Asia-Pacific

US probe enters orbit around Mercury

(Xinhua)
Updated: 2011-03-18 13:05

WASHINGTON - NASA's MESSENGER spacecraft entered an orbit around Mercury late Thursday, capping an over-six-and-half-year journey to the solar system's innermost planet.

Illustration with pointers to key features of NASA's MESSENGER space probe which goes into orbit around the planet Mercury on Thursday. With mission timeline. [Photo/Agencies]

According to NASA, at 8:45 pm EDT (0045 GMT Friday), MESSENGER -- having pointed its largest thruster very close to the direction of travel -- fired that thruster for nearly 14 minutes, with other thrusters firing for an additional minute, slowing the spacecraft by 862 meters per second and consuming 31 percent of the propellant that the spacecraft carried at launch.

Less than 9.5 percent of the usable propellant at the start of the mission remained after completing the orbit insertion maneuver, but the spacecraft will still have plenty of propellant for future orbit correction maneuvers.

The orbit insertion placed the spacecraft into a 12-hour orbit about Mercury with a 200 km minimum altitude. At the time of orbit insertion, MESSENGER was 46.14 million km from the sun and 155.06 million km from Earth.

Launched on August 3, 2004, MESSENGER was the first spacecraft to orbit Mercury. The spacecraft followed a path through the inner solar system, including one flyby of Earth, two flybys of Venus, and three flybys of Mercury. This impressive journey is returning the first new spacecraft data from Mercury since the Mariner 10 mission over 30 years ago.

Beginning on April 4, MESSENGER will learn about Mercury's mysterious magnetic field and discover if the tiny, hot planet has ice in its permanently dark frigid craters near its poles.