Mars Orbiter Ready to Begin Engine Burn

BOULDER,Colorado - Ground controllers are ready to perform a major maneuver today of NASA'sMars Reconnaissance Orbiter (MRO)--an "end game" tactic that puts the orbiting probea step closer to scientific sensor sweeping of the red planet.

For months, the MRO has been aerobraking--using the friction of the planet'sthin atmosphere to slow the craft. That technique saves on onboard propellant.

Spacecraft engineers andnavigation experts are planning a burn today of MRO's Trajectory CorrectionManeuver (TCM) thrusters, said Wayne Sidney, MRO Flight Engineering Team Lead for Lockheed MartinSpace Systems, the firm that designed and built the spacecraft in neighboringDenver, Colorado.

"For regular burns up tothis point...over the last six months...they last on the order of seconds. This oneis going to last six minutes. It's a hefty burn," Sidney told SPACE.com."It's the biggest burn just with these TCM thrusters."

There's still more nudgingto do with MRO over the next few months, fine-tuning tweaks that push the probeinto a final, desired orbit. The mission's main science observations are scheduled to begin in November, after a period ofintermittent communications while Mars passes nearly behind the Sun.

Rock-solid, well behaved

Overall, MRO is inexcellent health, Sidney explained. However, one nagging item cropped up a fewweeks ago. A radio frequency switch to flip between MRO's high and low-gainantennas is stuck. A tiger team of experts is investigating the issue, tryingto ascertain the root, probable cause of the problem.

"If we don't get the switchunstuck we've lost some redundancy...but we still have the capability tocommunicate over the low and high-gain antennas using the other transmitter," Sidney explained. At this point in MRO's aerobraking campaign, "everything else has beenreally rock-solid, right on...and gone really well. It has been a remarkablespacecraft. Very well behaved," he added.

Dipping in and out of themartian atmosphere, MRO has seen very few surprises. A worry for aerobrakingspecialists is encountering dust storm activity that can mix things up in theatmosphere, playing havoc with the delicate, spacecraft-slowing maneuvers.

"The atmosphere has beenvery cold and clear the whole six months as we hoped it would be," Sidney said.

Science objectives

"Wejust made the decision to exit aerobraking today...on orbit 445," noted JamesGraf, MRO Project Manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. "This burn gets us out of the atmosphere. We have two more maneuversover the next two weeks before we are in the final orbit," he told SPACE.com.

Launched in August 2005,MRO swung into an elongated orbit around Mars in March of this year.

The $750 million MRO missionis designed to contribute to several science objectives: Determine whether lifeever arose on Mars; characterize the climate and geology of Mars; as well asprepare of eventual human exploration of the red planet.

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