.↗
NASA NTRS1981

Scientific results from the Pioneer Saturn infrared radiometer

Data on Saturn and its rings are presented, obtained by the Pioneer 11 infrared radiometer in broadband channels, centered at 20 and 45 microns. Assuming symmetry about the equator and a constant flux poleward of 7.5 deg latitude, an average effective temperature of 96.5 + or - 2.5 K indicates a total emission which is 2.8 times that of the absorbed sunlight. Temperatures at the 1 bar level are 137 and 140 K, and a minimum temperature averaging 87 K is registered near the 0.06 bar level. Ring boundaries and optical depths are consistent with those at optical wavelengths. Ring temperatures are 54-86 K on the south side, approximately 54 K on the north side, and at least 67 K in Saturn's shadow.

Orton, G. S.↗
NASA NTRS1981

Atmospheric structure of the outer planets from thermal emission data

Methods for determining atmospheric structure exploit the opacities provided by the collision induced H2 dipole and the nu4 fundamental of CH4. In addition to earth-based observations, useful measurements of thermal emission from Jupiter and Saturn have been or soon will be made by several spacecraft, with results cross-checked with independent radio occultaion results. For Uranus and Neptune, only a limited set of whole-disk earth-based data exists. All the outer planets show evidence for stratospheric temperature inversions; temperature minima range from about 105 K for Jupiter and 87 K for Saturn, to roughly 55 K for Uranus and Neptune. Remaining problems may be resolved by better quantitative understanding of gas and aerosol absorption and scattering properties, chemical composition, and non-LTE source functions. Ultimately, temperature structure results must be supplemented by quantitative energy equilibrium models which will allow some meaning to be given to the relationships between such characteristics as temperature, clouds, incident solar and planetary radiation, and chemical composition.

Orton, G. S.↗
NASA NTRS1980

Saturn's atmospheric temperature structure and heat budget

The effective temperature of Saturn from 30 deg S to 10 deg N is 96.5 + or - 2.5 K. This value is 1.9 K higher than a preliminary estimate (Ingersoll et al., 1980). The atmospheric mole fraction of H2 + He is 90 + or - 3%. This value is derived by comparing infrared and radio occultation data (Kliore et al., 1980) for the same latitude. The high value of the effective temperature suggests that Saturn has an additional energy source besides cooling and contraction. The high mole fraction of H2 suggests that separation of heavier He toward the core may be supplying the additional energy. Atmospheric temperatures in the 60- to 600-mbar range are 2.5 K lower within 7 deg of the equator than at higher latitudes. An almost isothermal layer exists between 60 and 160 mbar at all latitudes.

Orton, G. S.↗
NASA NTRS1980

A line parameter list for the nu2 and nu4 bands of /C-12/H4 and /C-13/H4, extended to J-prime = 25 and its application to planetary atmospheres

Line parameters (transition frequencies, line strengths, line widths, ground state energies and quantum identifications) for the nu2 and nu4 bands of (C-12)H4 and (C-13)H4 have been calculated for J-prime equal to or less than 25 using the simultaneous coupled fitting procedure of Gray and Robiette. Molecular constants for the nu2 band of (C-13)H4 were estimated from isotopic shifts from (C-12)H4 values. Agreement with laboratory spectra, where available, is always well within 1 kayser over the entire spectral range covered by the list. The most serious problem in comparison with laboratory data is the omission of lines belonging to 'hot' bands in this spectral region. This list is valuable in remote sensing problems for sorting out lines of trace species from weak methane lines and for determining the atmospheric opacity in relatively transparent spectral regions. Applications of the parameter list are demonstrated for remote sounding of the Jovian atmosphere.

Orton, G. S.↗
NASA NTRS1980

Infrared scans of Saturn

Scans are presented at five wavelengths between 7.8 and 25 microns north-south along Saturn's central meridian and east-west parallel to the equator through the subearth point. The brightening of Saturn's South Pole at 12.7 microns was more enhanced in 1977 than in 1978 due to the 5 deg greater declination of the polar axis in 1977. There is a plateau in the Southern Hemisphere between -30 and -60 deg latitude in the 7.8 and 12.7 micron scans. The apparent temperature of the rings decreased as Saturn approached the equinox. It is found generally that the strongest ring emission arises from the C ring.

Sinton, W. M.↗
NASA NTRS1980

Infrared scans of Jupiter

Spatial scans at eight wavelengths between 7.8 and 24 microns along Jupiter's meridian and along the Equatorial Zone, the North Equatorial Belt, and the South Tropical Zone are considered. Some features of these scans are differences in brightness temperatures between the Great Red Spot and the surrounding South Tropical Zone, a higher temperature at high northern latitudes than high southern latitudes, equal or possibly higher temperatures of zones than belts at 7.8 microns in contrast to higher temperatures of belts at other observed wavelengths, very strong limb darkening at 8.9 microns possibly due to a large scale height or a nonuniform distribution of solid NH3 particles, and inhomogeneities within belts and zones.

