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Opportunity lands on Mars
Spirit 'upgraded from critical to serious'
Sunday, January 25, 2004 Posted: 1:11 AM EST (0611 GMT)

This white oval shows the location of Opportunity's landing site.

PASADENA, California (CNN) -- Opportunity, the second of NASA's twin rovers, has made the descent to the surface of Mars, touching down successfully at 0505 GMT Sunday (12:05 a.m. ET).

NASA now has two rovers on the ground, after Spirit landed on the red planet exactly three weeks ago on January 3. Though Spirit's landing was near perfect, the rover mission has had serious complications in recent days.

"We're on Mars everybody," mission scientist Wayne Lee declared as fellow members monitoring the landing at NASA's Jet Propulsion Laboratory burst into wild applause .

Dampened by the problems with Spirit, it had been a nervous few moments at mission control as NASA officials counted down and checked off the various descent maneuvers during what appeared to be a flawless six-minute sequence.

As planned, the airbag-encased craft bounced on the Martian surface and rolled gently for a few minutes before coming to a complete stop upside down.

NASA was awaiting further signals and communications from Opportunity, including images of the landing site.

There were "no fault tones" detected in the radio signals back to Earth, suggesting that the spacecraft arrived in good shape on Mars, a mission control official said.

Moments after the landing, California Gov. Arnold Schwarzenegger and former Vice President Al Gore walked through mission control to congratulate the workers there.

Opportunity is an exact replica of Spirit but was programmed to land about 6,600 miles (10,620 km) away on the opposite side of the planet, in an area known as the Meridiani Planum -- a smooth plain near Mars' equator, believed to be full of iron-bearing hematite.

The semi-precious mineral usually forms on Earth in the presence of liquid water -- leading scientists to think that water once flowed there.

The area is believed to be quite different from the reddish soil of Gusev Crater, where Spirit landed earlier this month.

Opportunity's site makes the landing more difficult than Spirit's, mission manager Jim Erickson said.

It is also the highest altitude landing by NASA on Mars.

In addition, Mars' increased distance from Earth would lengthen the time needed to communicate with the spacecraft.

Troubles with Spirit

The Mars rover Spirit is shown in this NASA drawing.
The Mars rover Spirit is shown in this NASA drawing.

Scientists are hoping the rover won't have the same problems that have hit Spirit this week.

That rover was set to use its tools to examine a nearby boulder when NASA lost contact with the vehicle.

But NASA engineers found a work-around Saturday for Spirit's problems, re-established communication and regained the ability to control it.

"This is very good news," project manager Pete Theisinger told reporters.

Spirit's condition, Theisinger said, "has been upgraded from critical to serious."

The rover is probably "three weeks away from driving," he said, as engineers study the problems and try to correct them with additional work-arounds in the meantime.

NASA engineers are working to trace the source of the problem as it could have implications on Opportunity's mission.

Spirit uses Flash memory to communicate with the flight software to establish a file structure and will shut itself down if the process is interrupted, Theisinger said.

Engineers guessed that Spirit's troubles were in its Flash memory and set about sending the rover a complex series of instructions to see if they could get it to bypass the corrupted memory.

Theisinger said engineers sent Spirit a command just before its daily "waking up," telling it to shut down and restart in what is known as "cripple mode," using RAM instead of Flash for its start-up instructions.

"That is precisely what happened," Theisinger said, and Spirit then sent an hour's worth of data back to Pasadena.

"Something in the flight software talking to the Flash memory is causing us difficulty," Theisinger said.

He said engineers did not know caused the problem, but if it is purely a software problem, it is likely fixable. If, however, a problem in the hardware is affecting the software, repair may not be possible.

But, "we have a vehicle that is stable now," he said.

PASADENA, Calif. -- Mars has received a one-two exploration punch as the second Rover -- Opportunity -- achieved a successful landing tonight on the red planet.

Engineers and scientists broke out in cheers and tears here at the Jet Propulsion Laboratory (JPL), mission control for the Mars Exploration Rover (MER) program.

Opportunity landed in the Meridiani Planum region of Mars. The spacecraft's exact whereabouts are not precisely known, but appears to have touched down within a pre-determined ellipse within Meridiani Planum.

Opportunity Landing Is Near-Perfect

Opportunity looks to have completed a near-perfect entry, descent, and landing.

Initial data suggested that the spacecraft hit Mars' surface at a relatively slow velocity -- some two to three times the force of gravity. The airbag system is designed to sustain a 40 g's collision with Mars.

Indications are that after coming to a stop, Opportunity was "side-petal" down. That means it will have to right itself on the red planet, then deflate its airbags.

The spacecraft slammed into the top of Mars' atmosphere at about 12,000 miles per hour (5.4 kilometers per second). That event was followed by a series of death-defying entry, descent and landing events.

Taking all of six minutes to plummet to the martian landscape, Opportunity bounced across Mars wrapped in its cocoon of airbags before coming to a complete stop.

"We're on Mars everybody. We're getting a strong signal," said Rob Manning, JPL's Entry, Descent and Landing manager.

Perfect maneuvering

Opportunity landed on Mars at 12:05 a.m. Sunday EST or 9:05 p.m. Saturday PST.Early today, mission managers chose not to use an option for making a final tweak to Opportunity's flight path. Previously, as the spacecraft closed in on the planet, the third and fifth out of five scheduled maneuvers were skipped as unnecessary. 

Getting to the exact entry point using only three maneuvers since Opportunity's launch was heralded early this morning by JPL's Louis D'Amario, navigation team chief for the Mars rovers.

Hematite-rich territory

The rover's main task is to explore the Meridiani Planum landing site and determine whether that region could have had a past environment that was watery and possibly suitable for sustaining life.

Opportunity is on the lookout for a gray hematite. Meridiani Planum has been found by orbiting spacecraft sensors to be rich in gray hematite. This type of iron oxide usually forms in association with liquid water.

Here at JPL, as Opportunity reached Mars, troubleshooting teams are working around-the-clock to get the Spirit Mars Exploration Rover back on line. It landed three weeks ago, but subsequently ran into an apparent computer glitch that halted its science gathering duties.