Pioneer 11 infrared radiometer experiment: the global heat balance of jupiter

Data obtained by the infrared radiometers on the Pioneer 10 and Pioneer 11 spacecraft, over a large range of emission angles, have indicated an effective temperature for Jupiter of 125 degrees +/- 3 degrees K. The implied ratio of planetary thermal emission to solar energy absorbed is 1.9+/-0.2, a value not significantly different from the earth-based estimate of 2.5+/-0.5.     

Masses of the galilean satellites of jupiter

Numerical data derived from the observation of the four great satellites of Jupiter are compared with the values obtained through Sampson's theory by using the new JPL (Jet Propulsion Laboratory) system of masses. It is not possible to fit the coefficient of the free oscillation in the longitude of Ganymede, whose argument is l(3) - omega(4) (the mean longitude of Ganymede referred to the proper apse of Callisto), and the mass of Callisto derived from the path of Pioneer 10.     

Galilean satellites of jupiter: 12.6-centimeter radar observations

Observations of the Galilean satellites with the radar system at the Arecibo Observatory, Puerto Rico, show that their surfaces are highly diffuse scatterers of radio waves of length 12.6 centimeters; spectra of the radar echoes are asymmetric and broad. The geometric radar albedos for the outer three satellites-0.42 +/- 0.10, 0.20 +/- 0.05, and 0.09 +/- 0.02 for Europa, Ganymede, and Callisto, respectively-show about the same relative decreases as do the optical albedos, although the latter presumably bear only on material much nearer the surface. Radii of 1420 +/- 30, 2640 +/- 80, and 2360 +/- 70 kilometers for Europa, Ganymede, and Callisto were determined from the radar data and are in good agreement with the corresponding optically derived values. Io, observed successfully only once, appears to have an albedo comparable to Ganymede's, but no radius was estimated for it.     

Infrared observations of the jovian system from voyager 2

Infrared spectra obtainedfrom Voyager 2 have provided additional data on the Jovian system, complementing those obtained from Voyager 1. The abundance ratio of ethane to acetylene in Jupiter's atmosphere appears to be about three times larger in the polar regions than at lower latitudes. A decidedly hemispherical asymmetry exists, with somewhat higher ratios prevailing in northern latitudes. An overall increase in the abundance ratio by a factor of about 1.7 appears to have occurred between the Voyager 1 and 2 encounters. Global brightness temperature maps of Jupiter at 226 and 602 cm(-1) exhibit a large amount of local- and planetary-scale structure, as well as temporal variability. Although heterogeneous cloud structure and ammonia concentration in the lower troposphere may contribute to the appearance of the 226-cm(-1) map, the detail in the 602-cm(-1) maps probably represents the actual horizontal thermal structure near the tropopause and suggests that dynamical heating and cooling processes are important. Low-latitude surface temperatures on the Galilean satellites rangefrom approximately 80 K on the dark sides to 155 K at the subsolar point on Callisto. Below a thin insulating layer, the thermal inertia of Callisto is somewhat greater than that of Earth's moon. Upper limits on the infrared optical depth of the Jovian ring rangingfrom approximately 3 x 10(-4) at 250 cm(-1) to 3 x 10(-3) at 600 cm(-1) have been found.     

The jupiter system through the eyes of voyager 1

The cameras aboard Voyager 1 have provided a closeup view of the Jupiter system, revealing heretofore unknown characteristics and phenomena associated with the planet's atmosphere and the surfaces of its five major satellites. On Jupiter itself, atmospheric motions-the interaction of cloud systems-display complex vorticity. On its dark side, lightning and auroras are observed. A ring was discovered surrounding Jupiter. The satellite surfaces display dramatic differences including extensive active volcanismn on Io, complex tectonism on Ganymnede and possibly Europa, and flattened remnants of enormous impact features on Callisto.     

Infrared speckle observations of io: an eruption in the loki region

Speckle observations of Jupiter's satellite Io at a wavelength of 5 micrometers during July 1984 resolved the disk and showed emission from a hot spot in the Loki region. The hot spot contributed a flux approximately equal to 60 percent of that from the disk. Images reconstructed by means of the Knox-Thompson algorithm showed the spot moving across the disk as the satellite rotated. It was located at 301 degrees +/- 6 degrees west longitude, 10 degrees +/- 6 degrees north latitude, and had a radiance of (2.96 +/- 0.54) x 10(22) ergs sec(-1) cm(-1) sr(-1)/A where A is the area of the spot. For an assumed temperature of 400 K, the area of the source would be 11,400 square kilometers. An active "lava lake" similar to that seen by Voyager may be the source of the infrared emission.     

