[meteorite-list] Second of Four Planned Maneuvers Extends MESSENGER Orbital Operations

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Sun, 14 Sep 2014 20:15:22 -0700 (PDT)
Message-ID: <201409150315.s8F3FMNO019548_at_zagami.jpl.nasa.gov>


MESSENGER Mission News
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 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.

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 17, 2011 (March 18, 2011 UTC), 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 Sun 14 Sep 2014 11:15:22 PM PDT

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