NASA’s Dawn probe is right on target for its year-long orbital encounter with the huge asteroid Vesta, which is set to begin in July.

NASA said June 23 that Dawn is 155,000 kilometers from Vesta — the second-largest object in the main asteroid belt between Mars and Jupiter — and should enter into orbit around the 530-kilometer wide space rock in mid-July.

Dawn will then spend a year studying Vesta from above, marking the first time any spacecraft has made an extended visit to a large asteroid. Dawn will begin making science observations in early August.

Dawn has been chasing Vesta for nearly four years. Since its launch in September 2007, the spacecraft has logged about 2.7 billion kilometers, researchers said. Dawn is now halfway through its final approach to Vesta and has been snapping photos of the space rock with its navigation camera. “Our destination is within sight, and this team is very excited that we’re finally closing in on Vesta,” said Robert Mase, Dawn project manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

The huge space rock’s gravity will capture Dawn into orbit on July 16, when about 16,000 kilometers separate the pair. At that point, the probe and the asteroid will both be about 188 million kilometers from Earth.

Unlike many other spacecraft that go into orbit around other worlds, this capture will not require any dramatic maneuvers or last-minute burns, researchers said. Dawn has been using its low-thrust ion propulsion system to close in on Vesta’s orbit slowly but surely, so it should slip nicely into orbit on July 16.



Despite Delay, Dawn Still on Track to Rendezvous with Asteroids