Jupiter's Spectrum Between 12 and 24 Micrometers

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).     

Deuterated methane observed on saturn

Absorptions for the V(2) band of deuterated methane (CH(3)D) have been observed in the 5-micron spectrum of Saturn, obtained with a Fourier transform spectrometer. Analysis of the band yields a CH(3)D abundance of 2.6 +/- 0.8 centimeter-amagat and a temperature of 175 +/- 30 K for the mean level of spectroscopic line formation. This temperature indicates that a substantial portion of Saturn's flux at 5 microns is due to thermal radiation, and that we are therefore looking fairly deep into its atmosphere, as is the case for the Jupiter 5-micron window. This CH(3)D abundance leads to a deuteriumlhydrogen ratio of about 2 x 10(-5) in Saturn's atmosphere. This ratio is much lower than the terrestrial value but comparable to that determined for Jupiter and may be taken as representative of the deuteriumlhydrogen ratio in the solar system at the time of its formation.     

Io volcanism seen by new horizons: a major eruption of the Tvashtar volcano

Jupiter's moon Io is known to host active volcanoes. In February and March 2007, the New Horizons spacecraft obtained a global snapshot of Io's volcanism. A 350-kilometer-high volcanic plume was seen to emanate from the Tvashtar volcano (62 degrees N, 122 degrees W), and its motion was observed. The plume's morphology and dynamics support nonballistic models of large Io plumes and also suggest that most visible plume particles condensed within the plume rather than being ejected from the source. In images taken in Jupiter eclipse, nonthermal visible-wavelength emission was seen from individual volcanoes near Io's sub-Jupiter and anti-Jupiter points. Near-infrared emission from the brightest volcanoes indicates minimum magma temperatures in the 1150- to 1335-kelvin range, consistent with basaltic composition.     

Extreme ultraviolet observations from voyager 1 encounter with saturn

The global hydrogen Lyman alpha, helium (584 angstroms), and molecular hydrogen band emissions from Saturn are qualitatively similar to those of Jupiter, but the Saturn observations emphasize that the H(2) band excitation mechanism is closely related to the solar flux. Auroras occur near 80 degrees latitude, suggesting Earth-like magnetotail activity, quite different from the dominant Io plasma torus mechanism at Jupiter. No ion emissions have been detected from the magnetosphere of Saturn, but the rings have a hydrogen atmosphere; atomic hydrogen is also present in a torus between 8 and 25 Saturn radii. Nitrogen emission excited by particles has been detected in the Titan dayglow and bright limb scans. Enhancement of the nitrogen emission is observed in the region of interaction between Titan's atmosphere and the corotating plasma in Saturn's plasmasphere. No particle-excited emission has been detected from the dark atmosphere of Titan. The absorption profile of the atmosphere determined by the solar occultation experiment, combined with constraints from the dayglow observations and temperature information, indicate that N(2) is the dominant species. A double layer structure has been detected above Titan's limb. One of the layers may be related to visible layers in the images of Titan.     

1979J3: Discovery of a Previously Unknown Satellite of Jupiter

During a detailed search of Voyager 1 frames for additional observations of the satellite 1979J1, two small dark spots were observed in transit in several consecutive wide-angle frames of the Jovian atmosphere. The size, spacing, and motion of these pairs of dark spots indicated that they were the images of 1979J1 and its shadow. Subsequent analysis of images spanning 6 days, however, proved that the satellite observed in these Voyager 1 frames would have been occulted by Jupiter at the times of the Voyager 2 images of 1979J1 and was, therefore, a new satellite. It was subsequently found in transit on Voyager 2 images within 13 degrees of the Voyager 1 prediction. Its period is 7 hours 4 minutes 30 seconds +/- 3 seconds, and its mean distance is 1.793 Jupiter radii (Jupiter radius = 71,400 kilometers). The observable profile appears to be roughly circular with a diameter of 40 kilometers, and the albedo is approximately 0.05, similar to Amalthea's.     

