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Occultation Predictions Using CCD Strip-Scanning AstrometryWe are developing the method of CCD strip-scanning astrometry for the purpose of deriving reliable advance predictions for occultations involving small objects in the outer solar system. We are using a camera system based on a Ford/Loral 2Kx2K CCD with the Crossley telescope at Lick Observatory for this work. The columns of die CCD are aligned East-West, the telescope drive is stopped, and the CCD is clocked at the same rate that the stars drift across it. In this way we obtain arbitrary length strip images 20 arcmin wide with 0.58" pixels. Since planets move mainly in RA, it is possible to obtain images of the planet and star to be occulted on the same strip well before the occultation occurs. The strip-to-strip precision (i.e. reproducibility) of positions is limited by atmospheric image motion to about 0.1" rms per strip. However, for objects that are nearby in R.A., the image motion is highly correlated and their relative positions are good to 0.02" rms per strip. We will show that the effects of atmospheric image motion on a given strip can be removed if a sufficient number of strips of a given area have been obtained. Thus, it is possible to reach an rms precision of 0.02" per strip, corresponding to about 0.3 of Pluto or Triton's angular radius. The ultimate accuracy of a prediction based on strip-scanning astrometry is currently limited by the accuracy of the positions of the stars in the astrometric network used and by systematic errors most likely due to the optical system. We will show the results of . the prediction of some recent occultations as examples of the current capabilities and limitations of this technique.
Document ID
20020006943
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Dunham, Edward W.
(NASA Ames Research Center Moffett Field, CA United States)
Ford, C. H.
(Search for Extraterrestrial Intelligence Inst. CA United States)
Stone, R. P. S.
(Lick Observatory CA United States)
McDonald, S. W.
(Massachusetts Inst. of Tech. MA United States)
Olkin, C. B.
(Massachusetts Inst. of Tech. MA United States)
Elliot, J. L.
(Massachusetts Inst. of Tech. MA United States)
Witteborn, Fred C.
Date Acquired
August 20, 2013
Publication Date
January 1, 1994
Subject Category
Astrophysics
Meeting Information
Meeting: Division for Planetary Sciences Meeting
Location: Washington, DC
Country: United States
Start Date: October 1, 1994
Sponsors: Lunar and Planetary Inst.
Funding Number(s)
PROJECT: RTOP 352-02-03
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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