Britt, D.

Buratti, B. J.

Hicks, M. D.

Hillier, J.

Soderblom, L.

English

Open Research Online

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsPhotometric modeling of a cometary nucleus: takingHapke modeling to the limitConference or Workshop ItemHow to cite:Buratti, B. J.; Hicks, M. D.; Soderblom, L.; Hillier, J. and Britt, D. (2002). Photometric modeling of acometary nucleus: taking Hapke modeling to the limit. In: Solar System Remote Sensing, 20-21 Sep 2002.For guidance on citations see FAQs.c© [not recorded]Version: [not recorded]Link(s) to article on publisher’s website:http://www.lpi.usra.edu/meetings/ssrs2002/pdf/4008.pdfCopyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.ukPHOTOMETRIC MODELING OF A COMETARY NUCLEUS: TAKING HAPKE MODELINGTO THE LIMIT. B. J. Buratti (JPL), M. D. Hicks (JPL), L. Soderblom (USGS), J. Hillier (GraysHarbor College), D. Britt (U. Tenn.)In the past two decades, photometric modelsdeveloped by Bruce Hapke have been fit to awide range of bodies in the Solar System: TheMoon, Mercury, several asteroids, and many icyand rocky satellites. These models have enabledcomparative descriptions of the physicalattributes of planetary surfaces, includingmacroscopic roughness, particle size and size-distribution, the single scattering albedo, and thecompaction state of the optically active portionof the regolith. One challenging type of body toobserve and model, a cometary nucleus, awaitedthe first space based mission to obtain imagesunobscured by coma.The NASA-JPL Deep Space 1 Mission (DS1)encountered the short-period Jupiter-familycomet 19/P Borrelly on September 22, 2001,about 8 days after perihelion. Prior to its closestapproach of 2171 km, the remote-sensingpackage on the spacecraft obtained 25 CCDimages of the comet, representing the first close-up, unobscured view of a comet's nucleus (1).At closest approach, corresponding to aresolution of 47 meters per pixel, the intensityof the coma was less than 1% of that of thenucleus. An unprecented range of high solarphase angles (52-89 degrees), viewinggeometries that are in general attainable onlywhen a comet is active, enabled the firstquantitative and disk-resolved modeling ofsurface photometric physical parameters.The geometric albedo of Borrelly is 0.029 ±0.006, comparable to the dark hemisphere ofIapetus, the lowest albedo C-type asteroids, andthe Uranian rings. The Bond albedo, 0.009 ±0.002, is lower than that of any Solar Systemobject measured. Such a low value mayenhance the heating of the nucleus andsublimation of volatiles, which in turn causesthe albedo to decrease even further. A map ofnormal reflectance of Borrelly shows variationsfar greater than those seen on asteroids. Thetwo main terrain types, smooth and mottled (2),exhibit mean normal reflectances of 0.03 and0.022.Borrelly's physical photometric parametersare typical of other small dark bodies. Thenucleus exhibits significant variations inmacroscopic roughness, with the oldest, darkestterrain being slightly smoother. This resultsuggests the infilling of low-lying areas withdust and particles that have not been able toleave the comet. The surface of the comet isbackscattering, but there are substantialvariations in the single particle phase function.One region scatters isotropically (like cometarydust), suggesting that its regolith is controlledby native dust rather than by meteoriticbombardment.Work performed at NASA's Jet PropulsionLaboratory, California Institute of Technology.(1) Soderblom, L. et al. (2002). Science 296,1087.(2) Britt, D. et al. (2002). LPSC Abstract 1686.Solar System Remote Sensing Symposium (2002) 4008.pdf

Photometric modeling of a cometary nucleus: taking Hapke modeling to the limit

http://oro.open.ac.uk/8752/1/Photometric_modeling_of_a_cometary_nucleus.pdf

Photometric modeling of a cometary nucleus: taking Hapke modeling to the limit

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