Infrared images of jupiter at 5-micrometer wavelength during the voyager 1 encounter

A coordinated program to observe Jupiter at high spatial resolution in the 5-micrometer wavelength region was undertaken to support Voyager 1 imaging and infrared radiation experiment targeting. Jupiter was observed over a 5-month period from Palomar and Mauna Kea observatories. The frequency of observations allowed the selection of interesting areas for closer Voyager examination and also provided good short-term monitoring of variations in cloud morphology. Significant global changes in the 5-micrometer distribution are seen over this time period.     

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.     

Volcanic hotspots on io: stability and longitudinal distribution

We report the first results of a program to determine the longitudinal distribution of volcanic activity on Jupiter's satellite Io. Infrared measurements at 8.7, 10, and 20 micrometers have been taken at a variety of orbital longitudes: strong variation in the 8.7- and 10-micrometer flux with longitude demonstrates that infrared emission arising from volcanic hotspots on Io is strongly concentrated in a few locations. Analysis of these data suggests that the active volcanic regions observed by the Voyager experimenters are still active, particularly the region around the feature known as Loki. Another source of flux, although of somewhat smaller magnitude, is indicated on the opposite hemisphere. If these sources are the only major volcanic centers on Io, then current global heat flow estimates must be revised downward. However, heat flow from as yet unobserved longitudes, hotspots at high latitudes, and conducted heat flow must still be measured.     

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.     

Photometric observations of jupiter at 2400 angstroms

The photopolarimeter instrument on Voyager 2 was used to obtain a map of Jupiter at an effective wavelength of 2400 angstroms. Analysis of a typical north-south swath used to make this map shows strong absorption at high latitudes by a molecular or particulate constituent in the Jovian atmosphere. At 65 degrees north latitude, the absorbing constituent extends to altitudes above the 50-millibar pressure level.     

1979J2: The Discovery of a Previously Unknown Jovian Satellite

During a detailed examination of imaging data taken by the Voyager 1 spacecraft within 4.5 hours of its closest approach to Jupiter, a shadow-like image was observed on the bright disk of the planet in two consecutive wide-angle frames. Analysis of the motion of the image on the Jovian disk proved that it was not an atmospheric feature, showed that it could not have been a shadow of any satellite known at the time, and allowed prediction of its reappearance in other Voyager 1 frames. The satellite subsequently has been observed in transit in both Voyager 1 and Voyager 2 frames; its period is 16 hours 11 minutes 21.25 seconds +/- 0.5 second and its semimajor axis is 3.1054 Jupiter radii (Jupiter radius = 7.14 x 10(4) kilometers). The profile observed when the satellite is in transit is roughly circular with a diameter of 80 kilometers. It appears to have an albedo of approximately 0.05, similar to Amalthea's.     

Voyager 2: energetic ions and electrons in the jovian magnetosphere

The Voyager 2 encounter has enhanced our understanding of earlier results and provided measurements beyond 160 Jupiter radii (R(J)) in the magnetotail. Significant fluxes of energetic sulfur and oxygen nuclei (4 to 15 million electron volts per nucleon) of Jovian origin were observed inside 25 R(J), and the gradient in phase space density at 12 R(J) indicates that the ions are diffusing inward. A substantially longer time delay versus distance was found for proton flux maxima in the active hemisphere in the magnetotail at Jovicentric longitudes lambda(III), = 260 degrees to 320 degrees than in the inactive hemisphere at lambda(III), = 85 degrees to l10 degrees . These delays can be related to the radial motion of plasma expanding into the magnetotail, and differences in the expansion speeds between the active and inactive hemispheres can produce rarefaction regions in trapped particles. It is suggested that the 10-hour modulation of interplanetary Jovian electrons may be associated with the arrival at the dawn magnetopause of a rarefaction region each planetary rotation.     

Interferometric coupling of the Keck telescopes with single-mode fibers

Here we report successful interferometric coupling of two large telescopes with single-mode fibers. Interference fringes were obtained in the 2- to 2.3-micrometer wavelength range on the star 107 Herculis by using the two Keck 10-meter telescopes, each feeding their common interferometric focus with 300 meters of single-mode fibers. This experiment demonstrates the potential of fibers for future kilometric arrays of telescopes and is the first step toward the 'OHANA (Optical Hawaiian Array for Nanoradian Astronomy) interferometer at the Mauna Kea observatory in Hawaii. It opens the way to sensitive optical imagers with resolutions below 1 milli-arc second. Our experimental setup can be directly extended to large telescopes separated by many hundreds of meters.     

