As the Near Earth Asteroid Rendezvous (NEAR) spacecraft silently races toward asteroid 433 Eros, it is making interplanetary history. An April 1 sighting from an Earth-based telescope made NEAR the most distant man-made object ever detected by optical means.
The spacecraft was seen by Gordon Garradd of Loomberah, New South Wales, Australia, at 20,909,000 miles (33,650,000 kilometers) from Earth. Garradd was aided by NEAR's 100 square feet of solar panels that fortuitously reflected sunlight directly at Earth for a few minutes following the spacecraft's successful 12th trajectory correction maneuver. For images of the Milky Way star field with NEAR's position, see Web site: http://usrwww.mpx.com.au/~gjg/near2.htm.
The previous record for sighting of a man-made object was the detection of the Galileo spacecraft several days before its second Earth swingby on Dec. 8, 1992. Galileo was imaged at a distance of 8.06 million kilometers with the University of Arizona's 70-inch Spacewatch telescope.
NEAR, now traveling at approximately 30 thousand mph (relative to Earth), has completed more than 1 billion miles of its journey since its launch on Feb. 17, 1996, and is more than halfway to a Jan. 10, 1999, rendezvous with asteroid 433 Eros. NEAR will be the first spacecraft to orbit an asteroid and to study its composition and characteristics at close range (as close as 9 miles from the surface).
David Dunham of the APL Mission Design Team says, "Excitement is building among the NEAR operations and science teams now that NEAR has literally turned the corner with last January's Earth swingby and is now closing in on Eros." Rendezvous activities are well under way, he says. "It's the last leg of NEAR's interplanetary journey, and work is nearly complete on the complex plans for the Eros rendezvous and early orbital phase operations."
NEAR, the first spacecraft powered by solar cells to operate beyond the orbit of Mars, has already experienced a cosmic encounter. On June 27, 1997, NEAR flew by asteroid 253 Mathilde coming to within approximately 750 miles (1200 kilometers), the closest ever to an asteroid. A deep-space maneuver on July 3, 1997, took NEAR back toward Earth for a slinghot gravity assist that put the spacecraft on target for Eros.
The next significant event of the NEAR mission is the detection of Eros by the spacecraft, which is expected to take place on Aug. 13 of this year, the 100th anniversary of the asteroid's discovery.
NEAR was the first launch in NASA's Discovery Program of low-cost, small-scale planetary missions. The spacecraft was built by The Johns Hopkins University Applied Physics Laboratory, Laurel, Md., which is also managing the mission.
NEAR Web site: http://near.jhuapl.edu