Dust measurements at high ecliptic latitudes

Along Ulysses' path from Jupiter to the south ecliptic pole, the onboard dust detector measured a dust impact rate that varied slowly from 0.2 to 0.5 impacts per day. The dominant component of the dust flux arrived from an ecliptic latitude and longitude of 100 + 10 degrees and 280 degrees +/- 30 degrees which indicates an interstellar origin. An additional flux of small particles, which do not come from the interstellar direction and are unlikely to be zodiacal dust grains, appeared south of -45 degrees latitude. One explanation is that these particles are beta-meteoroids accelerated away from the sun by radiation pressure and electromagnetic forces.     

Sea level variation as an indicator of Florida current volume transport: comparisons with direct measurements

Sea level measurements from tide gauges at Miami, Florida, and Cat Cay, Bahamas, and bottom pressure measurements from a water depth of 50 meters off Jupiter, Florida, and a water depth of 10 meters off Memory Rock, Bahamas, were correlated with 81 concurrent direct volume transport observations in the Straits of Florida. Daily-averaged sea level from either gauge on the Bahamian side of the Straits was poorly correlated with transport. Bottom pressure off Jupiter had a linear coefficient of determination ofr(2) = 0.93, and Miami sea level, when adjusted for weather effects, had r(2) = 0.74; the standard errors of estimating transports were +/- 1.2 x 10(6) and +/- 1.9 x 10(6) cubic meters per second, respectively. A linear multivariate regression, which combined bottom pressure, weather, and the submarine cable observations between Jupiter and the Bahamas, had r(2) = 0.94 with a standard error of estimating transport of +/- 1.1 x 10(6) cubic meters per second. These results suggest that a combination of easily obtained observations is sufficient to adequatelv monitor the daily volume transport fluctuations of the Florida Current.     

Energetic electrons in the magnetosphere of jupiter

Observations of energetic electrons ( greater, similar 0.07 million electron volts) show that the outer magnetosphere of Jupiter consists of a thin disklike, quasitrapping region extending from about 20 to 100 planetary radii (R(J)). This magnetodisk is confined to the vicinity of the magnetic equatorial plane and appears to be an approximate figure of revolution about the magnetic axis of the planet. Hard trapping is observed within a radial distance of about 20 R(J). The omnidirectional intensity J(0) of electrons with energy greater, similar 21 million electron volts within the region 3 r 20 R(J) is given by the following provisional expression in terms of radial distance r and magnetic latitude theta: J(0) = 2.1 x 10(8) exp[-(r/a) - (theta/b)(2)]. In this expression J(0) is particles per square centimeter per second; a = 1.52 R(J) for 3 相似文献   

Infrared observations of the neptunian system

The infrared interferometer spectrometer on Voyager 2 obtained thermal emission spectra of Neptune with a spectral resolution of 4.3 cm(-1). Measurements of reflected solar radiation were also obtained with a broadband radiometer sensitive in the visible and near infrared. Analysis of the strong C(2)H(2) emission feature at 729 cm(-1) suggests an acetylene mole fraction in the range between 9 x 10(-8) and 9 x 10(-7). Vertical temperature profiles were derived between 30 and 1000 millibars at 70 degrees and 42 degrees S and 30 degrees N. Temperature maps of the planet between 80 degrees S and 30 degrees N were obtained for two atmospheric layers, one in the lower stratosphere between 30 and 120 millibars and the other in the troposphere between 300 and 1000 millibars. Zonal mean temperatures obtained from these maps and from latitude scans indicate a relatively warm pole and equator with cooler mid-latitudes. This is qualitatively similar to the behavior found on Uranus even though the obliquities and internal heat fluxes of the two planets are markedly different. Comparison of winds derived from images with the vertical wind shear calculated from the temperature field indicates a general decay of wind speed with height, a phenomenon also observed on the other three giant planets. Strong, wavelike longitudinal thermal structure is found, some of which appears to be associated with the Great Dark Spot. An intense, localizd cold region is seen in the lower stratosphere, which does not appear to be correlated with any visible feature. A preliminary estimate of the effective temperature of the planet yields a value of 59.3 +/- 1.0 kelvins. Measurements of Triton provide an estimate of the daytime surface temperature of 38(+3)(-4) kelvins.     

