MESSENGER Modifies Orbit to Prepare for Low-Altitude Campaign
June 17, 2014
MESSENGER successfully completed the first orbit-correction maneuver of its Second Extended Mission this morning to raise its minimum altitude above Mercury from 113.9 kilometers (70.8 miles) to 155.1 kilometers (96.4 miles). This maneuver is the first of four designed to modify the spacecraft's orbit around Mercury so as to delay the spacecraft's inevitable impact onto Mercury's surface and allow scientists to continue to gather novel information about the innermost planet.
During the primary phase of the MESSENGER mission, the spacecraft's orbit around Mercury was highly eccentric, drifting between 200 and 500 kilometers (124 to 311 miles) above Mercury's surface at closest approach, and between 15,200 and 14,900 kilometers (9,445 to 9,258 miles) above the surface at its farthest point, and completing an orbit every 12 hours. Spacecraft operators at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, conducted several spacecraft maneuvers to counter the perturbing forces that caused MESSENGER's lowest orbital altitude to drift upward, away from its preferred observing geometry, and early in MESSENGER's First Extended Mission conducted a pair of maneuvers to reduce the orbital period to eight hours.