Vesta is the asteroid that Asimov used in one of his very first published stories, "Marooned Off Vesta."
Yahoo News: US spacecraft to be pulled into giant asteroid's orbit
.After its nearly four-year trek, NASA engineers are expected to confirm this weekend 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 0500 GMT Saturday and engineers should be able to confirm this when the space craft performs a scheduled communication pass at 0630 GMT Sunday, according to the US space agency.
Dawn should come within 10,000 miles (16,000 kilometers) of Vesta to study its surface while traveling 116 million miles (188 million kilometers) 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 (UCLA). "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.
The foremost objective of Dawn's eight-year mission is to compare and contrast the two giant bodies, which NASA says will help scientists "unlock the secrets of our solar system's early history."
"Dawn's science instrument suite will measure surface composition, topography and texture. In addition, the Dawn spacecraft will measure the tug of gravity from Vesta and Ceres to learn more about their internal structures," NASA said in a press release.
The spacecraft, which was launched in 2007, has a gamma ray and neutron detector instrument, which will gather information on cosmic rays during the approach phase, as well as an infrared mapping spectrometer.
The mission, which can be followed on NASA's website at http://dawn.jpl.nasa.gov, comes as a far more famous space craft, the shuttle Atlantis, orbits the Earth on the final mission of the 30-year shuttle program.
Private enterprise is working feverishly to come up with a next-generation US space capsule for cargo and crew.
US President Barack Obama has said such a capsule is crucial for sending astronauts beyond low Earth orbit to an asteroid and to Mars.