[meteorite-list] Planned Maneuver Further Extends MESSENGER Orbital Operations
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 3 Apr 2015 10:00:11 -0700 (PDT)
MESSENGER Mission News
April 3, 2015
Planned Maneuver Further Extends MESSENGER Orbital Operations
MESSENGER mission controllers at the Johns Hopkins University Applied
Physics Laboratory (APL) in Laurel, Md., conducted a maneuver yesterday
to raise the spacecraft's minimum altitude sufficiently to extend orbital
operations and further delay the probe's inevitable impact onto Mercury's
The previous maneuver, completed on March 18, raised MESSENGER to an altitude
at closest approach from 11.6 kilometers (7.2 miles) to 34.4 kilometers
(21.4 miles) above the planet's surface. Because of progressive changes
to the orbit over time in response to the gravitational pull of the Sun,
the spacecraft's minimum altitude continued to decrease.
At the time of yesterday's maneuver, MESSENGER was in an orbit with a
closest approach of 5.5 kilometers (3.4 miles) above the surface of Mercury.
With a velocity change of 2.96 meters per second (6.63 miles per hour),
four of the spacecraft's 12 smallest monopropellant thrusters nudged the
spacecraft to an orbit with a closest approach altitude of 27.5 kilometers
(17.1 miles). This maneuver also increased the spacecraft's speed relative
to Mercury at the maximum distance from Mercury, adding about 1.2 minutes
to the spacecraft's eight-hour, 17.6-minute orbit period.
The second orbit-correction maneuver (OCM) in MESSENGER's low-altitude
hover campaign, also called the extension of the second extended mission,
OCM-14 is the first propulsive course correction since December 2006 to
use the two small thrusters that point sunward from the sunshade center
panel. This view shows MESSENGER's orientation at the start of the maneuver.
MESSENGER was 200.6 million kilometers (124.6 million miles) from Earth
when the 6.7-minute maneuver began at about 4:30 p.m. EDT. Mission controllers
at APL verified the start of the maneuver 11.2 minutes later, after the
first signals indicating spacecraft thruster activity reached NASA's Deep
Space Network tracking station in Goldstone, Calif. The next maneuver,
on April 6, will again raise the spacecraft's minimum altitude, allowing
scientists to continue to collect images and data from MESSENGER's instruments.
The 3.8 days between OCM-14 and OCM-15 will be the shortest time between
any two MESSENGER maneuvers.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging)
is a NASA-sponsored scientific investigation of the planet Mercury and
the first space mission designed to orbit the planet closest to the Sun.
The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit
about Mercury on March 18, 2011, to begin a yearlong study of its target
planet. MESSENGER's first extended mission began on March 18, 2012, and
ended one year later. MESSENGER is now in a second extended mission, which
is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director
of Columbia University's Lamont-Doherty Earth Observatory, leads the mission
as Principal Investigator. The Johns Hopkins University Applied Physics
Laboratory built and operates the MESSENGER spacecraft and manages this
Discovery-class mission for NASA.
Received on Fri 03 Apr 2015 01:00:11 PM PDT