NASA's Dawn spacecraft obtained this image with its framing camera on 9 July 2011. It was taken from a distance of about 41,000 km away from the protoplanet Vesta. Each pixel in the image corresponds to roughly 3.8 km.
Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
PASADENA: NASA's Dawn spacecraft has become the first probe ever to enter orbit around an object in the main asteroid belt between Mars and Jupiter.
Dawn will study the asteroid, named Vesta, for a year before departing for a second destination, a dwarf planet named Ceres, in July 2012. Observations will provide unprecedented data to help scientists understand the earliest chapter of our Solar System. The data also will help pave the way for future human space missions.
"Today, we celebrate an incredible exploration milestone as a spacecraft enters orbit around an object in the main asteroid belt for the first time," NASA administrator Charles Bolden said of the US$466 million project.
"Dawn's study of the asteroid Vesta marks a major scientific accomplishment and also points the way to the future destinations where people will travel in the coming years. President Obama has directed NASA to send astronauts to an asteroid by 2025, and Dawn is gathering crucial data that will inform that mission."
Determining gravitational pull
The spacecraft relayed information to confirm it entered Vesta's orbit, but the precise time this milestone occurred is unknown at this time. The time of Dawn's capture depended on Vesta's mass and gravity, which only has been estimated until now.
The asteroid's mass determines the strength of its gravitational pull. If Vesta is more massive, its gravity is stronger, meaning it pulled Dawn into orbit sooner. If the asteroid is less massive, its gravity is weaker and it would have taken the spacecraft longer to achieve orbit.
With Dawn now in orbit, the science team can take more accurate measurements of Vesta's gravity and gather more accurate timeline information.
Record-breaker
Dawn is expected to come within 16,000 km of Vesta within four years while traveling 188 million km from Earth.
It will measure surface composition, topography and texture, plus the tug of gravity from Vesta and Ceres to learn more about their internal structures.
It also has a gamma ray and neutron detector instrument to gather information on cosmic rays as it approaches the asteroid belt, as well as an infrared mapping spectrometer.
