shows the 1.8-meter Steward Observatory
Since even before Comet Shoemaker-Levy's fiery encounter with Jupiter spurred the creation of numerous sky surveys to locate objects that could collide with Earth, the Spacewatch
survey has been finding near-Earth asteroids; it made its first discovery in 1991. In late 2003, Spacewatch started enlisting public
volunteers to help search its images (up to ~800 generated every clear night and posted online) for these fascinating objects. This is a mutually beneficial
relationship; it helps the Spacewatch team to quickly review the voluminous number of images to enable the prompt reporting of any asteroids, maximizing the chances of their confirmation
by other observatories, and it allows amateur astronomers and the general public to participate in an exciting project and help to discover these small (yet potentially deadly) worlds.
The Spacewatch project uses the Steward Observatory's 0.9- and 1.8-meter telescopes at Kitt Peak National Observatory in Arizona. (Images reviewed by the FMO Project are taken with the 0.9m scope.) It operates on clear nights except for around 10 days each month when the Moon is bright enough to wash out any faint asteroids; at least one observer controls the telescope and takes the images. The images are uploaded for review in batches of up to 112 to the FMO Project site, where reviewers can access them one at a time; even a large batch can be gone within minutes as reviewers quickly work through them. On an average night, about 50 volunteer reviewers participate.
An "FMO" (which stands for fast-moving object, generally an asteroid passing fairly close to Earth) appears as a short streak of light due to the asteroid's motion over the two minutes of the exposure. Reviewers click on FMO candidates to submit them to Spacewatch, which automatically returns a triplet of images of the same region of the sky taken 40 minutes apart, and a reviewer can resubmit objects that still look suspicious in the triplet. Various objects and artifacts, including but not limited to edge-on galaxies, several stars in a close line, stellar diffraction spikes, edge-on galaxies, "ghosting", CCD defects, cosmic ray hits, satellites, and meteors, can be mistaken for FMOs, and the vast majority of objects submitted or resubmitted for review prove to be false alarms. Still, since September 2003, when the project went public, FMO Project volunteers averaged nearly two confirmed asteroid discoveries per month (43 by March 2006--a remarkable 11 discoveries in October 2005 alone--plus 15 more that were too faint and/or fast-moving to be confirmed). It is not easy to find one of these asteroids; a new one is discovered every 2,000 images or so. Many are quite obvious and take little skill to detect, while finding shorter and/or fainter ones is more of a challenge. Still, it's the luck of the draw who gets the image with an asteroid on it, the important thing is for the reviewer to know what to look for.
Update: The Spacewatch FMO Project closed its doors on March 8, 2006, with only a day's warning to its participants. The official reason was that the grant from the Paul G. Allen Foundation had run out. It is unknown whether Spacewatch had attempted to renew the grant or find alternate funding. One project volunteer suggested that the Spacewatch staff let it lapse, as they were frustrated at a high rate of false resubmissions, but the full reasons remain unknown. At any rate, Spacewatch will continue its near-Earth object search without us volunteers. It was fun while it lasted, though I'll be happy to reacquaint myself with a thing called sleep.