MESSENGER Completes Its 1,000th Orbit of Mercury

MESSENGER will complete its 1,000th orbit of the planet closest to the Sun at 11:22 p.m. EDT tonight (22 June 2012). “Reaching this milestone is yet another testimony to the hard work and dedication of the full MESSENGER team that has designed, launched, and operated this highly successful spacecraft,” says the mission trajectory lead Jim McAdams of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

The spacecraft was inserted into orbit around Mercury in mid-March 2011, after travelling more than 15 times around the Sun through the inner solar system and completing six planetary flybys. “Since arriving at Mercury, MESSENGER took a little more than 15 months to reach this mark,” McAdams notes. “But because the orbital period has been reduced from just under 12 hours to 8 hours, it will take only 11 months to complete the next 1,000 orbits.”

During its primary mission, which concluded on March 17, 2012, MESSENGER performed the first global reconnaissance of the geochemistry, geophysics, geologic history, atmosphere, magnetosphere, and plasma environment of Mercury. The spacecraft is now more than one-quarter of the way into a one-year extended mission that is building on this knowledge to address new questions raised by the initial orbital observations.

“Mercury is in a tough neighborhood, with high temperatures and increasingly frequent streams of solar energetic particles,” says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. “It is therefore all the more remarkable that this spacecraft has met the challenge to perform as designed after 1,000 orbits about the innermost planet in our solar system. There is much more science ahead for this mission.”