Atomic hydrogen on Mars: measurements at solar minimum

The Copernicus Orbiting Astronomical Observatory was used to obtain measurements of Mars Lyman-alpha (1215.671-angstrom) emission at the solar minimum, which has resulted in the first information on atomic hydrogen concentrations in the upper atmosphere of Mars at the solar minimum. The Copernicus measurements, coupled with the Viking in situ measurements of the temperature (170 degrees +/- 30 degrees K) of the upper atmosphere of Mars, indicate that the atomic hydrogen number density at the exobase of Mars (250 kilometers) is about 60 times greater than that deduced from Mariner 6 and 7 Lyman-alpha measurements obtained during a period of high solar activity. The Copernicus results are consistent with Hunten's hypothesis of the diffusion-limited escape of atomic hydrogen from Mars.     

Infrared observations of the uranian system

The infrared interferometer spectrometer (IRIS) on Voyager 2 recorded thermal emission spectra of Uranus between 200 and 400 cm(-1) and of Miranda and Ariel between 200 and 500 cm(-1) with a spectral resolution of 4.3 cm(-1). Reflected solar radiation was also measured with a single-channel radiometer sensitive in the visible and near infrared. By combining IRIS spectra with radio science results, a mole fraction for atmospheric helium of 0.15 +/- 0.05 (mass fraction, 0.26 +/- 0.08) is found. Vertical temperature profiles between 60 and 900 millibars were derived from average polar and equatorial spectra. Temperatures averaged over a layer between 400 to 900 millibars show nearly identical values at the poles and near the equator but are 1 or 2 degrees lower at mid-latitudes in both hemispheres. The cooler zone in the southern hemisphere appears darker in reflected sunlight than the adjacent areas. An upper limit for the effective temperature of Uranus is 59.4 kelvins. Temperatures of Miranda and Ariel at the subsolar point are 86 +/- 1 and 84 +/- 1 kelvins, respectively, implying Bond albedos of 0.24 +/- 0.06 and 0.31 +/- 0.06, respectively. Estimates of phase integrals suggest that these satellites have unusual surface microstructure.     

Ultraviolet spectrometer observations of neptune and triton

Results from the occultation of the sun by Neptune imply a temperature of 750 +/- 150 kelvins in the upper levels of the atmosphere (composed mostly of atomic and molecular hydrogen) and define the distributions of methane, acetylene, and ethane at lower levels. The ultraviolet spectrum of the sunlit atmosphere of Neptune resembles the spectra of the Jupiter, Saturn, and Uranus atmospheres in that it is dominated by the emissions of H Lyman alpha (340 +/- 20 rayleighs) and molecular hydrogen. The extreme ultraviolet emissions in the range from 800 to 1100 angstroms at the four planets visited by Voyager scale approximately as the inverse square of their heliocentric distances. Weak auroral emissions have been tentatively identified on the night side of Neptune. Airglow and occultation observations of Triton's atmosphere show that it is composed mainly of molecular nitrogen, with a trace of methane near the surface. The temperature of Triton's upper atmosphere is 95 +/- 5 kelvins, and the surface pressure is roughly 14 microbars.     

Crystal Structure of Benzene II at 25 Kilobars

Crystals of a high-pressure form of benzene (benzene 11) were grown in the diamond-anvil pressure cell at elevated temperature and pressure from the transition of solid I to solid II. X-ray precession data were obtained from a single-crystal in the high-pressure cell. At 21 degrees C and about 25 kilobars, benzene II crystallizes in the monoclinic system with a = 5.417 +/- 0.005 angstroms (S.D.), b = 5.376 +/- 0.019 angstroms, c = 7.532 +/- 0.007 angstroms, beta = 110.00 degrees +/- 0.08 degrees , space group P2(1)/ c, Pc= 1.26 grams per cubic centimeter. The crystal structure was solved by generating all possible molecular packing configurations and calculating structure factors, reliability factors, and packing energies for each configuration. This procedure produced a unique solution for the molecular packing of benzene II.     

Preliminary infrared radiometry of the night side of mercury from mariner 10

The infrared radiometer on Mariner 10 measured the thermal emission from the planet with a spatial resolution element as small as 40 kilometers in a broad wavelength band centered at 45 micrometers. The minimum brightness temperature (near local midnight) in these near-equatorial scans was 100 degrees K. Along the track observed, the temperature declined steadily from local sunset to near midnight, behaving as would be expected for a homogeneous, porous material with a thermal inertia of 0.0017 cal cm(-2) sec(-(1/2)) degrees K(-1), a value only slightly larger than that of the moon. From near midnight to dawn, however, the temperature fluctuated over a range of about 10 degrees K, implying the presence of regions having thermal inertia as high as 0.003 cal cm(-2) sec-(1/2) degrees K(-1).