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D. J. Tholen, M. S. Connelley (University of Hawaii)
As of the abstract deadline, 481 Kuiper belt objects have been discovered, but only 50 have four-opposition or greater orbits. Historically, some of the three-opposition orbits still had assumed eccentricities, indicating the relative level of inaccuracy in the orbit determination. Meanwhile, several authors have published eccentricity versus semimajor axis plots for Kuiper belt objects without attaching error bars to the symbols. Caution should therefore be exercised when looking at the relative populations of resonant, classical, and scattered objects, or when reaching conclusions about mechanisms at work that shape the Kuiper belt. We have been working to ameliorate this situation by securing follow-up astrometric observations of Kuiper belt objects with shorter arc orbit solutions, thereby extending the arcs and improving the accuracy of their semimajor axis and eccentricity determinations. Approximately 30 objects have been recovered to date, including a serendipitous observation of the satellite of 1998 WW31. We will be presenting improved estimates of the relative populations of resonant, classical, and scattered objects at the DPS meeting.
Emphasis has also been given to astrometric observations of faint near-Earth objects to prevent their ephemeris uncertainties from growing large enough to warrant being tagged as "lost". In some cases, arcs have been extended by a factor of more than sixty. Virtually all of our observations are the last available for these objects. The number one reason for failure to recover an object has been low galactic latitude, where the field star density is so high that after non-sidereal tracking is taken into account, the field of view is nearly completely covered by star trails. Notable recoveries include 2000 SG344 at magnitude 26 in 2001 August using the CFHT (this object had been identified as having a 1 in 1000 chance of colliding with the Earth in 2071), 2000 GD147 at magnitude 24.5 in 2001 September using the UH 2.24-m, 2000 UR13 (we repaired an erroneous orbit that resulted from a bad identification), and 2000 VN2 (an object that had been prematurely numbered, based on erroneous single-night precovery observations).
This work has been supported by NASA Grant No. NAG5-4524.