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New Observational Results Concerning Jupiter's Great Red Spot
Achterberg, Richard K.; Flasar, F. Michael; Simon-Miller, Amy A. +4 more
The changing size and aspect ratio of the Great Red Spot from 1880 to 2000 are reviewed, indicating that the length of the system has decreased significantly over the last 100 years and continues to decrease at present at a rate of 0.19 degrees per year. Voyager IRIS maps of para hydrogen fraction and potential temperature over the system are pres…
Saturn's F Ring: Kinematics and Particle Sizes from Stellar Occultation Studies
Nicholson, P. D.; Bosh, A. S.; Olkin, C. B. +1 more
The occultation of GSC5249-01240 by Saturn's rings was observed in a spectrally resolved mode using the Faint Object Spectrograph on the Hubble Space Telescope. By combining these data with other occultation data, we have determined the inclination of the F ring to be 0.0065±0.0014 deg. Our inclined F ring orbit model explains an abrupt decrease i…
The Nucleus of Comet 22P/Kopff and Its Inner Coma
Jorda, L.; Lamy, P. L.; A'Hearn, M. F. +3 more
We report the detection of the nucleus of Comet 22P/Kopff with the Planetary Camera of the Hubble Space Telescope (HST) and with the Infrared Camera of the Infrared Space Observatory (ISOCAM). The HST observations were performed on 18 July 1996, 16 days after its perihelion passage of 2 July 1996, when it was at Rh=1.59 AU from the Sun …
HST Multicolor (255-1042 nm) Photometry of Saturn's Main Rings. I: Radial Profiles, Phase and Opening Angle Variations, and Regional Spectra
French, Richard G.; Dones, Luke; Cuzzi, Jeffrey N.
The main rings of Saturn were observed with the Planetary Camera of the WFPC2 instrument on the Hubble Space Telescope (HST) from September 1996 to December 2000 as the ring opening angle to Earth and Sun increased from 4° to 24°, with a spread of phase angles between 0.3° and 6° at each opening angle. The rings were routinely observed in the five…
A Study of Saturn's Ring Phase Curves from HST Observations
Poulet, F.; French, R. G.; Dones, L. +1 more
Solar phase curves between 0.3° and 6.0° and color ratios at wavelengths λ=0.336 µm and λ=0.555 µm for Saturn's rings are presented using recent Hubble Space Telescope observations. We test the hypothesis that the phase reddening of the rings is less due to collective properties of the ring particles than to the individual properties o…
Spatial and Compositional Constraints on Non-ice Components and H 2O on Pluto's Surface
Buie, M. W.; Grundy, W. M.
We present four new near-infrared spectra of Pluto, measured separately from its satellite Charon during four HST/NICMOS observations in 1998, timed to sample four evenly spaced longitudes on Pluto. Being free of contamination by telluric absorptions or by Charon light, the new data are particularly valuable for studies of Pluto's continuum absorp…
Jupiter's Cloud Structure as Constrained by Galileo Probe and HST Observations
Sromovsky, L. A.; Fry, P. M.
The Galileo Probe sampled Jupiter's atmosphere at the edge of a 5-µm hot spot, where it found very little cloud opacity above the 700 mb level. Only τ=1-2 at λ=0.5 µm was inferred from Net Flux Radiometer observations (Sromovsky et al. 1998, J. Geophys. Res.103, 22,929-22,977), in seeming conflict with Chanover et al. (1997, Icarus128,…
Keck Adaptive Optics Images of Uranus and Its Rings
de Pater, Imke; Roe, H. G.; Max, C. E. +3 more
We present adaptive optic images of Uranus obtained with the 10-m W. M. Keck II telescope in June 2000, at wavelengths between 1 and 2.4 µm. The angular resolution of the images is ∼0.06-0.09″. We identified eight small cloud features on Uranus's disk, four of which were in the northern hemisphere. The latter features are ∼1000-2000 km in ex…
Methane Abundance on Titan, Measured by the Space Telescope Imaging Spectrograph
Lorenz, Ralph D.; Lemmon, Mark T.; Smith, Peter H.
Although methane is the dominant absorber in Titan's reflection spectrum, the amount of methane in the atmosphere has only been determined to an order of magnitude. We analyzed spectra from the Space Telescope Imaging Spectrograph, looking at both a bright surface region (700-km radius) and a dark surface region. The difference between the spectra…
A Comparative Study of Jovian Anticyclone Properties from a Six-Year (1994-2000) Survey
Colas, F.; Lecacheux, J.; Morales-Juberías, Raúl +1 more
We have used the Hubble Space Telescope archived images of Jupiter for the period 1994-2000, complemented by ground-based telescopic observations, to study in detail the long-term properties of synoptic-scale anticyclonic vortices (size > 1500 km, lifetime > months). We have also analyzed a set of Voyager 1 and 2 images obtained in 1979 to c…