The pieces are coming together for NASA’s next Mars mission, a reconnaissance satellite designed to identify good prospective landing sites for future explorers.

The Mars Reconnaissance Orbiter (MRO) is set to be launched by a Lockheed Martin-built Atlas 5 rocket Aug. 10.

“It’s a real mixture of feelings,” MRO project manager James Graf said in an interview. “We’re elated that we’re ready to go launch, but white-knuckled hoping that everything will go as we expect.”

NASA researchers tout the MRO spacecraft as the largest orbiter aimed at Mars in the last 30 years. Standing about six meters tall and spanning 13 meters wide, it is larger than the agency’s other red planet orbiters, Mars Global Surveyor and Mars Odyssey. The orbiter weighs about 2,180 kilograms, but came in about 51 kilograms underweight, allowing engineers to add propellant that should extend its flight lifetime out to about 2014.

“This is a big mission for us,” said Doug McCuistion, director of NASA’s Mars Exploration Program at the agency’s Science Mission Directorate, in a preflight press briefing. “It’s the most powerful suite of instruments ever sent to another planet.”

MRO will carry a hefty science payload to Mars, with six instruments designed to track martian weather, resolve objects the size of a kitchen table and measure the planet’s composition and atmospheric structure with more detail than ever before.

“The MRO spacecraft is many things,” said Richard Zurek, the mission’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “It’s a weather satellite, it’s a geological surveyor and it’s a scout for future missions.”

The MRO is expected to be the vanguard for two landers NASA plans to launch toward Mars in the next five years, and will identify potential landing targets. The Phoenix lander currently is scheduled to launch in August 2007 and touchdown in the planet’s polar region. A large rover, the Mars Science Laboratory, is expected to launch in late 2009.

To prepare for those missions, MRO carries three cameras, one spectrometer, a climate sounder and subsurface radar, all designed to shed new light on the structure and composition of Mars.

MRO’s High-Resolution Imaging Science Experiment will photograph Mars’ surface with such detail that researchers expect to resolve objects as small as 1.3 meters wide. To get a wider view, the orbiter’s Context Camera will gather images about 40 kilometers across, with a resolution of about eight kilometers per pixel.

A third camera, the Mars Color Imager, is expected to generate a global map of martian weather and track large-scale dust storms, day-to-day weather conditions, as well as atmospheric and polar cap changes.

“Each day we will build up a full weather map of Mars,” Zulek said of the Mars Color Imager. “And [the camera] is the size of a hand.”

MRO’s Compact Reconnaissance Imaging Spectrometer for Mars will observe the red planet in the visible and infrared range to pick out minerals and other materials that may have formed in water or wet conditions in the planet’s past.

The Mars Climate Sounder, an instrument designed to study the changes in Mars’ atmospheric composition and temperature according to its height, is expected to take measurements every five kilometers between space and the martian surface.

Finally, a shallow subsurface radar — similar but smaller to one that rides aboard Europe’s Mars Express probe — will search for underground water down to one kilometer beneath the martian soil. The Mars Advanced Radar for Subsurface and Ionosphere Sounding aboard Mars Express, on the other hand, will look deeper, probing as deep as five kilometers beneath Mars’ surface.

“The radar profile will build up a 3D view of Mars,” Zulek said.

Before the MRO spacecraft can cull secrets from the red planet, it must first leave its home world.

After launch, it should take MRO about six months to reach Mars, then another seven months or so to adjust its eccentric orbit into a 400-kilometer high circle. The orbiter will use aerobraking to adjust its orbit, swooping in close to Mars and using the atmosphere to slow the spacecraft.

Engineers are taking care not to damage any of MRO’s components during the integration with its launch vehicle, including the spacecraft’s massive solar arrays.

“These are the biggest solar arrays ever sent to another planet,” Graf said.

Craig Calvin, an MRO systems engineer for Lockheed Martin, said the orbiter’s solar panels span a total of about 20 square meters and carry about 7,000 solar cells. All those cells are needed to generate the five kilowatts of power in Earth orbit, though that power output will diminish to about two kilowatts at Mars, Calvin said, adding that MRO’s instruments only require one kilowatt to function.