Uranian ring orbits from earth-based and Voyager occultation observations

French, R. G.; Elliot, J. L.; French, Linda M.; Kangas, Julie A.; Meech, К. J.; Ressler, Michael E.; Buie, M. W.; Frogel, J. A.; Holberg, J. B.; Fuensalida, J. J.; Joy, M.

doi:10.1016/0019-1035(88)90104-2

Cited by 69 publications

(31 citation statements)

References 19 publications

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“…Subsequently, Murray & Thompson (1990) noted that this resonance needs to be re-examined using updated satellite parameters. At the time, with a smaller data set, there was no detection of either an m = 3 or an m = 13 mode in the η ring, nor any other modes due to resonances with known satellites having observed effects on any of the other previously noted rings' edges (French et al 1988). Thus, it was only sensible to dismiss these resonances, and it is reasonable that they have not been of interest since.…”

Section: Introductionmentioning

confidence: 79%

“…Longitudes are measured in the prograde direction from the ascending node of Uranus' equator on the Earth's equator of the J2000 epoch. French et al (1988) have included all observations from 1977-1986 in their most recent fit, but more recent observations are unpublished. Note-The precise numbers for the ring's position are derived from an analysis of the entire Uranian ring data set, including re-determined pole position, GM , J2, J4, and time offsets.…”

Section: Appendixmentioning

confidence: 99%

“…Since then, the Uranian rings have been studied extensively with ground based stellar occultations (Millis & Wasserman 1978;Nicholson et al 1978;Elliot et al 1981b,a;Nicholson et al 1981;French et al 1982;Sicardy et al 1982;Elliot et al 1983French et al 1986b,a;Elliot et al 1987;French et al 1988French et al , 1996. Occultations provide very precise radial locations of the rings at different longitudes in their orbits around Uranus.…”

Section: Introductionmentioning

confidence: 99%

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Weighing Uranus’ Moon Cressida with the η Ring

Chancia

Hedman

French

2017

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The η ring is one of the narrow rings of Uranus, consisting of a dense core that is 1-2 km wide and a diffuse outer sheet spanning about 40 km. Its dense core lies just exterior to the 3:2 Inner Lindblad Resonance of the small moon Cressida. We fit the η ring radius residuals and longitudes from a complete set of both ground-based and Voyager stellar and radio occultations of the Uranian rings spanning 1977-2002. We find variations in the radial position of the η ring that are likely generated by this resonance, and take the form of a 3-lobed structure rotating at an angular rate equal to the mean motion of the moon Cressida. The amplitude of these radial oscillations is 0.667±0.113 km, which is consistent with the expected shape due to the perturbations from Cressida. The magnitude of these variations provides the first measurement of the mass and density of the moon Cressida (m = 2.5 ± 0.4 × 10 17 kg and ρ = 0.86 ± 0.16 g/cm 3 ) or, indeed, any of Uranus' small inner moons. A better grasp of inner Uranian satellite masses will provide another clue to the composition, dynamical stability, and history of Uranus' tightly packed system of small moons.

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Section: Introductionmentioning

confidence: 79%

Section: Appendixmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Weighing Uranus’ Moon Cressida with the η Ring

Chancia

Hedman

French

2017

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“…The refractivity at STP at 8900Å for this mixture is 1.215 × 10 −4 Huang 1977, Mansfield andPeck 1969). The effective gravity, g, was computed using G M = 5,793,939 km 3 s −2 (Tyler et al 1986), harmonic coefficients defined at R = 26,200 km of J 2 = 3.34343 × 10 −3 and J 4 = −2.885 × 10 −5 (French et al 1988), and a rotation period at the 1 µbar level of 17.7 hr derived from Uranus' oblateness by Baron et al (1989), yielding g = 8.48 and 8.52 m s −2 for immersion and emersion, respectively. Because a primary goal of this analysis is the comparison with previous observations, no attempt was made to account for the vertical variation of gravity or molecular weight.…”

Section: Discussionmentioning

confidence: 99%

Uranus after Solstice: Results from the 1998 November 6 Occultation

Young

Bosh

Elliot

et al. 2001

Icarus

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We observed a stellar occultation of the star U149 by Uranus from Lowell Observatory and the IRTF on Mauna Kea on November 6, 1998. The temperatures derived from isothermal fits to the Lowell lightcurves are 116.7 ± 7.9 K for immersion, and 124.8 ± 15.5 K for emersion. The secular increase in temperature seen during the period 1977-1983 has reversed. Furthermore, the rate of decrease (≥1.2 K/yr) cannot be explained solely by radiative cooling. Although the temperature structure of Uranus' upper atmosphere may be related to seasonal effects (e.g., the subsolar latitude) or local conditions (e.g., diurnally averaged insolation), these observations suggest nonradiative influences on the temperature, such as adiabatic heating/cooling or thermal conduction.

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“…• (French et al 1988). Various theories have been proposed to explain the overall architecture of this ring system, which are best summarized in Elliot & Nicholson (1984) and French et al (1991).…”

Section: Introductionmentioning

confidence: 99%

Are There Moonlets Near the Uranian Α and Β Rings?

Chancia¹,

Hedman²

2016

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The Voyager 2 Radio Science Subsystem occultations of the Uranian α and β rings exhibit quasiperiodic optical depth variations with radial wavelengths that vary with longitude. These patterns may be wakes from small moonlets orbiting exterior to these rings. Based on the observed structures in the rings, we estimate that the moonlets would need to be located ∼ 100 km exterior to the rings' semimajor axes (106 +22 −12 km for α and 77 +8 −4 km for β) and be 2 − 7 km in radius. Such moonlets could help keep the rings confined. Due to their small radii and presumed low albedo, the expected brightness of these moonlets is on the order of the noise in Voyager 2 images.

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Uranian ring orbits from earth-based and Voyager occultation observations

Cited by 69 publications

References 19 publications

Weighing Uranus’ Moon Cressida with the η Ring

Weighing Uranus’ Moon Cressida with the η Ring

Uranus after Solstice: Results from the 1998 November 6 Occultation

Are There Moonlets Near the Uranian Α and Β Rings?

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