Ulysses radio and plasma wave observations in the jupiter environment

The Unified Radio and Plasma Wave (URAP) experiment has produced new observations of the Jupiter environment, owing to the unique capabilities of the instrument and the traversal of high Jovian latitudes. Broad-band continuum radio emission from Jupiter and in situ plasma waves have proved valuable in delineating the magnetospheric boundaries. Simultaneous measurements of electric and magnetic wave fields have yielded new evidence of whistler-mode radiation within the magnetosphere. Observations of aurorallike hiss provided evidence of a Jovian cusp. The source direction and polarization capabilities of URAP have demonstrated that the outer region of the lo plasma torus supported at least five separate radio sources that reoccurred during successive rotations with a measurable corotation lag. Thermal noise measurements of the lo torus densities yielded values in the densest portion that are similar to models suggested on the basis of Voyager observations of 13 years ago. The URAP measurements also suggest complex beaming and polarization characteristics of Jovian radio components. In addition, a new class of kilometer-wavelength striated Jovian bursts has been observed.     

Extreme ultraviolet observations from voyager 2 encounter with jupiter

Extreme ultraviolet spectral observations of the Jovian planetary system made during the Voyager 2 encounter have extended our knowledge of many of the phenomena and physical processes discovered by the Voyager 1 ultraviolet spectrometer. In the 4 months between encounters, the radiation from Io's plasma torus has increased in intensity by a factor of about 2. This change was accompanied by a decrease in plasma temperature of about 30 percent. The high-latitude auroral zones have been positively associated with the magnetic projection of the plasma torus onto the planet. Emission in molecular hydrogen bands has been detected from the equatorial regions of Jupiter, indicating planetwide electron precipitation. Hydrogen Lyman alpha from the dark side of the planet has been measured at an intensity of about 1 kilorayleigh. An observation of the occultation of alpha Leonis by Jupiter was carried out successfully and the data are being analyzed in detail.     

Magnetic field studies at jupiter by voyager 1: preliminary results

Results obtained by the Goddard Space Flight Center magnetometers on Voyager 1 are described. These results concern the large-scale configuration of the Jovian bow shock and magnetopause, and the magnetic field in both the inner and outer magnetosphere. There is evidence that a magnetic tail extending away from the planet on the nightside is formed by the solar wind-Jovian field interaction. This is much like Earth's magnetosphere but is a new configuration for Jupiter's magnetosphere not previously considered from earlier Pioneer data. We report on the analysis and interpretation of magnetic field perturbations associated with intense electrical currents (approximately 5 x 10(6) amperes) flowing near or in the magnetic flux tube linking Jupiter with the satellite Jo and induced by the relative motion between Io and the corotating Jovian magnetosphere. These currents may be an important source of heating the ionosphere and interior of Io through Joule dissipation.     

Infrared observations of the saturnian system from voyager 2

During the passage of Voyager 2 through the Saturn system, infrared spectral and radiometric data were obtained for Saturn, Titan, Enceladus, Tethys, Iapetus, and the rings. Combined Voyager 1 and Voyager 2 observations of temperatures in the upper troposphere of Saturn indicate a seasonal asymmetry between the northern and southern hemispheres, with superposed small-scale meridional gradients. Comparison of high spatial resolution data from the two hemispheres poleward of 60 degrees latitude suggests an approximate symmetry in the small-scale structure, consistent with the extension of a symmetric system of zonal jets into the polar regions. Longitudinal variations of 1 to 2 K are observed. Disk- averaged infrared spectra of Titan show little change over the 9-month interval between Voyager encounters. By combining Voyager 2 temperature measurements with ground-based geometric albedo determinations, phase integrals of 0.91 +/- 0.13 and 0.89 +/- 0.09 were derived for Tethys and Enceladus, respectively. The subsolar point temperature of dark material on Iapetus must exceed 110 K. Temperatures (and infrared optical depths) for the A and C rings and for the Cassini division are 69 +/- 1 K (0.40 +/- 0.05), 85 +/- 1 K (0.10 +/- 0.03), and 85 +/- 2 K (0.07 +/- 0.04), respectively.     

A carbonate-rich, hydrated, interplanetary dust particle: possible residue from protostellar clouds

Transmission electron microscopy of a hydrated interplanetary dust particle (IDP) indicates that it contains abundant magnesium-iron carbonates, primarily breunnerite and magnesian siderite. This IDP displays a strong absorption band at 6.8 micrometers in its infrared spectrum, similar to that in certain protostellar spectra. The carbonates probably account for the 6.8-micrometer band in the IDP spectrum, suggesting that carbonate also may occur in interstellar dust and be the source of the controversial 6.8-micrometer feature from the protostellar spectra.     

Magnetic field studies at jupiter by voyager 2: preliminary results

Data from the Goddard Space Flight Center magnetometers on Voyager 2 have yielded on inbound trajectory observations of multiple crossings of the bow shock and magnetosphere near the Jupiter-sun line at radial distances of 99 to 66 Jupiter radii (RJ) and 72 to 62 RJ, respectively. While outbound at a local hour angle of 0300, these distances increase appreciably so that at the time of writing only the magnetopause has been observed between 160 and 185 RJ. These results and the magnetic field geometry confirm the earlier conclusion from Voyager I studies that Jupiter has an enormous magnetic tail, approximately 300 to 400 RJ in diameter, trailing behind the planet with respect to the supersonic flow of the solar wind. Addi- tional observations of the distortion of the inner magnetosphere by a concentrated plasma show a spatial merging of the equatorial magnetodisk current with the cur- rent sheet in the magnetic tail. The spacecraft passed within 62,000 kilometers of Ganymede (radius = 2,635 kilometers) and observed characteristic fluctuations in- terpreted tentatively as being due to disturbances arising from the interaction of the Jovian magnetosphere with Ganymede.     

