Cassini RPWS observations of dust in Saturn's E Ring |
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| Institution: | 1. Max-Planck-Institut für Kernphysik, Heidelberg, Germany, and HIGP, University of Hawaii, Honolulu, USA;2. University of California, Berkeley, USA;3. SETI Institute, Mountain View, USA;4. University of California, Berkeley, USA;5. Max-Planck-Institut für Kernphysik, Heidelberg, Germany;1. Graduate School of System Informatics, Kobe University, Kobe, Japan;2. Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Japan;1. Astronomy Department, University of California, 601 Campbell Hall, Berkeley, CA 94720-3411, United States;2. Faculty of Aerospace Engineering, Delft University of Technology, 2629 HS Delft, The Netherlands;3. SRON Netherlands Institute for Space Research, 3584 CA Utrecht, The Netherlands;4. Astronomy Department, Sierra College, Rocklin, CA 95677, United States;5. Astronomical Institute ‘Anton Pannekoek’, Science Park 904, 1098 XH Amsterdam, The Netherlands;6. SETI Institute, 189 Bernardo Avenue, Mountain View, CA 94043, United States;7. Association of Universities for Research in Astronomy, 1212 New York Avenue NW, Suite 450, Washington, DC 20005, United States;8. Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, United States;9. Caltech Optical Observatories, California Institute of Technology, MC 301-17, Pasadena, CA 91125, United States;10. Flat Wavefronts, Christchurch, New Zealand;11. Gemini South, AURA, Casilla 603, La Serena, Chile;12. Lawrence Livermore National Laboratory, Livermore, CA 94550, United States;1. Department of Physics and Astronomy, University of Leicester, University Road, Leicester, UK;2. LPAP, Institut d?Astrophysique et de Géophysique, Université de Liège, Liège, Belgium;3. Center for Space Physics, Boston University, 957 Commonwealth Ave., Boston, MA 02215, USA;4. Centre Spatial de Liège, Université de Liège, Liège, Belgium |
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| Abstract: | The Cassini radio and plasma wave science (RPWS) instrument is sensitive to few-micron dust grains impacting on the spacecraft at relative speeds of order 10 km/s. Through the first year or so of operations in orbit at Saturn, the RPWS has made a number of both inclined and equatorial crossings of the E ring, particularly near the orbit of Enceladus. Assuming water ice grains, the typical size particle detected by the RPWS has a radius of a few microns. Peak impact rates of about 50 s?1 are found near the orbit of Enceladus corresponding to densities of order 5×10?4 m?3. The variation of dust fluxes as a function of height above or below the equator is well described by a Gaussian distribution with a scale height of about 2800 km although there is usually some non-Gaussian variation near the peak fluxes suggesting some structure in the core of the ring. Offsets of the peak number densities are typically of the order of a few hundred km from the geometric equator. A near-equatorial radial profile through the orbit of Enceladus shows a sharply peaked distribution at the orbit of the moon. A size distribution averaged over several passes through the orbit of Enceladus is determined which varies as m?2.80. The peak in dust number density at the orbit of Enceladus is consistent with previous optical measurements and strongly supports the suggestion that Enceladus is a primary source for E ring particles. |
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