Sentry (monitoring system)
Sentry is a highly automated collision monitoring system that continually scans the most current asteroid catalog for possibilities of future impact with Earth over the next 100 years. Whenever a potential impact is detected it will be analyzed and the results immediately published on the Near Earth Object Program.
Two or three weeks of optical data is not enough to conclusively identify an impact years in the future. By contrast, eliminating an entry on the risk page is a negative prediction; a prediction of where it will not be. As far as the public is concerned, it just isn't worth getting worried about an object with a couple weeks of optical data showing a possible Earth encounter years from now.
The Impact Risk page lists a number of lost objects such as 2004 BX159 that are, for all practical purposes, permanent residents of the risk page; their removal may depend upon a serendipitous rediscovery. Some objects on the Sentry Risk Table, such as 2000 SG344, might even be man-made.
The diameter of most near-Earth asteroids that have not been studied by radar or infrared can generally only be estimated within about a factor of 2 based on the asteroids absolute magnitude (H). More than two dozen known asteroids have better than a one in a million chance of impacting into Earth within the next 100 years.
- "Sentry Risk Table". NASA/JPL Near-Earth Object Program Office. 14 Oct 2011. Retrieved 2011-10-14.
- Jon Giorgini (30 July 2002). "Understanding Risk Pages". Columbine, Inc. (hohmanntransfer). Retrieved 2011-11-21.
- "IMPACT RISK ASSESSMENT: AN INTRODUCTION". NASA/JPL Near-Earth Object Program Office. 31 Aug 2005. Retrieved 2011-10-14.
- Donald K. Yeomans (9 February 2013). "Beware of Errant Asteroids". New York Times. Retrieved 10 February 2013.
- SENTRY - An Automatic Near-Earth Asteroid Collision Monitoring System@ neo.jpl.nasa.gov
- IMPACT RISK ASSESSMENT: AN INTRODUCTION
- Sentry Risk Table
- NEODyS CLOMON2
- List of objects for which all previously detected potential impacts have been eliminated
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