Spacewatch Observations of Near-Earth Objects
Abstract
Spacewatch specializes in followup of NEOs of high priority while they are faint, producing an annual average of ~8500 lines of astrometry of ~1,000 different NEOs. We contribute to the removal of half of the objects that were retired from impact risk lists. Our observations at elongations as small as 46 deg support followup of hazardous NEOs and NEOs discovered by the NEOWISE spacecraft. Per year we observe about 35 radar targets, 50 NEOs that were measured by NEOWISE, and 100 potential rendezvous destinations. In the last 3 years we have observed 50% of all NEOs observed in that time and 54% of all PHAs observed in that time. We lead in followup of provisionally designated PHAs while faint (V>= 22); contributing 41% of all such observations. With the Steward Obs. 0.9-m telescope, site code 691, we survey with a mosaic of CCDs near opposition and at low elongation in the east. Coverage is 1400 sq. deg per lunation; V mag limit ~20.5-21.7. The 12 yrs of uniform surveying will go live on the web in 2015 to support incidental astrometry & precoveries of NEOs. On the Spacewatch 1.8-m telescope, site code 291, the FOV = 20x20 arcmin and the pixel scale = 0.6 arcsec/pixel. V mag limit=23 and the astrometric residuals are +/-0.3 arcsec. Our output with the Bok 2.3-m & Mayall 4-m telescopes from 2010-2014 was 1316 lines of astrometry on 207 different NEOs, including 84 different PHAs. 343 observations were made of PHAs with V>=22. Our average calendar span extension on large PHAs is 6 mo, 2x longer than the next most effective observing station. We extend the span of calendar time coverage on PHAs an average of 3.8x. For 38 of 72 PHAs we added another observed opposition. With the Bok & Mayall we reduce uncertainties of orbital elements an average of a factor of 6 and the uncertainty of the time of perihelion passage an average of a factor of 19 (G. Williams 2014 private communication). We gratefully acknowledge NASA's NEO Observation Program, The IAU's Minor Planet Center, JPL's NEOWISE Team led by A. K. Mainzer, JPL's NEO Office, Kitt Peak National & Steward Observatories, the U. S. Naval Academy, the estates of R. L. Waland and R. S. Vail, and other private donors.
- Publication:
-
IAU General Assembly
- Pub Date:
- August 2015
- Bibcode:
- 2015IAUGA..2221001M