November 12, 2007

Arecibo’s Role May Expand

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Five scientists, including Prof. Don Campbell, astronomy, testified before Congress this past Thursday at a hearing to discuss NASA’s plan to find and characterize potentially hazardous asteroids and comets.
Campbell’s role in the proceedings was to address the utility of Cornell’s Arecibo Observatory, the largest radio telescope in the world, in making detailed observations of potentially hazardous objects and helping to mitigate the threat they may pose to Earth. Campbell is the former site director of Arecibo and the former head of the observatory’s Planetary Radar Group.
The purpose of the Congressional hearing was to discuss the issue of potentially hazardous Near Earth Objects, asteroids or comets whose trajectories bring them close enough to Earth to make experts worry about a collision. Congress issued an act in 2005 that directed NASA to “detect, track, catalogue and characterize the physical characteristics” of all the nearby objects that have a diameter of 140 meters or larger — about the size of a luxury liner. Congress asked NASA to find 90 percent of these objects by 2020 at the latest. This past March, NASA replied with a report saying that, unless they could build a new telescope by 2015, the goal was unrealistic.
“It was essentially a feasibility request,” said Campbell. “Finding and characterizing 90 percent of NEOs by the 2020 deadline cannot be done using current plans for ground-based telescopes.”
NASA expects several telescopes that would have the necessary survey capabilities to be completed in the next five years, but most of them are intended for purposes other than just searching for asteroids. One of these is the Large Synoptic Survey Telescope, expected in 2012, which will survey the entire sky every seven days. In these frequent wholesale sweeps of the sky, the LSST will inevitably discover thousands of asteroids, said Campbell. However, its primary purpose is to study dark energy — not to catalogue asteroids.
“If the LSST spent full time searching for asteroids, it could probably meet the objective, if it in fact is in operation by 2012,” said Campbell. “But since they don’t plan to spend all of their time looking for asteroids, it would take them a number of years longer than that to achieve the 90 percent goal.”
NASA’s report proposed that the only way they could meet Congress’s objectives using ground-based telescopes was if they had a telescope similar to the LSST that was dedicated exclusively to finding asteroids. Such a telescope combined with the LSST and other telescopes could finish the project by 2020, but a dedicated asteroid-hunting telescope alone would take until 2024.
In addition to finding the majority of potentially hazardous NEOs, Congress has also asked NASA to determine how likely it is that any of these objects will collide with the Earth, and to figure out how we would stop it. To do this, NASA needs to determine things like the object’s size, mass, orbit around the sun and composition to a very high accuracy. This sort of measurement is the forte of planetary radar, a method of observation where scientists bounce radio waves off of the objects they wish to study, and make detailed images of them by listening to the echoes.
Arecibo’s planetary radar system is the most sensitive in the world, making it an enormous asset to scientists trying to prevent an asteroid impact. The Puerto Rico-based observatory’s financial future, though, has been in flux since early November 2006, when a Senior Review committee appointed by the National Science Foundation recommended that the observatory’s operating funds be cut by more than 50 percent by 2011. If Cornell and the observatory could not raise funds from another source, the NSF recommended that it close.
According to Campbell, “the Senior Review did not make any reference to the planetary program, even though many planetary astronomers wrote letters to them — to which little or no attention was paid.”
Campbell said that, although the main focus of the meeting was NASA’s report to Congress, “the issue of Arecibo and the use of radar to predict orbits for Near Earth Asteroids and particularly for those that potentially pose a threat to Earth was highlighted” by several Congressmen as well as scientists, including Rep. Dana Rohrabacher (R-CA). Rohrabacher and U.S. Rep. Luis Fortuño of Puerto Rico introduced a bill to the House of Legislation to secure future funding for Arecibo.
Rep. Fortuño also spoke at Thursday’s hearing, emphasizing the economic impact and loss of educational opportunities that Puerto Rico would suffer if Arecibo should close.
Campbell said no decision was reached by the end of the hearing.
“We’re certainly hoping that the Arecibo situation can be resolved,” he said. “There’s a great deal of activity going on. The summation of all that activity will come out to a happy outcome, but at the moment nothing has been settled upon.”