Saturn's Rings I Optical Depth Profiles from the 28 Sgr Occultation

Nicholson, P. D.; French, R. G.; Tollestrup, E. V.; Cuzzi, Jeffrey N.; Harrington, J.; Matthews, K.; Perkovic, Olga; Stover, R. J.

doi:10.1006/icar.2000.6356

Cited by 41 publications

(24 citation statements)

References 50 publications

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“…For example, the A and B rings of Saturn are inclined at $27 to the orbital plane, extend from 1.5 to 2.2 times Saturn's radius, and have optical depths greater than 0.4 over a wide range of wavelengths (Nicholson et al 2000). To a distant observer with a line of sight passing along the ecliptic, these two rings would cover an area similar to the planet itself.…”

Section: Summary and Discussionmentioning

confidence: 99%

Photometric Transits from the MACHO Project Database

Drake

Cook

2004

ApJ

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We have searched the MACHO project photometry database for light curves consistent with the transits of low-luminosity objects. By analyzing the 180,000 brightest stars in 14 0.5 deg 2 fields toward the Galactic bulge, we have found a few hundred low-amplitude eclipsing binary systems. We have used the shapes and colors of these objects to separate the transits of objects with relatively small radii from the grazing eclipses of stars with larger radii. We find nine objects with short-period eclipses consistent with either giant extrasolar planets or latetype dwarf stars.

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Section: Summary and Discussionmentioning

confidence: 99%

Photometric Transits from the MACHO Project Database

Drake

Cook

2004

ApJ

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“…Structurally, the rings appear to have changed little, if at all, since the Voyager observations in 1980/81 and the occultations by the star 28 Sagittarius (Sgr) in 1989 (Nicholson et al 2000). In the outer C ring, the familiar pattern of moderate optical depth "plateaux" is seen, and the only variable feature is the eccentric Maxwell ringlet (Porco et al 1984), which was sampled by VIMS close to pericenter at a radius of 87 477 ± 7 km.…”

Section: Ringsmentioning

confidence: 99%

Observations in the Saturn system during approach and orbital insertion, with Cassini's visual and infrared mapping spectrometer (VIMS)

Brown¹,

Baines

Bellucci³

et al. 2006

A&A

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The Visual and Infrared Mapping Spectrometer observed Phoebe, Iapetus, Titan and Saturn's rings during Cassini's approach and orbital insertion. Phoebe's surface contains water ice, CO 2 , and ferrous iron. Iapetus contains CO 2 and organic materials. Titan's atmosphere shows methane fluorescence, and night-side atmospheric emission that may be CO 2 and CH 3 D. As determined from cloud motions, the winds at altitude 25-30 km in the south polar region of Titan appear to be moving in a prograde direction at velocity ∼1 m s −1 . Circular albedo features on Titan's surface, seen at 2.02 µm, may be palimpsests remaining from the rheological adjustment of ancient impact craters. As such, their long-term persistence is of special interest in view of the expected precipitation of liquids and solids from the atmosphere. Saturn's rings have changed little in their radial structure since the Voyager flybys in the early 1980s. Spectral absorption bands tentatively attributed to Fe 2+ suggest that iron-bearing silicates are a source of contamination of the C ring and the Cassini Division.

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“…These profiles provide a measure of the role of wavelength-dependent resolution in ratios of the HST data. Also shown (lower solid curve) is the Voyager ISS normal optical depth profile obtained by the first author (see Dones et al 1993 andNicholson et al 2000), plotted against the right-hand scale. This data set, while incomplete in the outer A ring, more accurately represents the distribution of high optical depth material in the B ring than the more familiar Voyager PPS data set.…”

Section: Phase and Opening Angle Dependence Of Ring Reflectivitymentioning

confidence: 99%

“…The dashed region in the Voyager profile is contaminated by a spoke, which is more prominently dark in the G filter than the UV filter (the HST averages do not include spoke-contaminated regions). The radial optical depth profile at the bottom (right scale) is obtained from Voyager ISS data by JNC (for a discussion see Dones et al 1993or Nicholson et al 2000. It saturates at τ ≈ 2.5 due to loss of signal.…”

Section: Fig 12mentioning

confidence: 99%

HST Multicolor (255–1042 nm) Photometry of Saturn's Main Rings I: Radial Profiles, Phase and Opening Angle Variations, and Regional Spectra

Cuzzi

French

Dones

2002

Icarus

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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 HST wideband UBVRI filters (F336W, F439W, F555W, F675W, and F814W) and occasionally in the F255W, F785LP, and F1042M filters. The emphasis in this series of papers will be on radial color (implying compositional) variations. In this first paper we describe the analysis technique and calibration procedure, note revisions in a previously published Voyager ring color data analysis, and present new results based on over 100 HST images.In the 300-600 nm spectral range where the rings are red, the 555/336-nm ratio increases by about 14% as the phase angle increases from 0.3• to 6• . This effect, never reported previously for the rings, is significantly larger than the phase reddening which characterizes other icy objects, primarily because of the redness of the rings. However, there is no discernible tendency for color to vary with ring opening angle at a given phase angle, and there is no phase variation of color where the spectrum is flat. We infer from this combination of facts that multiple intraparticle scattering, either in a regolith or between facts of an unusually rough surface, is important in these geometries, but that multiple interparticle scattering in a vertically extended layer is not. Voyager color ratios at a phase angle of 14• are compatible with this trend, but calibration uncertainties prevent their use in quantitative modeling.Overall ring average spectra are compatible with those of earlier work within calibration uncertainties, but ring spectra vary noticeably with region. We refine and subdivide the regions previously defined by others. The variation seen between radial profiles of ratios between different wavelengths suggests the presence of multiple compositional components with different radial distributions. We present new radial profiles of far-UV color ratio (F336W/F255W) showing substantial global variations having a different radial structure than seen between 555 and 336 nm. We constrain radial variation in the strength of a putative 850-nm spectral feature to be at the percent level or less. There seem to be real variations in the shape of regional ring spectra between 800 and 1000 nm. c 2002 Elsevier Science (USA)

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Saturn's Rings I Optical Depth Profiles from the 28 Sgr Occultation

Cited by 41 publications

References 50 publications

Photometric Transits from the MACHO Project Database

Photometric Transits from the MACHO Project Database

Observations in the Saturn system during approach and orbital insertion, with Cassini's visual and infrared mapping spectrometer (VIMS)

HST Multicolor (255–1042 nm) Photometry of Saturn's Main Rings I: Radial Profiles, Phase and Opening Angle Variations, and Regional Spectra

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