NASA scientists jubilant after Mars Odyssey arrives in orbit around Red Planet

PASADENA, Calif. (AP) _ NASA's 2001 Mars Odyssey spacecraft circled the Red Planet on Wednesday on its first full day in orbit, two years after the space agency suffered back-to-back failures by Mars

Wednesday, October 24th 2001, 12:00 am

By: News On 6

PASADENA, Calif. (AP) _ NASA's 2001 Mars Odyssey spacecraft circled the Red Planet on Wednesday on its first full day in orbit, two years after the space agency suffered back-to-back failures by Mars missions.

The craft fired its engine Tuesday night to slow its speed, then arced over Mars' north pole into orbit.

Odyssey arrived nearly directly on its target _ 480 miles above Mars' surface _ and is slowing moving away from the planet, said mission engineer Guy Beutelschies. No problems were reported.

``Everything went according to plan,'' Beutelschies said. ``We did a little bit better than we expected.''

The mission's initial success served as redemption for NASA after its earlier Mars missions failed.

``This embodies the American spirit. We showed we could win after being slammed a few times,'' said retiring NASA Administrator Daniel Goldin.

Odyssey's mission to study the makeup of Mars and to search for frozen reservoirs of water faced a critical step with the first and only firing of its engine. Failure could have sent the spacecraft hurtling past the planet.

Tension mounted at the Jet Propulsion Laboratory when the expected indication _ a change in a signal transmitted from the spacecraft _ was not detected as expected at 7:26 p.m. More than 4 minutes passed before the firing was confirmed.

``I was getting really worried then,'' project manager Matt Landano said.

Contact with Odyssey was lost as expected during its 20-minute pass behind the planet. Mission control erupted in cheers and high fives when the signal reappeared from across 93 million miles.

Early indications showed Odyssey was in an orbit circling Mars every 19 hours, Landano said. The spacecraft, which flew a six-month, 286 million-mile course to rendezvous with the Red Planet, had been targeted for an orbit of 20 hours or less.

``These guys really redeemed themselves,'' said Ed Weiler, NASA's associate administrator for space science. ``America needs some good news, especially now. Not many countries can do this and we showed that we could, right on the money.''

Odyssey's orbit will be adjusted to a circular route 250 miles above the surface by means of aerobraking _ dipping into the atmosphere in an around-the-clock process set to begin Friday. The spacecraft should settle into its final two-hour orbit by late January.

Arrival at Mars has been perilous for previous NASA missions.

Mars Observer disappeared as it neared the planet in 1993, probably due to a fuel system explosion. In 1999, a mix-up between English and metric units put the Climate Orbiter too close to Mars, causing it to burn up in the atmosphere. NASA's Polar Lander vanished three months later, probably due to a software error sending it crashing to the planet's surface.

Overall, fewer than one-third of the 30 missions launched to the planet by the United States and other countries since 1960 have succeeded.

The 1999 failures forced NASA to re-examine its processes and overhaul its ambitious plans for robotic missions to Mars.

``We were successful only because we had a failure last time,'' Goldin said. ``They checked and rechecked and the failure caused them to pay attention to things they had ignored before.''

NASA has continued to explore Mars from orbit via the Global Surveyor, which arrived in 1997 and has sent back thousands of detailed images.

Odyssey has instruments to map the distribution of minerals and search for water across the planet's surface. Liquid water is considered a necessary element for life; finding reservoirs could help determine whether life ever existed on Mars. Another instrument measures radiation and how that might endanger humans if they ever explore Mars.