NASA Mars Probe on Target for Orbital Arrival
An artist's interpretation of MRO's orbit insertion burn at Mars on March 10, 2006.
Credit: NASA/JPL.

This story was updated at 1:15 p.m. EST.

With NASA's Mars Reconnaissance Orbiter just hours away from firing its engines to enter orbit around the red planet, scientists on Earth are on pins and needles waiting for the mission-critical event.

LIVE coverage of MRO's Mars arrival coverage begins at 3:30 p.m. EST. Click here.
"It's a little bit nerve-wracking, even though it's exciting," said Doug McCuistion, director of NASA's Mars exploration program during a mission briefing at the Jet Propulsion Laboratory in Pasadena, California Friday. "Today we're here to insert the most capable orbiter ever sent to another planet."

With its six science instruments and high-resolution cameras, MRO is expected to reveal more details about Mars' surface, atmosphere and water cycle than any previous mission to date. The spacecraft is right on target to ignite its engines just after 4:24 p.m. EST (2124 GMT) today during a 27-minute maneuver that, mission managers hope, will place the spacecraft orbit around Mars.

Orbital arrival is a critical time for any planetary expedition, where the slightest glitch or mistake can send the probe careening past the planet or plunging into its atmosphere.

"NASA has about an average grade of 'C' doing this," McCuistion said of orbit insertion maneuvers. "But these guys will do it. We've got a great team."

Robert Lock, lead mission manager for the orbiter at JPL, said MRO is right on track for today's orbit insretion maneuver. The spacecraft's flight path is so precise that two last minute maneuvers - one slated for this morning and the other for late yesterday - were unnecessary.

"We're very pleased that we're exactly on trajectory," Lock said.

MRO is about 33,000 miles (53,108 kilometers) from Mars and closing at about 7,000 miles per hour (11,265 kilometers per hour), though that speed should accelerate to 11,000 miles per hour (17,702 kilometers per hour) by the time of today's engine burn. Mission managers will only be in contact with the probe for the first 21 minutes of the 27-minute maneuver, leaving MRO to complete the burn itself while on the other side of Mars.

Ground tracking stations in Spain and California will be listening for MRO's signals as it swings out from behind Mars at about 5:16 p.m. EST (2216 GMT), though flight controllers will wait about 30 minutes to allow the orbiter to set itself to rights in case it encountered any glitches while out of range, mission managers said.

Final orbital arrival preparations begin about two hours before the planned engine burn, when flight controllers will direct MRO to pressurize its fuel tanks, they added.

Nothing to do but wait

While engineers and flight controllers prepare for MRO's Mars arrival, the mission's science teams awaits news that their probe survives the ordeal.

"For the science teams right now, this is a period of waiting," said MRO project scientist Richard Zurek during the briefing. "We've checked out the instruments during the cruise [and] made sure the cameras are in focus."

Larger than any of the three other orbiters currently studying Mars, NASA's $720 million MRO mission carries a hefty suite of science tools to study the red planet in unprecedented detail. The probe is expected to spend two years studying Mars and two more serving as a communications relay between the red planet and Earth for future spacecraft.

The 4,806-pound (2,180-kilogram) MRO probe is equipped with a six-instrument package that includes the ultra high-resolution HiRISE camera, a ground-penetrating radar and several other climate, atmosphere and surface scanning tools to tracking Mars' water history and pinpointing potential landing sites for future missions.

"It's the most technologically advanced payload that we've ever sent to another planet," said James Graf, NASA's MRO project manager at the Jet Propulsion Laboratory (JPL) in Pasadena, California, said in a March 8 mission update. "I think we're ready."

But MRO's arrival in Mars orbit is just the beginning of its pre-science phase.

The spacecraft is expected to enter a 35-hour orbit today that ranges from 350 miles (563 kilometers) to 27,000 miles (43,452 kilometers) in altitude above Mars. Over the next six months or so, the probe will dip into Mars' atmosphere about 550 times in process called aerobraking, which uses friction and drag with the planet's upper atmosphere to slow and shape its orbit.

Mission managers are targeting a final circular orbit about 190 miles (305 kilometers) above the Martian surface. MRO launched from Earth on Aug. 12, 2005 atop an Atlas 5 rocket and spent seven months flying to Mars.

"It's pretty exciting," NASA researcher Candice Hansen-Koharcheck, a science team member for MRO's HiRISE camera, said Thursday of the planned orbital arrival. "I am just going to be a basket of nerves."

NASA will broadcast MRO's Mars approach and orbital arrival live on NASA TV beginning at 3:30 p.m. EST.'s NASA TV feed is available here. You are welcome to follow MRO's arrival using's Mars Reconnaissance Orbiter mission special report by clicking here.