Proximity Enables Surface, Gravity Studies

NASA reports its Dawn spacecraft, launched in 2007 to study the giant asteroid Vesta, successfully maneuvered into its closest orbit around the big rock on Monday. The probe is now at an altitude averaging about 130 miles, beginning the phase of the mission known as low altitude mapping orbit.

"Dawn has performed some complicated and beautiful choreography in order to reach this lowest orbit," said Marc Rayman, Dawn chief engineer and mission manager based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We are in an excellent position to learn much more about the secrets of Vesta's surface and interior."

The primary goal of the low orbit is to collect data for the gamma ray and neutron detector (GRaND) and a gravity experiment. GRaND will be looking for the by-products of cosmic rays reflected off Vesta to reveal the identities of many kinds of atoms in the surface of Vesta. The instrument is most effective at this low altitude. Close proximity to Vesta also enables ultrasensitive measurements of its gravitational field. These measurements will tell scientists about the way masses are arranged in the giant asteroid's interior.

Orbital Sciences Corp. in Dulles, VA designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are international partners.

FMI: www.nasa.gov/dawn