After a nearly four-year journey, the Dawn spacecraft is scheduled to get up close and personal with the asteroid Vesta early Saturday morning, the first mission that has entered the orbit around a main-belt asteroid.
Engineers believe the spacecraft will be captured by Vesta's orbit at approximately 1am Eastern on July 16, though they won't know if it worked until a scheduled communications pass at 2:30am. The team will also need a few days to determine the exact time Dawn made it into orbit. When it does make that transition, Dawn will be about 9,000 miles away from the asteroid and 117 million miles away from Earth.
"It has taken nearly four years to get to this point," Robert Mase, Dawn project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a statement. "Our latest tests and check-outs show that Dawn is right on target and performing normally."
According to NASA, Dawn does not utilize the same propulsive burn techniques like those used for orbit insertion around a planet (like Mercury); instead, Dawn will "ease up" next to Vesta, after which the asteroid's gravitational pull will capture the spacecraft.
Dawn has been snapping photos during its approach, the most recent of which was taken about 26,000 miles from Vesta. Images taken by Dawn are twice as sharp as those captured by NASA's Hubble Space Telescope, but surface details about the asteroid are still unknown, something this mission will help clear up. The first "close" shots of Vesta will be captured about 1,700 miles away from the asteroid before moving about 420 miles above it, and then, 120 miles.
Dawn will study Vesta for one year, gathering observations that NASA said will help scientists understand the earliest chapter of our solar system's history. Dawn will then depart for its second destination, the dwarf planet Ceres, in July 2012.