Sinton, W. M.↗
NASA NTRS1980

Pioneer Saturn infrared radiometer - Preliminary results

Preliminary results of the infrared radiometer experiment on Pioneer Saturn are reported. The instrument made use of two broadband channels centered at 20 and 45 microns which scan at a fixed 75-deg angle with respect to the spacecraft spin axis to acquire 10,000 image pairs of Saturn and its rings in the 2.5 h before closest approach, as well as several observations of Titan. The intensities of radiation observed in both bands indicate an effective temperature of 94.4 + or - 3 K for the planet, implying a total emission greater than twice the absorbed sunlight. Infrared data also indicates a molecular abundance of 0.85 for H2 relative to H2 + He, which can be improved by comparing the derived temperature profiles and radio occultation data. Planetary temperatures are found to range from a minimum of 83 to 140 K at the 1 bar level, with differences of 2.5 K between belts and zones up to the 0.06-bar level, while ring temperatures range from 60 to 70 K on the illuminated side and from less than 60 to 67 K in the planet's shadow and average 55 K on the unilluminated side. Preliminary estimates indicate a 45-micron brightness temperature of 80 + or - 10 K for Titan.

Ingersoll, A. P.↗
NASA NTRS1979

A model of the Venus atmosphere from radio, radar, and occultation observations

A model is presented of the atmosphere and surface of Venus which best fits in the least-squares sense the available radio-brightness, radar cross-section, radio interferometric, and Mariner 5 and 10 radio occultation observations. The determinations of the radius of the planet obtained by others from radar time-delay measurements are included in the data set. The values of the adjusted parameters are: molar fraction of CO2 = 95 plus or minus 3%; fraction of combined nitrogen and argon = 5 plus or minus 3%; total atmospheric opacity at a wavelength of 1 cm = 19.4 plus or minus 1.3; mean radius of the surface = 6050.7 plus or minus 0.8 km; mean dielectric constant of the surface = 4.1 plus or minus 0.2, and percentage of total opacity due to chemical species other than CO2 = 45 plus or minus 12. The model temperature and pressure at the mean surface are 755 K and 91.4 atm, respectively.

Muhleman, D. O.↗
NASA NTRS1979

The 12- to 20-micron spectrum of Venus - Implications for temperature and cloud structure

The spectrum of Venus was measured between approximately 500 and 800 kaysers (12 to 20 microns) at a resolution of 3.12 kaysers 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 nu-2 fundamental band at 667 kaysers. 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. 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.

Aumann, H. H.↗
NASA NTRS1978

Multiple frequency sounding of a Jovian cloud

A thermal asymmetry displayed in Pioneer 10 45-micron IR radiometric data between the rising and setting limbs of the Jovian South Equatorial Belt (SEB) between -5.0 and -7.0 deg latitude is examined. A high correlation is found between the longitudinal asymmetry of the SEB at 45 microns and the appearance of Jupiter in 5-micron radiation. It is shown that there was a cooler 'obscuring' cloud within the SEB latitude region which correlates highly with the location of relatively reduced intensities at 45 microns. The cloud-top temperature is estimated on the basis of simultaneous 5- and 45-micron observations

Orton, G. S.↗
NASA NTRS1977

The abundance of acetylene in the atmosphere of Jupiter

The Q and R branches of the C2H2 nu(5) fundamental, observed in emission in an aircraft spectrum of Jupiter near 750/cm, 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 times 10 to the -8th and 6 times 10 to the -9th power, 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 0.01 bar which is near 155 K.

Orton, G. S.↗
NASA NTRS1977

The atmosphere of Jupiter from earth-based and spacecraft observations in the thermal infrared

The temperature and cloud structure, relative abundances of H2 and He, and the global climatology of Jupiter's atmosphere have been deduced from Pioneer 10 and 11 infrared radiometer data, along with earth-based observations of the spectrum at 8-14 and 12-24 microns. The H2 and He abundances are near those expected from 'solar' composition. The effective planetary temperature is 125 + or - 3 K. Temperatures at 1.0 bar are near 165 K and drop to 100-110 K at 0.1 bar; an overlying thermal inversion reaches 133-145 K near 0.03 bar. Temperature profiles for various regions of the planet may be quite similar, with differences due to the presence or absence of a thick cloud near 0.7 bar, close to the temperature where NH3 saturation is expected. Remaining problems in the remote sounding of Jupiter's atmosphere are accurate calibration of the global energy balance, sounding in the presence of significant heterogeneity, and temperature recovery of the thermally inverted stratosphere.

Orton, G. S.↗