After its nearly four-year trek, Nasa engineers are expected to confirm that the US spacecraft Dawn has entered the orbit of Vesta, one of the largest asteroids in the solar system.

Mission leaders estimate that Dawn was pulled into Vesta’s orbit around 5a.m. GMT on Saturday.

Dawn should come within 10,000 miles (16,000 kilometers) of Vesta to study its surface while travelling 188 million kilometres from earth.

“It has taken nearly four years to get to this point,” said Robert Mase, manager of the $466 million project at Nasa’s Jet Propulsion Laboratory in Pasadena, California.

“Our latest tests and check-outs show that Dawn is right on target and performing normally,” he added.

“We feel a little like Columbus approaching the shores of the New World,” said Christopher Russell, Dawn’s principal investigator, based at the University of California in Los Angeles. “The Dawn team can’t wait to start mapping this Terra Incognita.”

After a year of observations and measurements around Vesta, Dawn will depart for its second destination, the dwarf planet Ceres, in July 2012. It will be the first craft to orbit two solar system destinations beyond earth, said Nasa officials.