NASA's New Mars Orbiter Bears Down on Red Planet
This is an artist's concept of the Mars Reconnaissance Orbiter during its critical Mars Orbit Insertion process. In order to be captured into orbit around Mars, the spacecraft must conduct a 25-minute rocket burn when it is just shy of reaching the planet. As pictured, it will pass under the red planet's southern hemisphere as it begins the insertion. Image
Credit: NASA.

It's crunch time for NASA's Mars Reconnaissance Orbiter, a massive spacecraft bearing down on the red planet for a March 10 arrival after seven months of spaceflight.

The orbiter is set to fire its thrusters at 4:25 p.m. EST (2125 GMT) Friday in a maneuver that, researchers hope, will put MRO in orbit around Mars to study the planet's atmosphere, water history and identify landing sites for future missions.

"The mission is entering a very dangerous phase for the next several days," said Fuk Li, NASA's Mars exploration directorate chief at the Jet Propulsion Laboratory (JPL) in Pasadena, California. "We've sent four missions that we intended to orbit Mars [in 15 years] and only two have succeeded...for us those are sobering numbers."

MRO is expected to conduct a 27-minute thruster burn to place it in an elliptical orbit around Mars. Flight controllers will be in contact with the spacecraft for the maneuver's first 21 minutes before MRO swings behind the planet's southern hemisphere to complete the orbit insertion burn. The spacecraft is expected to reestablish contact with Earth at 5:16 p.m. EST (2216 GMT), mission managers said.

"For the last six minutes we are essentially in white knuckle time," said James Graf, MRO project manager at JPL, during a Wednesday press conference. "If we don't get several of those last minutes, we will not be able to get into Mars orbit."

But so far, the $720 million MRO mission has performed flawlessly.

The probe's 310-million mile (498-million kilometer) flight has been so precise since its Aug. 12, 2005 launch that flight controllers cancelled the last two of four planned course corrections, saving precious fuel for the orbiter's mission in Mars orbit, Graf said. Its Optical Navigation Camera, a new imager designed to compare Mars' two moons Phobos and Deimos with background stars to determine MRO's position, has already proven itself useful and achieved one of several technology demonstrations slated for the mission, he added.

MRO will join two other NASA orbiters - Mars Global Surveyor and Mars Odyssey - currently circling Mars, as well as the space agency's Spirit and Opportunity rovers crawling across the planet's surface. Europe's Mars Express probe is also orbiting the planet.

But MRO outstrips all three orbiters in size and camera resolution and is expected to lay the foundation for future Mars missions.

"We're bringing more capability to the planet," said Richard Zurek, MRO's project scientist at JPL, adding that the probe's science package will help researchers learn more of the water story on Mars. "What we're really doing now is establishing the background environment that we have to deal with when we plan future missions."

MRO carries six primary instruments to study Mars, including the High-Resolution Imaging Science Experiment (HiRISE) camera that can collect more data in a single image than NASA's twin Mars rovers sent home during their first 90 days, mission managers said.

During its two-year science mission, subsurface radar will probe for underground water and ice, while other instruments hunt for water-related minerals and study the Martian atmosphere. A suite of three cameras will also pick out potential landing sites for future spacecraft.

Normal science operations will begin this fall after MRO completes about seven months of aerobraking maneuvers, which use atmospheric drag to slow and shape the spacecraft's orbit, to reach its final orbit, mission managers said. The first of 550 aerobraking passes is scheduled for later this month, and each pass will allow researchers to map the density of the Martian atmosphere, they added.

"There are waves in the atmosphere just like there are waves in [Earth's] ocean," Zurek said. "Knowing about these variations helps us plan our aerobraking process."

NASA will broadcast a pre-orbit insertion MRO mission briefing on NASA TV at 12:00 p.m. EST (1700 GMT) on March 10. Live coverage of MRO's Mars arrival begins at 3:30 p.m. EST (2030 GMT). You are invited to follow the mission's progress via's NASA TV feed available here.