High Precision Astrometry of Occulting Asteroids
- David Falk, Associate Professor of Astronomy, Los Angeles Valley College
- William Owen, Supervisor, Optical Navigation Group, Mission Design and Navigation Section, Jet Propulsion Labratory / California Institute of Technology
Author: Brandon L. Day
Mentor: Dr. William M. Owen Jr.
The work at JPL’s Table Mountain Observatory, on High Precision Astrometry of Occulting Asteroids is done using the 0.6m telescope with either a 4k CCD camera or a 2k CCD camera, depending upon which is able to provide the best results at the time. Both of these cameras have the ability, given favorable weather conditions, to provide excellent pictures and data of the targeted asteroids. Due to the refractive nature of the Earth’s atmosphere, we track and document the local temperature, barometer reading or atmospheric pressure, and humidity for each target. This data enables us to model the refractions into each picture, aiding in the overall precision. Each picture is also taken as close as possible to the meridian; which is when the object’s right ascension (RA) coincides with the local sidereal time. This should ensure that the picture of the target will be taken through the least amount of atmosphere, increasing accuracy. The process of data reduction after each night of observations provides the opportunity to eliminate errors in position that could occur. Such errors can be common given the distance and visible magnitude of the targets. After our data is reduced with all errors taken out, the data is then submitted to outside groups, the Minor Planet Center and Harvard's Astronomical Research Department, to be used in precisely calculating each target's orbit and position. The recalculated data will then be used to refine ground tracks of asteroid occultations. This new data is used to document where, from the Earth’s surface, each asteroid that passes in front of a star can best be viewed. The results of this research are not defined by numbers, or statements, however each additional observation adds more and more precision to current trajectory mapping.