Ceres Dawn
Dawn sent a signal to confirm it was healthy and had entered orbit about 61,000 kilometers above Ceres March 6. Image of Ceres taken by the Dawn spacecraft March 1. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

WASINGTON — NASA’s Dawn spacecraft arrived in orbit around the dwarf planet Ceres March 6, completing a journey of nearly seven and a half years and five billion kilometers.

In a statement, NASA’s Jet Propulsion Laboratory said Dawn entered orbit about 61,000 kilometers above Ceres at 7:39 am EST March 6, sending a signal to Earth about an hour later confirming it was in orbit and in good health.

“We feel exhilarated,” Dawn principal investigator Chris Russell said in the statement. “We have much to do over the next year and a half, but we are now on station with ample reserves, and a robust plan to obtain our science objectives.”

Dawn will gradually spiral down to its initial science orbit, 13,500 kilometers above Ceres, by April. Later in its mission Dawn will move gradually closer to the surface, eventually moving into an orbit of 375 kilometers.

The Dawn spacecraft, built by Orbital ATK, launched on a United Launch Alliance Delta 2 rocket in September 2007. After making a gravity assist flyby of Mars in February 2009, it entered orbit around the large main-belt asteroid Vesta in July 2011. It remained there for more than a year, using its ion thrusters to leave orbit in September 2012 to head to Ceres.

Ceres, the largest object in the main asteroid belt between the orbits of Mars and Jupiter, was the first asteroid discovered by astronomers, in 1801. The International Astronomical Union designated Ceres a “dwarf planet” in 2006, a new category of objects that also includes the former planet Pluto.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...