NASA spacecraft nearing Mars

A drawing of Mars Odyssey approaching the red planet

By Amanda Barnett
CNN

(CNN) -- Mars is about to get a new visitor. After a journey of 285 million miles (456 million kilometers), NASA's Mars Odyssey spacecraft is scheduled to enter orbit around the red planet on Tuesday.

"The spacecraft is right on course," said Bob Mase, the lead navigator for the mission.

Launched on April 7 from Cape Canaveral, Florida, the $300-million, 1.7-ton ship is slated to search for water, map surface minerals and measure radiation levels -- observations that could provide clues about possible extraterrestrial life. The probe will not land.

Odyssey will begin a critical engine burn to put it into orbit at 10:26 p.m. EDT on Tuesday. Engineers expect to lose the radio signal from the spacecraft as it goes behind Mars about 10 minutes after the burn begins.

"The next 20 minutes will likely be the longest 20 minutes of our lives," said Dave Spencer, Mars Odyssey mission manager at NASA's Jet Propulsion Laboratory in Pasadena, California.

"If all goes well, shortly before 8:00 p.m. (PDT) Odyssey should emerge from behind Mars and you'll see a lot of happy faces," said Spencer.

Spencer expects to know in a few hours whether the spacecraft made it to proper orbit about 250 miles (400 kilometers) above Mars.

The challenge of Mars

Odyssey will be the first spacecraft to arrive at Mars since two NASA spacecraft were lost. In September 1999, the Mars Climate Orbiter presumably burned up in the martian atmosphere because propulsion engineers failed to convert English and metric units.

Three months later, its sibling spacecraft, the Mars Polar Lander, likely crashed because a software glitch shut off the descent engines prematurely, sending it on a fatal plunge.

"This is a tremendous challenge and many Mars missions in the past have faced challenges," Jim Garvin, NASA's lead Mars scientist.

According to NASA, of the 30 missions sent to Mars by three countries over 40 years, fewer than one-third have been successful. But Garvin said he feels the public understands how difficult it is to operate spacecraft in deep space and added that all systems look good for Odyssey.

"We are very confident and excited about this mission," he said at a briefing on Thursday.

Odyssey has had a problem with one of its science instruments.

A radiation detector called MARIE (Martian Radiation Environment Experiment) locked up on August 13 after engineers commanded it to downlink data. NASA will send up commands to try to restart the instrument after Odyssey safely is in orbit.

A joint odyssey

Odyssey won't be alone in monitoring Mars. It will join another satellite, Mars Global Surveyor, which has been circling Mars since 1997, snapping hundreds of thousands of high-resolution pictures.

Surveyor's camera can spot details as small as 3 meters. The camera onboard Odyssey cannot focus as well, but it will have the ability to "see" much more than physical topography.

The new orbiter is equipped with an infrared imaging camera that can distinguish the mineral content of geologic features only 110 yards (100 meters) across, compared to 1.9 miles (3 kilometers) for a similar instrument on the Mars Global Surveyor.