NASA's Mars Reconnaissance Orbiter is set to arrive at the red planet Friday after a seven-month trip from Earth.

The largest orbiter sent to Mars in 30 years by NASA, the MRO spacecraft launched on Aug. 12, 2005 with six primary instruments to study the Martian surface, atmosphere and potential underground water and ice deposits. Armed with what's billed as the most powerful camera ever sent to another planet, MRO is expected pick out choice landing spots for future Mars-bound spacecraft and may even solve the mystery of a lost 1999 lander in the process.

Here's a handy primer on NASA's MRO spacecraft, its mission and its road to Mars.


10 Crowded Martian Neighborhood

The Mars Reconnaissance Orbiter (MRO) is a latecomer to what is arguably a bustling robotic neighborhood on and around the red planet.

The $450-million MRO probe will become the fourth operational orbiter around Mars and the sixth overall spacecraft to study the planet simultaneously. NASA's twin Mars rovers are rolling across the planet's surface, while its Mars Odyssey, Mars Global Surveyor and Europe's Mars Express scan the world from orbit.

9) Double Role

MRO's initial mission is a two-year assignment to scan for evidence of past or present water while conducting a comprehensive survey of the planet's surface and atmosphere. But the job doesn't end there.

After completing its primary mission, MRO is expected to use its large antenna (seen in this preflight image) to serve as an interplanetary phone operator, relaying data and instructions between flight controllers on Earth and future landers and rovers on Mars. The entire mission carries a $720 million cost.

8) Subsurface Water Radar


Like the European Space Agency's Mars Express, MRO sports its own radar tool to probe for ice or liquid water buried beneath the Martian surface.

The NASA probe's Shallow Subsurface Radar (SHARAD) is expected to ping the planet in 85-millisecond bursts of radar and penetrate up sixth-tenths of a mile (one kilometer) beneath the surface - actual depth depends on the Martian upper crust. In addition to isolating potential water pockets, the tool will record the different rock layers of Mars for geologists to study.

7) Martian Weather

Researchers are eager for MRO's look at Martian weather patterns. After all, Martian winds and dust devils scrubbed the solar arrays of NASA's Spirit and Opportunity clean during their mission, allowing them to draw more power than expected and lengthen their lifetimes.

MRO's Mars Color Imager (MARCI), with its horizon-to-horizon range, is designed to record daily weather maps, while the Mars Climate Sounder will study the structure of the planet's atmosphere.

6) All Eyes on Mars

MRO carries three cameras and a spectrometer to build a comprehensive picture of the Martian surface. Its HiRISE camera will take a close look at the specific features, while the probe's Context Camera will record strips of terrain more than 18 miles (30 kilometers) wide. The fish-eyed MARCI is expected to provide global coverage and track minute changes in the atmosphere and surface.

Capping the package is the CRIS spectrometer, which will hunt for water-related minerals and determine the composition of the Martian surface in areas as small as a house with an accuracy about 10 times sharper than any other tool placed in Mars orbit. MRO will also demonstrate an optical navigation camera that may be used for future missions.

5) Glutton for Data

It may be a technical matter, but MRO's ability to beam data home is no small feat. The spacecraft's 10-foot (three-meter) antenna is expected to transmit about 34 terabits of data. How much information is that? It's three times the amount sent home by NASA's Cassini, Deep Space 1, Magellan, Mars Odyssey and Mars Global Surveyor missions combined.

The electrical power feeding MRO's antenna - and its extensive instrument package - stems from two of the largest solar arrays ever to fly. Made up of 7,000 solar cells and spanning 220 square feet (20 square meters), the arrays generate about twice as much power - two kilowatts at Mars - than required, spacecraft engineers have said.  

4) Landing Site Recon

A chief goal of the MRO mission is to pick out the best sites for future red planet surface probes like the Mars Science Laboratory (seen here) and Phoenix lander. Orbital data, for example, used imagery to find the Gusev Crater landing spot for NASA's Spirit rover, while space-based mineral studies pointed to the Meridiani Planum region for Opportunity.

MRO's suit of cameras, radar and spectrometers make it a prime instrument in deciding where landers may have the most success learning about Mars' watery past or hints that the planet may have once been capable of supporting life.

3) Pinpointing Liquid Water Effects

With MRO's science instruments working together, researchers hope to track all available water-related source and signals at or under Mars.

Scientists consider water a key ingredient for life on Earth, and are eager to find underground caches of it at Mars. Should they be found, such reservoirs could be key in determining whether the planet could support life - if only mere microbes clustered around subsurface hot springs - today or in the distant past.

2) HiRISE Hunt for Mars Polar Lander

MRO's High-Resolution Imaging Science Experiment (HiRISE) camera, with its ability to resolve objects just three feet (one meter) across, may finally allow NASA's Mars Polar Lander to rest in peace.

The lander crashed in December of 1999 and repeated searches have turned up some possible targets, but nothing conclusive. With its sharp eye and low flight orbit - up to 199 miles (320 kilometers - MRO may be able to finally find the lost probe and put its location to rest.

1) Hit the Aerobrakes

Before NASA's MRO probe can begin any of its mission objectives, it has to slow down first.

The probe will rely on a relatively tried and true method called aerobraking, which takes advantage of the drag from a planet's atmosphere to shed the immense speed a probe builds up during transit and shape its orbit. But the process is not without risk. A navigation error sent NASA's Mars Climate Orbiter plunging into the Martian atmosphere before it could even enter orbit in 1999 and begin aerobraking, though the Mars Odyssey and Mars Global Surveyor orbiters used the method successfully.

MRO is expected to begin an estimated hundreds of aerobraking dips into Mars' atmosphere on March 30, ultimately shaving its initial, extremely elliptical orbit into a near-circular path by November 2006.