Keck near-infrared observations of Saturn's E and G rings during Earth's ring plane crossing in August 1995

Pater, Imke de; Martin, S. C.; Showalter, M. R.

doi:10.1016/j.icarus.2004.07.012

Cited by 44 publications

(41 citation statements)

References 21 publications

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“…In such a profile, the signal at a given radius r 0 includes contributions from material at all radii r > r 0 . However, these projection effects can be removed using an onion-peeling algorithm, which iteratively estimates the signal at each radius and removes that material's contribution from the rest of the data (Showalter 1985;Showalter et al 1987;de Pater et al 2004;Hedman et al 2012). When properly normalized, this algorithm yields a profile of the ring's normal I/F that can be directly compared with the data obtained at higher elevation angles.…”

Section: From Images To Radial Profilesmentioning

confidence: 99%

Saturn’s G and D Rings Provide Nearly Complete Measured Scattering Phase Functions of Nearby Debris Disks

Hedman

Stark

2015

ApJ

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The appearance of debris disks around distant stars depends upon the scattering/phase function (SPF) of the material in the disk. However, characterizing the SPFs of these extrasolar debris disks is challenging because only a limited range of scattering angles are visible to Earth-based observers. By contrast, Saturn's tenuous rings can be observed over a much broader range of geometries, so their SPFs can be much better constrained. Since these rings are composed of small particles released from the surfaces of larger bodies, they are reasonable analogs to debris disks and so their SPFs can provide insights into the plausible scattering properties of debris disks. This work examines two of Saturn's dusty rings: the G ring (at 167,500 km from Saturn's center) and the D68 ringlet (at 67,600 km). Using data from the cameras onboard the Cassini spacecraft, we are able to estimate the rings' brightnesses at scattering angles ranging from 170• to 0.5 • . We find that both of the rings exhibit extremely strong forwardscattering peaks, but for scattering angles above 60• their brightnesses are nearly constant. These SPFs can be well approximated by a linear combination of three Henyey-Greenstein functions, and are roughly consistent with the SPFs of irregular particles from laboratory measurements. Comparing these data to Fraunhofer and Mie models highlights several challenges involved in extracting information about particle compositions and size distributions from SPFs alone. The SPFs of these rings also indicate that the degree of forward scattering in debris disks may be greatly underestimated.

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Section: From Images To Radial Profilesmentioning

confidence: 99%

Saturn’s G and D Rings Provide Nearly Complete Measured Scattering Phase Functions of Nearby Debris Disks

Hedman

Stark

2015

ApJ

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“…The icy moon Enceladus was proposed early as the dominant source of ring particles since the edge-on brightness profile peaks near the moon's mean orbital distance. For the same reason, Tethys was identified as a secondary E ring particle source by de Pater et al (2004). Photometrical models propose that for micron-sized grains the peak optical depth is τ ∼ 1.6x10 −5 corresponding to about 180 grains per square centimeter (Showalter, Cuzzi, & Larson, 1991).…”

Section: G Ring Encounter On Day 248mentioning

confidence: 99%

“…Photometrical models propose that for micron-sized grains the peak optical depth is τ ∼ 1.6x10 −5 corresponding to about 180 grains per square centimeter (Showalter, Cuzzi, & Larson, 1991). The vertical profile of the ring was investigated by De Pater et al (2004) by Earth-bound infrared observations in 1995. The results showed a fullwidth-half-maximum (FWHM) based on grain sizes dominating the optical cross section of about 9.000 km between the Mimas and the Enceladus orbit, and a minimum of 8.000 km at the distance of Enceladus.…”

Section: G Ring Encounter On Day 248mentioning

confidence: 99%

The cosmic dust analyser onboard cassini: ten years of discoveries

et al. 2011

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“…Because Jupiter's rings are optically thin, edge-on, and presumably cylindrically symmetric, we can invert the images by using an "onion-peel" deconvolution method (Showalter et al 1987;dP99;de Pater et al 2004a;Verbanac et al 2005). We assume that each row in the image represents an edge-on radial profile of the rings.…”

Section: "Onion-peeling" and The Radial Distribution Of The Ringsmentioning

confidence: 99%

Keck observations of the 2002–2003 jovian ring plane crossing

Pater¹,

Showalter²,

Macintosh³

2008

Icarus

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We present new observations of Jupiter's ring system at a wavelength of 2.2 µm obtained with the 10-m W. M. Keck telescopes on three nights during a ring plane crossing: UT 19 December 2002, and 22 and 26 January 2003. We used conventional imaging, plus adaptive optics on the last night. Here we present detailed radial profiles of the main ring, halo and gossamer rings, and interpret the data together with information extracted from radio observations of Jupiter's synchrotron radiation. The main ring is confined to a 800-km-wide annulus between 128,200 and 129,000 km, with a ∼ 5000 km extension on the inside. The normal optical depth is 8 × 10 −6 , 15% of which is provided by bodies with radii a > ∼ 5 cm. These bodies are as red as Metis. Half the optical depth, τ ≈ 4 × 10 −6 , is attributed to micron-sized dust, and the remaining τ ≈ 3 × 10 −6 to grains tens to hundreds of µm in size. The inward extension consists of micron-sized (a < ∼ 10 µm ) dust, which probably migrates inward under Poynting-Robertson drag. The inner limit of this extension falls near the 3:2 Lorentz resonance (at orbital radius r = 122, 400 km), and coincides with the outer limit of the halo. The gossamer rings appear to be radially confined, rather than broad sheets of material. The Amalthea ring is triangularly shaped, with a steep outer dropoff over ∼5000 km, extending a few 1000 km beyond the orbit of Amalthea, and a more gradual inner dropoff over 15,000-20,000 km. The inner edge is near the location of the synchronous orbit. The optical depth in the Amalthea ring is ∼ 5×10 −7 , up to 20% of which is comprised of macroscopic material. The optical depth in the Thebe ring is a factor of 3 smaller.

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Keck near-infrared observations of Saturn's E and G rings during Earth's ring plane crossing in August 1995

Cited by 44 publications

References 21 publications

Saturn’s G and D Rings Provide Nearly Complete Measured Scattering Phase Functions of Nearby Debris Disks

Saturn’s G and D Rings Provide Nearly Complete Measured Scattering Phase Functions of Nearby Debris Disks

The cosmic dust analyser onboard cassini: ten years of discoveries

Keck observations of the 2002–2003 jovian ring plane crossing

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