September 12, 2014
Second of Four Planned Maneuvers Extends MESSENGER Orbital Operations
MESSENGER mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., conducted the second of four maneuvers designed to raise the spacecraft’s minimum altitude sufficiently to extend orbital operations and delay the probe’s inevitable impact onto Mercury’s surface until early next spring.
The first of the four maneuvers, completed on June 17, raised MESSENGER to an altitude at closest approach from 115.0 kilometers (71.4 miles) to 156.4 kilometers (97.2 miles) above the planet’s surface. Because of progressive changes to the orbit over time, the spacecraft’s minimum altitude continued to decrease.
At the time of this most recent maneuver, MESSENGER was in an orbit with a closest approach of 24.3 kilometers (15.1 miles) above the surface of Mercury. With a velocity change of 8.57 meters per second (19.17 miles per hour), the spacecraft’s four largest monopropellant thrusters (with a small contribution from four of the 12 smallest monopropellant thrusters) nudged the spacecraft to an orbit with a closest approach altitude of 94 kilometers (58.4 miles). This maneuver also increased the spacecraft’s speed relative to Mercury at the maximum distance from Mercury, adding about 3.2 minutes to the spacecraft’s eight-hour, two-minute orbit period. This view shows MESSENGER’s orientation soon after the start of the maneuver.
MESSENGER was 166.2 million kilometers (103.27 million miles) from Earth when the 2-minute, 15-second maneuver began at 11:55 a.m. EDT. Mission controllers at APL verified the start of the maneuver 9.2 minutes later, after the first signals indicating spacecraft thruster activity reached NASA’s Deep Space Network tracking station outside of Madrid, Spain.
Two more maneuvers, on October 24, 2014, and January 21, 2015, will again raise the spacecraft’s minimum altitude, allowing scientists to continue to collect images and data from MESSENGER’s instruments.
Media contact: Paulette Campbell, 240-228-6792, Paulette.Campbell@jhuapl.edu