Keck Adaptive Optics Images of Uranus and Its Rings

Pater, Imke de; Gibbard, S. G.; Macintosh, Bruce; Roe, H. G.; Gavel, Donald T.; Max, C. E.

doi:10.1006/icar.2002.6966

Cited by 33 publications

(23 citation statements)

References 33 publications

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“…The angular resolution was 0.05 , which corresponds to ∼1350 km at the center of Neptune's disk. We note that the actual angular resolution on Neptune may be slightly worse (∼0.06-0.07 ), as Neptune itself was used for wavefront sensing, and the AO system at that time had not yet been optimized to observe objects with a large angular size (see e.g., de Pater et al 2002de Pater et al , 2005van Dam et al 2004).…”

Section: Data Acquisition and Reductionmentioning

confidence: 99%

Neptune’s zonal winds from near-IR Keck adaptive optics imaging in August 2001

Martin

Pater

Marcus

2011

Astrophys Space Sci

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We present H-band (1.4-1.8 µm) images of Neptune with a spatial resolution of ∼0.06 , taken with the W.M. Keck II telescope using the slit-viewing camera (SCAM) of the NIRSPEC instrument backed with Adaptive Optics. Images with 60-second integration times span 4 hours each on UT 20 and 21 August, 2001 and ∼1 hour on UT 1 September, 2001. These images were used to characterize the overall brightness distribution on Neptune, and to determine rotations periods (which translate into wind speeds) of individual cloud features.The images show that the spatial brightness distribution of cloud features, in particular the bright bands at midsouthern latitudes and near 30°N, changed considerably between 1989 (Voyager era) and 2001. The brightest features extend latitudinally over several degrees, and despite the different velocities in different latitude bands, these bright features remain coherent. We show that these features are bright in part because of the foreshortening effect near the limb, which suggests that the features may be composed of small bright clouds that happen to line up near the limb.At certain latitudes (mid-southern and northern latitudes), there is considerable dispersion in relative rotation periods (and hence zonal velocities) of faint and moderately

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Section: Data Acquisition and Reductionmentioning

confidence: 99%

Neptune’s zonal winds from near-IR Keck adaptive optics imaging in August 2001

Martin

Pater

Marcus

2011

Astrophys Space Sci

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“…de Pater et al (2002) presented Keck adaptive optics (AO) observations of the uranian system, which were taken soon after the AO system became a facility instrument. Since their field of view was 4.5 , they mosaicked Uranus to form a complete picture of the planet and its rings.…”

Section: Introductionmentioning

confidence: 99%

Near-infrared adaptive optics imaging of the satellites and individual rings of Uranus

Gibbard¹,

Pater²,

Hammel³

2005

Icarus

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We present the first Earth-based images of several of the individual faint rings of Uranus, as observed with the adaptive optics system on the W.M. Keck II telescope on four consecutive days in October 2003. We derive reflectivities based on multiple measurements of 8 minor moons of Uranus as well as Ariel and Miranda in filters centered at wavelengths of 1.25(J), 1.63(H), and 2.1(Kp) µm. These observations have a phase angle of 1.84 • -1.96 • . We find that the small satellites are somewhat less bright than in observations made by the HST at smaller phase angles, confirming an opposition surge effect. We calculate albedoes for the ring groups and for each ring separately. We find that the ring particles, as well as the particles in the three other ring groups, have albedoes near 0.043 at these phase angles. The equivalent depths of some of the individual rings are different than predicted based upon ring widths from occultation measurements (assuming a constant particle ring brightness); in particular the γ ring is fainter and the η ring brighter than expected. Our results indicate that q, the ratio of ring intensity at apoapse vs. periapse, is close to 3.2 ± 0.16. This agrees well with a model that has a filling factor for the ring of 0.06 (Karkoschka, 2001, Icarus 151, 78-83). We also determine values of the north to south brightness ratio for the individual rings and find that in most cases they are close to unity.

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“…In the quadcell case, spot sizes changes lead to changes in slope estimate gain due to truncation of the spot on the detector. This has been observed in practice 6 and analyzed with an eye towards compensation.…”

Section: Lick Laser Guide Star Adaptive Opticsmentioning

confidence: 87%

Experimental results for correlation-based wavefront sensing

Poyneer¹,

Palmer²,

LaFortune³

et al. 2005

SPIE Proceedings

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Correlation wave-front sensing can improve Adaptive Optics (AO) system performance in two keys areas. For point-source-based AO systems, Correlation is more accurate, more robust to changing conditions and provides lower noise than a centroiding algorithm. Experimental results from the Lick AO system and the SSHCL laser AO system confirm this. For remote imaging, Correlation enables the use of extended objects for wave-front sensing. Results from short horizontal-path experiments will show algorithm properties and requirements.

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Keck Adaptive Optics Images of Uranus and Its Rings

Cited by 33 publications

References 33 publications

Neptune’s zonal winds from near-IR Keck adaptive optics imaging in August 2001

Neptune’s zonal winds from near-IR Keck adaptive optics imaging in August 2001

Near-infrared adaptive optics imaging of the satellites and individual rings of Uranus

Experimental results for correlation-based wavefront sensing

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