Dawn Enters Orbit Around Vesta

Mission controllers at the NASA Jet Propulsion Laboratory (JPL), in Pasadena, California, confirmed that the Dawn spacecraft successfully entered orbit around the giant asteroid Vesta, on Saturday, July 16. The maneuver took place 117 million miles away from Earth.

This achievement marks the first time that a spacecraft made its way into the orbit of an object that orbits the Sun inside the Inner Asteroid Belt. This formation lies between the orbits of Mars and Jupiter.

Vesta is the largest asteroid in our solar system, and many experts believe that the object can even be considered a protoplanet. Its large diameter and peculiar surface features make it an exquisite target for space exploration.

Dawn managed to catch up with the massive space rock after steadily chasing it for more than four years. The probe launched from Space Launch Complex 17B (SLC-17B) at the Cape Canaveral Air Force Station (CCAFS) on September 27, 2007, aboard a Delta II delivery system.

Since then, its ion thrusters have constantly been guiding it towards a rendezvous with Vesta this July. Dawn will remain at its current location for about a years, before finally leaving the asteroid behind.

At that time, it will begin the second leg of its journey, whose mission will be to study the dwarf planet Ceres. The object lies in the IAB as well, and the NASA probe is scheduled to achieve orbital insertion around it in February 2015.

“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 on Saturday.

“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,” the top official went onto say.

“President Obama has directed NASA to send astronauts to an asteroid by 2025, and Dawn is gathering crucial data that will inform that mission,” he added. NASA invested about $466 million in this probe.

Even though Dawn relayed information back to Mission Control as it entered orbit around Vesta, JPL scientists don't yet know the exact moment when the spacecraft was captured in Vesta's orbit. Subsequent analysis of the telemetry will undoubtedly clear this mystery.

“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,” a NASA press release explains.

“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,” the document adds.

“With Dawn now in orbit, the science team can take more accurate measurements of Vesta's gravity and gather more accurate timeline information,” it concludes.