The Spaceguard program, originally mandated by Congress in the 1990s, is in the business of detecting, tracking and cataloging near-Earth objects (NEOs). Spaceguard’s goal has always been as ambitious as it is crucial: To locate ninety percent or more of the objects that approach the Earth and are more than one kilometer in diameter. So how is Spaceguard doing? According to Stephen M. Larson (University of Arizona), who manages the Catalina Sky Survey, “We’re about 85 percent there.”
But even when we reach 100 percent, the story is far from over. An object just a third of a kilometer in diameter would explode with an energy more than twenty times that of the largest thermonuclear bomb. NASA received another mandate in 2005 to identify near-Earth asteroids and comets down to 140 meters in diameter, still large enough to destroy a city. And even though impacts like these seem to occur only once every several thousand years, no one can say when the next potential strike could happen.
I’m looking at a University of Arizona news release that notes the Catalina Sky Survey’s score in 2008: 565 NEO discoveries, following 460 in 2007. A $3.16 million NASA grant has now been awarded to continue the search through 2012 using the CSS facilities, which include a new 1-meter telescope to be housed next to the existing 1.5-meter instrument on Mount Lemmon, north of Tucson. Used to follow up NEO discoveries, the telescope boosts CSS’ survey time on other instruments by 20 to 25 percent.
But CSS also includes a southern hemisphere presence in New South Wales using Australian National University’s 0.5-meter telescope, a reminder of the need for global search facilities. It was CSS that identified 2008 TC3, a six-foot object that disintegrated over Sudan last fall. Says Larson:
“There’s a bit of a misperception that what we do is find objects that are incoming, like the Sudan object. That’s not the case.
“We’re hoping to find objects that many orbits down the road might be hazardous, so that we have enough time to do something about them. We can calculate orbits quite accurately. We hope that we would have a few decades to study and characterize these things, and come up with the best plans to nudge them into another orbit so that it misses the Earth.”
The numbers here are stark. NASA’s Near Earth Object Program reports that we’ve found 5,955 NEOs, some 763 of which are at least one kilometer in diameter. 1008 NEOs larger than 140 meters across come within 4.5 million miles of Earth’s orbit, dangerous to us because perturbing influences could change their trajectories in the future. Centauri Dreams believes that the discovery of an object on a collision course with Earth would galvanize the space program as researchers looked for the best ways to deflect its path. The problem is time.
Would we find the object soon enough to be able to develop the needed technologies? Ponder this: 2008 TC3 was discovered when it was well outside the orbit of the Moon. Moving at 12 kilometers per second, it struck some nineteen hours later.
The more accurate our sky surveys, the more likely we are to find objects while we still have a chance to deflect them. The best insurance program for our planet involves not only observing programs to detect and characterize the potential trouble-makers, but a robust effort to study deflection strategies. Part of this must include a mission to a near-Earth asteroid, not only to learn more about the object itself, but to tune up the procedures for getting a payload on site quickly if the need arises.