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Mars Orbiter Successfully Makes Big Burn

BOULDER, Colorado - Groundcontrollers today successfully performed a major maneuver of NASA's MarsReconnaissance Orbiter (MOR)--an "end game" tactic that puts the orbiting probe a stepcloser to studying the red planet with its entire suite of science sensors.

Formonths, the MRO has been aerobraking--using thefriction of the planet's thin atmosphere to slow the craft. That techniquesaves on onboard propellant.

Thedecision to exit aerobraking was made early today, noted James Graf, MROProject Manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. The burn gets MRO out of the atmosphere, with two more maneuvers scheduled overthe next two weeks before the spacecraft achieves its science-gathering orbit,he told SPACE.com.

Spacecraftengineers and navigation experts exploited MRO's Trajectory Correction Maneuver(TCM) thrusters, said Wayne Sidney, MRO Flight Engineering Team Lead forLockheed Martin Space Systems, the firm that designed and built the spacecraftin neighboring Denver, Colorado.

Heavy lifting

"Iam greatly relieved that the aerobraking phase is over," Graf explained. "Allof aerobraking, but in particular the last demanding week, is dangerous and itis great to have it behind us."

Grafsaluted a combined JPL and Lockheed Martin Space Systems team that "performedfabulously over the last six months as did the spacecraft." With the heavylifting of aerobraking behind MRO operators, he said, the spacecraft team ismoving on into the transition phase events, which include the commissioning ofMRO instruments.

Thisupcoming phase has its own set of challenges for the team, Graf observed,including the deployment of the Shallow Subsurface Radar (SHARAD) antenna andthe lid for the Compact Reconnaissance Imaging Spectrometers for Mars (CRISM),he said.

"Theengineering images returned from these instruments at the end of the monthshould be astounding," Graf predicted.

Sidney told SPACE.comthat regular MRO burns over the last six months were on the order of seconds.The burn today lasted several minutes, he said, "the biggest burn just withthese TCM engines."

Theburn was executed on-time and performance was perfect, Sidney said. "Thespacecraft is in great shape. Aerobraking is now officially over."

There'sstill more nudging to do with MRO over the next few months, fine-tuning tweaksthat push the probe into a final, desired orbit. The mission's main scienceobservations are scheduled to begin in November, after a period of intermittentcommunications while Mars passes nearly behind the Sun.

Rock-solid, well behaved

Overall,MRO is in excellent health, Sidney explained. However, one nagging item croppedup a few weeks ago. A radio frequency switch to flip between MRO's high andlow-gain antennas is stuck. A tiger team of experts is investigating the issue,trying to ascertain the root, probable cause of the problem.

"Ifwe don't get the switch unstuck we've lost some redundancy...but we still havethe capability to communicate over the low and high-gain antennas using theother transmitter," Sidney explained. At this point in MRO's aerobrakingcampaign, "everything else has been really rock-solid, right on...and gone reallywell. It has been a remarkable spacecraft. Very well behaved," he added.

Dippingin and out of the martian atmosphere, MRO has seen very few surprises. A worryfor aerobraking specialists is encountering dust storm activity that can mixthings up in the atmosphere, playing havoc with the delicate,spacecraft-slowing maneuvers.

"Theatmosphere has been very cold and clear the whole six months as we hoped itwould be," Sidney said.

Launchedin August 2005, MRO swung into an elongated orbit around Mars in March of thisyear.

The$750 million MRO mission is designed to contribute to several scienceobjectives: Determine whether life ever arose on Mars; characterize the climateand geology of Mars; as well as prepare of eventual human exploration of thered planet.

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