NASA MESSENGER Mission News August 24, 2004

MESSENGER’s Mission Operations Team Successfully Completes Mission’s
First Trajectory Correction Maneuver

MESSENGER completed its first planned maneuver today at 5:03:35
p.m., EDT, when the thrusters ignited to correct trajectory
inaccuracies associated with launch. The spacecraft’s four medium (5-
pound) hydrazine-propellant thrusters did the brunt of the work with
only minor tweaks needed from eight of the 12 small (1-pound)
thrusters. It took only 26 seconds for a tracking station in Madrid,
Spain, to pick up signals indicating the maneuver had begun.

“It was a beautiful maneuver with all maneuver commands executing as
they were supposed to,” says Mission Operations Manager Mark
Holdridge. The 3.6-minute thruster burn cut the spacecraft’s
velocity by 40 mph (18 meters per second) relative to the sun and
slowed the spacecraft to a mere 63,990 mph. MESSENGER is now 4.8
million miles from Earth.

On Aug. 27, testing of instruments and subsystems will resume, with
the back-up processor (DPU-B) being used to turn on the instruments
as a test of its viability. Two more small maneuvers later this year
(Sept. 24 and Nov. 19) are needed to precisely target the spacecraft
for its August 2005 Earth swingby.

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and
Ranging) is a scientific investigation of the planet Mercury, and
the first NASA mission designed to orbit the planet closest to the
Sun. Dr. Sean C. Solomon, of the Carnegie Institution of Washington,
leads the mission as principal investigator. The Johns Hopkins
University Applied Physics Laboratory in Laurel, Maryland, built and
will operate the MESSENGER spacecraft and manages the Discovery-
class mission for NASA.