THE LOWELL OBSERVATORY NEAR-EARTH-OBJECT SEARCH:
A PROGRESS REPORT

Presented at The 27th Annual Meeting of the AAS/Division of Planetary Sciences (1995 October 9-13, Kohala Coast, Hawaii).

• Edward Bowell, Lowell Observatory, Flagstaff, Arizona, U.S.A.
• Bruce W. Koehn, Lowell Observatory, Flagstaff, Arizona, U.S.A.
• Steve B. Howell. Planetary Science Institute, Tucson, Arizona, U.S.A.
• Mark Hoffman, Yale University, New Haven, Connecticut, U.S.A.
• Karri Muinonen, Observatory, University of Helsinki, Finland

The Lowell Observatory Near-Earth-Object Search (LONEOS) is a system to survey asteroids and comets that has been under development for a little more than 2 years. Hardware consists of a 58-cm, f/1.91 Schmidt telescope, a CCD camera containing two Loral 2048 X 2048 chips (eventually, two 2048 X 4096 chips), a Silicon Graphics IRIS 4D/220GTX computer containing six processors, and other computers. The instantaneous field of view will be 10.1 deg².

To image the sky, the telescope will scan in declination at a rate up to 6 deg/min, corresponding to a data-acquisition rate of 1 Mb/s. The system will have the capability of scanning the entire accessible dark sky three times per lunation to a limiting magnitude that should exceed V_lim = 19.5. Scans will be made on fixed regions of the sky, so images of fixed celestial sources (stars, galaxies, etc.) and repeating cosmetic defects (diffraction spikes, bleeding form saturated stars, etc.) will always occupy known pixels. By co-adding a number of scans, we will build fixed-source maps, which will allow moving-target detection only in pixels thought to contain dark sky. Initially, such detections will be made only on the basis of data numbers exceeding a chosen threshold.

During the past few months we have been developing algorithms to maximize V_lim (i.e., minimize the S/N ratio and the false-positive detection rate). Because LONEOS is close to undersampling (untrailed images will occupy no more than 16 pixels), the detection process must be carried out with care. First, by examining unsaturated star images (~10⁵/scan), we determine the point-spread function (PSF, itself a function of zenith angle and off-axis distance in R.A.) to subpixel resolution. Then, by allowing the peak of the PSF to occupy each subpixel of the pixel containing the peak signal, we develop a family of "PSF masks." Finally, putative moving-target detections are tested against the masks, and are accepted or rejected on the basis of chi-squared tests. The best-fit mask provides position and brightness estimates

Research supported, in part, by NASA grant NAGW-3397.

Last updated 1 Mar 1996

Contact: Bruce Koehn (koehn@lowell.edu)
Web Curators: Ted Bowell and Bruce Koehn

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