NASA's Dawn spacecraft, which has began a new phase in its mission called "low-altitude mapping orbit," is in an excellent position to have a closer look yet at the asteroid Vesta as it zooms nearer to the giant space rock's surface.

Dawn is in the middle of a yearlong campaign to study Vesta and the dwarf planet Ceres to learn more about our solar system's history using these leftover pieces of its formation, NASA said.

Vesta is the second most massive object in the asteroid belt between Mars and Jupiter, and at 330 miles (530 kilometers) wide, the protoplanet that could have developed into a full-fledged planet like Earth or Mars had Jupiter not stripped too much material away in the early days of the solar system, astronomers said.

"Dawn has performed some complicated and beautiful choreography in order to reach this lowest orbit," Marc Rayman, Dawn chief engineer and mission manager based at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

With the Dawn at about 130 miles (210 km) above Vesta, "we are in an excellent position to learn much more about the secrets of Vesta's surface and interior," he said.

"Dawn's visit to Vesta has been eye-opening so far, showing us troughs and peaks that telescopes only hinted at," said Dawn's principal investigator Christopher Russell of UCLA. "It whets the appetite for a day when human explorers can see the wonders of asteroids for themselves."

In 2025, NASA plans to send astronauts to visit an asteroid. Space officials said that missions like Dawn provide a vital opportunity to preview the scene that people will one day encounter.

The Dawn spacecraft was launched in 2007 and has been orbiting Vesta since July 15. The $466 million spacecraft will stay in its low-altitude mapping orbit for at least 10 weeks after which the probe will spiral back to its high-altitude mapping orbit at about 420 miles (680 km) in altitude.

The spacecraft will depart Vesta in July 2012 and is expected to reach its second target, Ceres, the largest space rock in the solar system's asteroid belt, in February 2015.