Publications (2)1.33 Total impact

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    ABSTRACT: Summary form only given. The Plasma Experiment for Planetary Exploration (PEPE) made detailed observations of the plasma environment of Comet Borrelly during the Deep Space I (S+DS I) flyby on September 22, 2001. Five distinct plasma boundaries have been identified on both inbound and outbound trajectories including those associated with cometary ion pickup, the comet bow shock, and the collisional transition region. All five boundaries were remarkably asymmetric with respect to the comet nucleus-Sun axis, normally thought to be an axis of symmetry. We suggest that the coma itself is offset, possibly because of well-collimated large dayside dust jets observed by the DSI MICAS camera.
    No preview · Article · Jan 2002 · Earth Moon and Planets
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    ABSTRACT: NASA's Deep Space 1 (DS1) spacecraft successfully encountered comet 19P/Borrelly near perihelion and the Miniature Integrated Camera and Spectrometer (MICAS) imaging system onboard DS1 returned the first high-resolution images of a Jupiter-family comet nucleus and surrounding environment. The images span solar phase angles from 88° to 52°, providing stereoscopic coverage of the dust coma and nucleus. Numerous surface features are revealed on the 8-km long nucleus in the highest resolution images(47–58 m pixel). A smooth, broad basin containing brighter regions and mesa-likestructures is present in the central part of the nucleus that seems to be the source ofjet-like dust features seen in the coma. High ridges seen along the jagged terminator lead to rugged terrain on both ends of the nucleus containing dark patches and smaller series of parallel grooves. No evidence of impact craters with diameters larger thanabout 200-m are present, indicating a young and active surface. The nucleus is very dark with albedo variations from 0.007 to 0.035. Short-wavelength, infrared spectra from 1.3 to 2.6 μm revealed a hot, dry surface consistent with less than about10% actively sublimating. Two types of dust features are seen: broad fans and highlycollimated “jets” in the sunward hemisphere that can be traced to the surface. The source region of the main jet feature, which resolved into at least three smaller “jets” near the surface, is consistent with an area around the rotation pole that is constantly illuminated by the sun during the encounter. Within a few nuclear radii, entrained dustis rapidly accelerated and fragmented and geometrical effects caused from extended source regions are present, as evidenced in radial intensity profiles centered on the jet features that show an increase in source strength with increasing cometocentric distance. Asymmetries in the dust from dayside to nightside are pronounced and may show evidence of lateral flow transporting dust to structures observed in the nightside coma. A summary of the initial results of the Deep Space 1 Mission is provided, highlighting the new knowledge that has been gained thus far.
    No preview · Article · Sep 2000 · Earth Moon and Planets