The sand seas of Titan: Cassini RADAR observations of longitudinal dunes

The most recent Cassini RADAR images of Titan show widespread regions (up to 1500 kilometers by 200 kilometers) of near-parallel radar-dark linear features that appear to be seas of longitudinal dunes similar to those seen in the Namib desert on Earth. The Ku-band (2.17-centimeter wavelength) images show approximately 100-meter ridges consistent with duneforms and reveal flow interactions with underlying hills. The distribution and orientation of the dunes support a model of fluctuating surface winds of approximately 0.5 meter per second resulting from the combination of an eastward flow with a variable tidal wind. The existence of dunes also requires geological processes that create sand-sized (100- to 300-micrometer) particulates and a lack of persistent equatorial surface liquids to act as sand traps.     

Voyager detection of nonthermal radio emission from saturn

The planetary radio astronomy experiment on board the Voyager spacecraft has detected bursts of nonthermal radio noise from Saturn occurring near 200 kilohertz, with a peak flux density comparable to higher frequency Jovian emissions. The radiation is right-hand polarized and is most likely emitted in the extraordinary magnetoionic mode from Saturn's northern hemisphere. Modulation that is consistent with a planetary rotation period of 10 hours 39.9 minutes is apparent in the data.     

The hot plasma environment at jupiter: ulysses results

Measurements of the hot plasma environment during the Ulysses flyby of Jupiter have revealed several new discoveries related to this large rotating astrophysical system. The Jovian magnetosphere was found by Ulysses to be very extended, with the day-side magnetopause located at approximately 105 Jupiter radii. The heavy ion (sulfur, oxygen, and sodium) population in the day-side magnetosphere increased sharply at approximately 86 Jupiter radii. This is somewhat more extended than the "inner" magnetosphere boundary region identified by the Voyager hot plasma measurements. In the day-side magnetosphere, the ion fluxes have the anisotropy direction expected for corotation with the planet, with the magnitude of the anisotropy increasing when the spacecraft becomes more immersed in the hot plasma sheet. The relative abundances of sulfur, oxygen, and sodium to helium decreased somewhat with decreasing radial distance from the planet on the day-side, which suggests that the abundances of the Jupiter-derived species are dependent on latitude. In the dusk-side, high-latitude region, intense fluxes of counter-streaming ions and electrons were discovered from the edge of the plasma sheet to the dusk-side magnetopause. These beams of electrons and ions were found to be very tightly aligned with the magnetic field and to be superimposed on a time- and space-variable isotropic hot plasma background. The currents carried by the measured hot plasma particles are typically approximately 1.6 x 10(-4) microamperes per square meter or approximately 8 x 10(5) amperes per squared Jupiter radius throughout the high-latitude magnetosphere volume. It is likely that the intense particle beams discovered at high Jovian latitudes produce auroras in the polar caps of the planet.     

Magnetic field studies by voyager 1: preliminary results at saturn

Magnetic field studies by Voyager 1 have confirmed and refined certain general features of the Saturnian magnetosphere and planetary magnetic field established by Pioneer 11 in 1979. The main field of Saturn is well represented by a dipole of moment 0.21 +/- 0.005 gauss-R(s)(3) (where 1 Saturn radius, R(s), is 60,330 kilometers), tilted 0.7 degrees +/- 0.35 degrees from the rotation axis and located within 0.02 R(s) of the center of the planet. The radius of the magnetopause at the subsolar point was observed to be 23 R(s) on the average, rather than 17 R(s). Voyager 1 discovered a magnetic tail of Saturn with a diameter of approximately 80 R(s). This tail extends away from the Sun and is similar to type II comet tails and the terrestrial and Jovian magnetic tails. Data from the very close flyby at Titan (located within the Saturnian magnetosphere) at a local time of 1330, showed an absence of any substantial intrinsic satellite magnetic field. However, the results did indicate a very well developed, induced magnetosphere with a bipolar magnetic tail. The upper limit to any possible internal satellite magnetic moment is 5 x 10(21) gauss-cubic centimeter, equivalent to a 30-nanotesla equatorial surface field.     

Transparent, conductive carbon nanotube films

We describe a simple process for the fabrication of ultrathin, transparent, optically homogeneous, electrically conducting films of pure single-walled carbon nanotubes and the transfer of those films to various substrates. For equivalent sheet resistance, the films exhibit optical transmittance comparable to that of commercial indium tin oxide in the visible spectrum, but far superior transmittance in the technologically relevant 2- to 5-micrometer infrared spectral band. These characteristics indicate broad applicability of the films for electrical coupling in photonic devices. In an example application, the films are used to construct an electric field-activated optical modulator, which constitutes an optical analog to the nanotube-based field effect transistor.