Final Braking Maneuver Friday At 1624 EST

Earlier this week, NASA's Mars Reconnaissance Orbiter began its final approach to the red planet after activating a sequence of commands designed to get the spacecraft successfully into orbit. But the ultimate test will come on Friday, March 10.

The approach sequence -- which began Tuesday -- will culminate Friday afternoon with the firing of the craft's main thrusters for about 27 minutes -- putting "a foot on the brakes," in the words of Guy Webster with JPL -- and reducing velocity by about 20 percent as the spacecraft swings around Mars at about 5,000 meters per second. That's about 11,000 miles per hour.

Mission controllers at NASA's Jet Propulsion Laboratory, Pasadena, CA and Lockheed Martin Space Systems in Denver, CO are monitoring the events closely.

"We have been preparing for years for the critical events the spacecraft must execute on Friday," said JPL's Jim Graf, project manager.  "By all indications, we're in great shape to succeed, but Mars has taught us never to get overconfident. Two of the last four orbiters NASA sent to Mars did not survive final approach."

Mars Reconnaissance Orbiter will build upon discoveries by five successful robots currently active at Mars: NASA rovers Spirit and Opportunity, NASA orbiters Mars Global Surveyor and Mars Odyssey, and the European Space Agency's Mars Express orbiter. It will examine Mars' surface, atmosphere and underground layers in great detail from a low orbit. It will aid future missions by scouting possible landing sites and relaying communications. It will send home up to 10 times as much data per minute as any previous Mars mission.

But first, it must get into orbit -- and that's no easy task. The necessary thruster burn will begin shortly after 4:24 pm PST on Friday -- with the last third of the expected 27-minute burn occurring in the shadow of Mars, outside of contact with Earth. Scientists won't be certain of its success for approximately 30 minutes after loss of radio contact.

Engineers designed the burn to slow the spacecraft just enough for Mars' gravity to capture it into a very elongated elliptical orbit. Once there, a six-month period of more than 500 carefully calculated dips into Mars' atmosphere -- a process called aerobraking -- will use friction with the atmosphere to gradually shrink the orbit to the size and nearly-circular shape chosen for most advantageous use of the six onboard science instruments.

"Our primary science phase won't begin until November, but we'll actually be studying the changeable structure of Mars' atmosphere by sensing the density of the atmosphere at different altitudes each time we fly through it during aerobraking," said JPL's Dr. Richard Zurek, project scientist for the mission.

Aero-News will bring you Real Time coverage Friday, as the Mars Reconnaissance Orbiter undergoes its most critical test yet. Stay tuned...

FMI: www.nasa.gov/mro