AAS 201st Meeting, January, 2003
Session 61. Pluto-Occultation Studies
Oral, Tuesday, January 7, 2003, 10:00-11:30am, 616-617

[Previous] | [Session 61] | [Next]

[61.07] The Position of Pluto Relative to its Ephemeris

K.B. Clancy, J.L. Elliot, M.J. Person (MIT), A.S. Bosh (Boston Univ. & Lowell), M.W. Buie, E.W. Dunham, L.H. Wasserman (Lowell), S.E. Levine, R.C. Stone (USNO)

In order to predict the occultations of the stars P126 and P131.1 by Pluto on 2002 July 20 (UT) and August 21 (UT), respectively (see J.L. Elliot et al., 2002, BAAS 34, 877; Buie et al., 2002, BAAS 34, 877; Sicardy, et al., 2002, BAAS 34, 877), astrometric data sets were acquired on several telescopes. The data analyzed for the occultation predictions spanned more than three months (2002 May - 2002 August) and included 189 strip scans from the Lowell Astrograph, 22 frames from the USNO 1.55m, and 61 frames from the Lowell 0.6m at CTIO. The final prediction for closest approach distance appears to be within 100 km (about 0.005”) of the observed closest approach for the P126 occultation, and within 200 km (about 0.01”) for the P131.1 occultation (note that the angular half light radius of Pluto is about 0.06”; see Clancy et al., 2002, BAAS 34, 873; final predictions are at http://occult.mit.edu/research/occultations/Candidates/Predictions/P126.html and http://occult.mit.edu/research/occultations/Candidates/Predictions/P131.1.html). Pluto’s position in these frames was determined relative to a UCAC astrometric reference network (Zacharias et al., 2000, AJ 120, 2131), with a dual-source model fit to the blended Pluto-Charon image. The Pluto-Charon offset was fixed with JPL Horizon’s Ephemeris (PLU006 and DE-0406, LE-0406), and the Pluto-Charon light ratio was fixed at recent values (updated from Buie et al., 1997, Icarus 125, 233). The residuals of Pluto’s measured position from its ephemeris were then fit with a sinusoid of fixed period (Charon’s orbital period), while phase, offset, and amplitude were left as free parameters. The fitted phase and amplitude are mutually consistent for all data sets, and the relative amplitude of the RA and Dec sinusoids agree with the relative amplitude of Charon’s orbital motion. This implies either an incorrect Charon to Pluto mass ratio (0.12 was used to calculate the ephemeris), or that we used incorrect Pluto-Charon light ratios in this reduction. This work was funded in part by NASA grant NAG5-10444 and NSF grant AST-007 3447.

If you would like more information about this abstract, please follow the link to http://occult.mit.edu/research/occultations/Candidates/Predictions/P126.html. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

The author(s) of this abstract have provided an email address for comments about the abstract: kclancy@mit.edu

[Previous] | [Session 61] | [Next]

Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.