Dawn Spacecraft to Enter Vesta's Orbit Tomorrow

NASA’s Dawn spacecraft is closing in on its quarry, the asteroid Vesta.

Vesta is one of the largest asteroids in the belt of rocky debris between Mars and Jupiter. Dawn was launched four years ago and has been studying the asteroid during its approach to allow engineers to fine tune the spacecraft’s trajectory. As NASA said today, Dawn will “ease up” on Vesta and allow the asteroid’s minuscule gravity field to capture the spacecraft into orbit.

That moment is expected late tomorrow night Pacific time, or early Saturday morning on the East Coast. The exact time is 10:00 pm PDT (1:00 am Saturday, EDT) although it will not be until an hour and a half later that NASA will be able to confirm capture during a scheduled communications opportunity. The spacecraft/asteroid duo will be 117 million miles from Earth at that time. By comparison, the Moon is 240,000 miles from Earth on average.

Dawn will stick with Vesta for a year and then move on to Ceres, which once was designated as an asteroid itself, but now is classified as a dwarf planet along with Pluto and Eris. Scientists want to learn more about asteroids because they provide clues about the earliest days of solar system formation and to know as much as possible about any that head on a collision course with Earth.

President Obama wants NASA to send astronauts to an asteroid by 2025 and NASA Administrator Charlie Bolden linked the Dawn mission with that goal at a congressional hearing on Tuesday, although Dawn was planned long before the President’s April 2010 announcement. NASA has selected another asteroid mission, OSIRIS-ReX, for launch in 2016. That mission will return a sample from an asteroid designated 1999 RQ36.

The Jet Propulsion Laboratory manages the Dawn mission for NASA, while the University of California, Los Angeles (UCLA) is in charge of the mission science. Germany and Italy are part of the mission team, and Orbital Sciences Corp. built the spacecraft.