The Palomar Planet-Crossing Asteroid Survey (PCAS) was an astronomical survey, initiated by American astronomers Eleanor Helin and Eugene Shoemaker at the U.S Palomar Observatory, California, in 1973.[2][3][4][5] The program is responsible for the discovery of 95 near-Earth Objects including 17 comets,[6] while the Minor Planet Center directly credits PCAS with the discovery of 20 numbered minor planets during 1993–1994.[1] PCAS ran for nearly 25 years until June 1995. It had an international extension, INAS, and was the immediate predecessor of the outstandingly successful NEAT program.[6]
The first NEO discovered by PACS was (5496) 1973 NA, an Apollo asteroid with an exceptional orbital inclination of 68°, the most highly inclined minor planet known until 1999. In 1976, Eleanor Helin discovered 2062 Aten,[7] the first of a new class of asteroids called the Aten asteroids with small orbits that are never far from Earth's orbit. As a result, these objects have a particularly high probability of colliding with the Earth. In 1979, Helin discovered an Apollo-type asteroid, that they later identified with the comet 4015 Wilson–Harrington.[8] It was the first confirmation that a comet can evolve into an asteroid after it has degassed.[6]
^Leverington, David (2003). Planetary vistas : a history of planetary astronomy up to the 21st century. New York: Cambridge University Press. pp. 339–340. ISBN9780521808408.
^Gehrels, Tom, ed. (1994). Hazards due to comets and asteroids. Tucson: Univ. of Arizona Press. pp. 129–131, 137. ISBN9780816515059.
^Barnes-Svarney, Patricia (2003). Asteroid : earth destroyer or new frontier? (Paperback ed.). Cambridge, Mass.: Basic Books, a member of the Perseus Books Group. p. 246. ISBN9780738208855.
^Levy, David H. (2002). Shoemaker by Levy: the man who made an impact. Princeton, N.J.: Princeton University Press. pp. 167–174. ISBN9780691113258.