A Study of Saturn's Ring Phase Curves from HST Observations

Poulet, F.; Cuzzi, J. N.; French, R. G.; Dones, L.

doi:10.1006/icar.2002.6852

Cited by 42 publications

(56 citation statements)

References 47 publications

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“…• of phase angle (Poulet et al 2002a), our data show that only slight variations in the spectra are seen in response to differing solar phase angles for λ between 0.9 and 2.6 µm, except between 1.1 and 1.4 µm where the 0.6…”

Section: The Spectramentioning

confidence: 57%

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Compositions of Saturn's rings A, B, and C from high resolution near-infrared spectroscopic observations

Poulet

Cruikshank

Cuzzi

et al. 2003

A&A

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Abstract. We used the NASA IRTF spectrograph SpeX to obtain near-infrared spectra (0.9-5.4 µm) of Saturn's rings, achieving spectral resolution λ/∆λ of about 2000. The spatial resolution (about 1 arcsec) is sufficient to distinguish the three main ring components (A, B and C rings) from one another. These new observations of Saturn's rings are the first to combine an extended spectral range with high spectral resolution and good spatial resolution. We combined these data with recent photometric observations acquired by HST in the 0.3-1.0 µm range. The spectra of the A band B rings are dominated by strong features due to crystalline water ice. The shape and the depth of these absorptions differ for each ring, which indicates different water ice grain sizes and abundances. No spectral evidence for volatile ices other than water ice has been detected. Both the lower albedo and the less blue slope in the near-infrared reflectance of the C ring indicate a concentration of dark material different from that in the A and B rings. The broader triangular Fresnel reflection peak at 3.1 µm may support the presence of some amount of amorphous ice. The C ring spectrum exhibits bands centered at 1.73 and 3.4 µm which agree in position quite well with the C-H bands. Although the detection is probable, it requires confirmation. With a radiative transfer model, we constrain the grain sizes and the relative abundances of water ice, a dark colorless component (amorphous carbon) to adjust the albedo and a second contaminant to reproduce the reddening in the UV-visible range represented here by organic tholins. The dark component of the C ring spectrum is included as an intra-mixture only. The cosmogenic implications of the inferred compositions are discussed.

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Section: The Spectramentioning

confidence: 57%

“…Cuzzi et al (2002) and Poulet et al (2002a) show how the wavelength-dependent reflectivity in the UV-visible range can significantly vary with phase even over 0-6…”

Section: Introductionmentioning

confidence: 99%

Compositions of Saturn's rings A, B, and C from high resolution near-infrared spectroscopic observations

Poulet

Cruikshank

Cuzzi

et al. 2003

A&A

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“…2. We ignore all angle dependences of reflectance, which can affect the spectrum to some degree (Cuzzi et al 2002, Poulet et al 2002a.…”

Section: A Composite Spectrummentioning

confidence: 99%

“…The light scattering at wavelength λ from a particulate surface of a material with real and imaginary parts of the refractive index n and k is described by two parameters: (1) the ray propagation between scattering points, characterized by the optical depth τ = 4πkl/λ, where the parameter l is the average length of light propagation in a particle between internal reflections (for transparent particles, l should be equal approximately to the average diameter of the particle), and (2) the coefficient P, which is the porosity of a regolith-covered surface. We take a value of P = 0.9, which should be typical for the regolith of Saturn's ring particles (Poulet et al 2002a); in any case, Shkuratov et al (1999) showed that the porosity does not significantly affect the albedo of bright particulate surfaces. Shkuratov et al (1999) considered two types of particulate mixtures.…”

Section: Choice Of the Scattering Modelmentioning

confidence: 99%

The Composition of Saturn's Rings

Poulet

Cuzzi

2002

Icarus

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“…Two causes to give rise to the opposition effect are usually considered: (1) shadow-hiding and (2) interference-enhancement, often called coherent-backscatter. Some general regolith properties-dependent characteristics of each mechanism are understood, and some papers are devoted to a discussion on the relative contribution of both mechanisms (Drossart 1993;Helfenstein et al 1997Helfenstein et al , 1998Hapke et al 1998;Nelson et al 2000;Belskaya & Shevchenko 2000;Shkuratov & Helfenstein 2001;Poulet et al 2002). One can check for the effect of coherent backscatter and/or shadow hiding by studying the influence of wavelength of incident light on the opposition brigthening.…”

Section: Introductionmentioning

confidence: 99%

Photometry of the Kuiper-Belt object 1999 TD$_{\sf\sl 10}$ at different phase angles

Rousselot

Petit

Poulet

et al. 2003

A&A

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Abstract. We present photometric observations of the Kuiper-Belt object 1999 TD 10 at different phase angles and for three different broad band filters (B, V and R). This object was observed with the Danish 1.54-m telescope of ESO in Chile during six different observing nights corresponding to a phase angle of 0. 30, 0.37, 0.92, 3.43, 3.48 and 3.66 • . Extra observations were obtained in September 2002 with the VLT UT1/FORS1 combination to confirm that 1999 TD 10 does not exhibit any cometary activity, and in October 2001 with the Sierra Nevada Observatory 1.50-m telescope in order to add relative magnitudes to improve the determination of the rotation period. The observations are compatible with a single-peaked rotational lightcurve with a 7h41.5min ± 0.1 min period or a doublepeaked lightcurve with a 15h22.9min ± 0.1 min period. If a single-peaked rotational lightcurve is assumed the amplitude is 0.51 ± 0.03, 0.49 ± 0.05 and 0.60 ± 0.09 mag for the R, V and B bands, respectively. We present the phase curve obtained when assuming that the lightcurve is single-peaked. This phase curve reveals clearly an increase of about 0.3 mag and of similar importance for the three bands when phase angle decreases from 3.7 • to 0.3 • . The phase curve reveals a linear increase of the brightness with the decreasing phase angle and, consequently, does not permit a modeling of the opposition surge. Neverthless the poor repartition of the observational data does not permit a firm conclusion concerning the presence or absence of an opposition surge on the phase angle range covered by our data. Complementary observations are needed.

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A Study of Saturn's Ring Phase Curves from HST Observations

Cited by 42 publications

References 47 publications

Compositions of Saturn's rings A, B, and C from high resolution near-infrared spectroscopic observations

Compositions of Saturn's rings A, B, and C from high resolution near-infrared spectroscopic observations

The Composition of Saturn's Rings

Photometry of the Kuiper-Belt object 1999 TD$_{\sf\sl 10}$ at different phase angles

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