Wheres the best place to park a space telescope to find a planet-killing asteroid; that is, a kilometer-scale object capable of threatening human civilization? A team of astronomers at NASAs Jet Propulsion Laboratory (JPL) has just concluded that the sweet spot for its proposed $500 million NEOCam (Near-Earth Object Camera) spacecraft is still relatively close to home.
Theyre talking the Earth-Sun L1 Lagrange point; a stable point of gravitational equilibrium, where soon after launch in 2021, NEOCam would set about discovering millions of new asteroids and comets. One goal is to determine their orbits with enough accuracy to figure out what miniscule fraction might also have the potential to catastrophically impact Earth.
In a paper to appear in The Astronomical Journal, the team describes computer simulations of a large swath of some 12,000 known near-Earth objects. The idea was to calculate how effective NEOCam would actually be at detecting objects as small as 140 meters when staring at an often observationally-confusing background of stars, galaxies, planets, minor planets, and known asteroids and comets.
Amy Mainzer, NEOCams Principal Investigator and an astronomer at NASA JPL, told Forbes. The first question is where do you put it? Weve now done detailed computer simulations that prove that staying relatively close to Earth is the best bet.
The Milky Way over an empty beach at Cape May, New Jersey. Credit: Chris Bakley (chrisbakleyphotography.com)
By staying at the Earth-Sun L1 point, Mainzer explains that the spacecrafts 50-cm telescope, equipped with Mercury Cadmium Telluride detectors, would be far enough from Earth to cool to temperatures near 40 Kelvin (or roughly minus 400 degrees F). This would enable the telescope to spot such distant dark asteroids while still close enough to receive mini-movies of such objects to the tune of 150 megabytes per second.
Between the inner solar system and Saturn lie millions of heretofore undetected asteroids and more than a few long-period comets; many of which are near-Earth objects (NEOs) that lurk on Earth-crossing orbits.
NEOCam is a candidate for selection as a NASA Discovery class mission later this Fall. If selected, its proposed 2021 launch would already fall a year after the U.S. space agencys initial Congressional deadline to find and characterize at least 90 percent of all NEOs larger than 140 meters.
Of some 12,000 known near-Earth objects (including both comets and asteroids), some 900 are thought to be planet-killing asteroids of a kilometer or more in diameter. Although roughly 90 percent of these kilometer-sized asteroids have been identified in known NEO populations, some 90 to 100 still remain undetected. The good news is that none of this known population are thought to be on Earth-impacting orbits. However, at least 90 to a 100 of these civilization-ending type objects still remain totally undetected. But Mainzer is quick to point out that NEOCam would have a good chance of finding the few remaining large ones out there.
With the NEOCam teams development of next generation mid-infrared detectors, during its five year nominal mission, the spacecrafts 32 megapixel camera, would be able to detect more than two-thirds of NEOs larger than 140 meters; thus making what the authors term a significant contribution in fulfilling the Congressional mandate.
See the article here:
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