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| Titel |
10 years of mapping the icy saturnian satellites |
| VerfasserIn |
Thomas Roatsch, Elke Kersten, Klaus-Dieter Matz, Carolyn Porco |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250089601
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| Publikation (Nr.) |
 EGU/EGU2014-3807.pdf |
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| Zusammenfassung |
| 10 YEARS OF MAPPING THE ICY SATURNIAN SATELLITES. Th. Roatsch1, E. Kersten1, K.-D. Matz1, and C.C. Porco2, 1Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany, Thom-as.Roatsch@dlr.de, 2 CICLOPS, Space Science Institute, Boulder, CO.
Introduction:
The Cassini spacecraft started its tour through the Saturnian system in July 2004. The Imaging Science Subsystem onboard the orbiter con-sists of a high-resolution Narrow Angle Camera (NAC) with a focal length of 2000 mm and a Wide Angle Camera (WAC) with a focal length of 200 mm [1]. One of the main objectives of the Cassini mission is to investigate the icy Saturnian satellites. These satellites were imaged in many flybys during the no-minal mission between 2004 and 2008. The imaging campaign continued during the first extended mission (‘‘Equinox mission’’) between 2008 and 2010 and continues during the current second extended mission (‘‘Solstice mission’’). It is now possible to image also the Northern parts of the Icy satellites which were not illuminated during the nominal mission.
Mosaicking:
The image data processing chain con-sists of the same steps as described in [2]: radiometric calibration, geometric correction, map projection, and mosaicking. Spacecraft position and camera pointing data are available in the form of SPICE kernels (http://naif.jpl.nasa.gov). While the orbit information is sufficiently accurate to be used directly for mapping purposes, the pointing information must be corrected using limb fits (semi-controlled mosaics) or by photo-grammetric bundle adjustment (controlled mosaics).
The coordinate system adopted by the Cassini mis-sion for satellite mapping is the IAU ‘‘planetographic’’ system, consisting of planetographic latitude and posi-tive West longitude. The surface position of the prime meridian as defined by the IAU cartography working group [3] is defined by small craters. New values for the rotational parameter W0 which defines the location of the prime meridian at January 1, 2000 were calcula-ted based on the high-resolution mosaics to be consis-tent with this definition [4] and approved by the IAU [3].
Cartographic maps:
Three different quadrangle schemes were used for the generation of the maps and the atlases [5]:
• A synoptic map for making planet-wide maps on a single sheet was used for Phoebe [2].
• A quadrangle scheme with 15 tiles for Mercury-sized bodies and high-resolution imaging was used for Enceladus, Tethys, Dione, and Rhea.
• A quadrangle scheme with 3 tiles, a subdivision of the synoptic map was used for Mimas and Iapetus.
The individual maps and tiles were extracted from global mosaics and reprojected into the defined map projections. We added resolution maps and index maps for every individual tile of the atlas, showing the image resolution, the image numbers and the location of the images for every map, respectively.
The entire atlases are available to the public through the Imaging Team’s website: http://ciclops.org/maps. The map tiles are also archived as standard products in the Planetary Data System (PDS): http://pds.jpl.nasa.gov/.
Nomenclature:
The nomenclature proposed by the Cassini-ISS team was approved by the IAU (http://planetarynames.wr.usgs.gov/). By international agreement, the features must be named after people or locations in
• „Le Morte d’Arthur“ for Mimas
• „The Thousand Nights and a Night“ for Enceladus
• „The Odyssey of Homer“ for Tethys
• „The Aeneid of Virgil“ for Dione
• Creation myths (with Asian emphasis) for Rhea
• „The Song of Roland“ for Iapetus
• “The Argonautica” for Phoebe
Future work:
The Cassini Equinox mission ended in 2010. Cassini is now operating in the Solstice mission hopefully until September 2017. Several additional close satellite flybys are scheduled for this time frame e.g. for Enceladus in October 2015 and for Mimas in January 2017. These upcoming flybys will help to replace the low-resolution parts of these atlases with higher resolu-tion images. The northern polar regions will be illumi-nated during the extended mission providing an oppor-tunity to obtain high-resolution Cassini coverage of high northern latitudes.
References:
[1] Porco et al., 2004, Cassini imaging science: instrument characteristics and anticipated scientific investigations at saturn, Space Science Re-view 115, 363–497. [2] Roatsch et al., 2006, Mapping of the icy Saturnian satellites: first results from Cassi-ni-ISS, Planetary Space Sciences 54, 1137–1145. [3] Archinal et al., 2011, Report of the IAU working group on cartographic coordinates and rotational elements: 2009. Celestial Mechanics and Dynamical Astronomy 109, 101–135. [4] Roatsch et al., 2009, Cartographic mapping of the icy satellites using ISS and VIMS data. In: Dougherty, M.K., Esposito, L.W., Krimigis, S.M. (Eds.), Saturn from Cassini-Huygens. Springer, NY, pp. 763–782. [5] Greeley and Batson, 1990, Planetary Mapping, Cambridge University Press, Cambridge. |
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