Authors: Pascu Dan, Rohde James R., Seidelmann P. Kenneth, Wells Eddie N., Hershey John L., Storrs Alex D., Zellner Ben H., Bosh Amanda S., and Currie Douglas G.
Year: 2004
Title: Hubble Space Telescope Astrometric Observations and Orbital Mean Motion Corrections for the Inner Satellites of Neptune
Journal: Astronomical Journal
Volume: 127
Number: 5
Pages: 2988-2996
Keywords: Neptune, small, theory, analytical
Abstract: Six small inner satellites of Neptune were imaged in 1989 with Voyager 2. In 1997, we recovered the four outermost with the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 for astrometric, dynamical, and photometric studies. The ring arcs were not detected in our images. Thirteen exposures were taken in each of three HST orbits: two orbits on July 3 and one on July 6. Exposures were taken in the BVI filters. Measurable images of Neptune and Triton were also obtained on the same PC1 frames with those of the faint satellites. We present here the astrometric observations of these four satellites relative to Neptune, as well as corrected orbital mean motions for them. Field distortions in the PC1 chip were corrected with both the Trauger et al. and the Anderson & King distortion models. Calibration of the scale and orientation was accomplished by comparing the measured positions of Neptune and Triton with an accurate JPL J2000 ephemeris. Separate calibrations were made for both distortion models. Small differences were detected in the calibrations, dependent on wavelength, saturation, and filter, and a small difference was found between the calibrations resulting from both distortion correction models. The resulting separation and position angle observations for the inner satellites were compared with the orbits of Owen et al. and corrections derived to their mean daily motions. A small but significant discrepancy was found for Proteus between the correction derived from the observations of separation and that from the position angles. This was shown not to be due to calibrational errors but, apparently, to the need for improvement of other orbital elements-at least for Proteus. Despite this anomaly, the mean motion accuracies were improved by almost 2 orders of magnitude as a result of the longer baseline since the Voyager observations. More HST observations of these satellites are recommended in order to improve their orbits further and for the investigation of satellite-ring interactions.
%F: AA(US Naval Observatory, 3450 Massachusetts Avenue, NW, Washington, DC 20392-5420 <EMAIL>pascu.dan@usno.navy.mil</EMAIL>, <EMAIL>jrohde@ngs.noaa.gov</EMAIL>), AB(US Naval Observatory, 3450 Massachusetts Avenue, NW, Washington, DC 20392-5420 <EMAIL>pascu.dan@usno.navy.mil</EMAIL>, <EMAIL>jrohde@ngs.noaa.gov</EMAIL>), AC(Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903; <EMAIL>pks6n@virginia.edu</EMAIL>), AD(Computer Sciences Corporation, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218; <EMAIL>wells@stsci.edu</EMAIL>), AE(Computer Sciences Corporation, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218; <EMAIL>wells@stsci.edu</EMAIL>), AF(Department of Physics, Astronomy, and Geosciences, Towson University, 8000 York Road, Baltimore, MD 21252; <EMAIL>astorrs@towson.edu</EMAIL>), AG(Department of Physics, Georgia Southern University, Landrum Box 8031, Statesboro, GA 30460; <EMAIL>zellner@gasou.edu</EMAIL>), AH(Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215and Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001; <EMAIL>amanda@lowell.edu</EMAIL>), AI(Department of Physics, University of Maryland, College Park, MD 20742; <EMAIL>currie@hubble.physics.umd.edu</EMAIL>)
Bibliogaphic Code: 2004AJ....127.2988P
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