Moment Of Truth: Spirit Set for Mars Landing Tonight

PASADENA, California -- It is nail biting time for scientists and engineers here at the Jet Propulsion Laboratory (JPL), the home of twin Mars rovers built to open a new chapter in the exploration of the Red Planet.

Two NASA (news - web sites) Mars landers -- Spirit and Opportunity -- are speeding toward "sweet spot" touch down sites at different, but scientifically attractive locations on Earth's mysterious neighbor.

The opening act in this $820 million drama to place dual robot geologists on Mars is the landing of the Mars Exploration Rover (MER) dubbed Spirit tonight at about 8:35 p.m. Pacific Standard Time (PST).

The target: Gusev Crater -- a possible former lake in a giant impact crater on Mars. Primary among the mission's scientific goals is to search for and characterize a wide range of rocks and soils that hold clues to past water activity on Mars

A final decision on a last fine-tuning of Spirits trajectory into Gusev Crater is to be made here this afternoon, although doing so is considered unlikely. Navigators at JPL are highly pleased with the spacecrafts trajectory as it closes in on Mars and plunges toward its pre-selected landing zone.

After years of construction and testing, and months of travel through the coldness of interplanetary space, Spirit will undergo a literal "trial by fire" as it makes a heated entry into the Martian atmosphere.

Following a quick succession of steps to slow down, Spirit must then survive a high-speed head-on collision with Mars. The six-wheeled rover is protected by large airbags sturdy enough to "rock on" as it repeatedly bounds across Mars' boulder and crater-pocked surface at freeway speeds after landing.

Edward Weiler, NASA Associate Administrator for Space Science, said that whether or not Spirit had safely put down on Mars surface should be obvious no later than late Sunday night. "We wont drag this out for weeksas it would impede our ability to prepare for (the landing of MER) Opportunity 21 days later," he said during a Friday press briefing here.

"To me this moment in time is like a dream come true," said James Garvin, Mars Exploration Program Scientist at NASA Headquarters in Washington, D.C.

"Three years ago we began with little more than a vision, guided by science, and here we are doing it," Garvin told SPACE.com .

Garvin said that with the two rovers, along with Europes Mars Express mission joining up with the veteran Mars Global Surveyor and Mars Odyssey spacecraft circling Mars -- all exploring the planet together -- "what could be better," he said.

Several key officials in the Mars Exploration Rover program took part in the Mars Pathfinder mission that unleashed the small robot rover -- Sojourner -- that successfully wheeled across the planet in 1997.

Among them is Joy Crisp, JPLs Mars Exploration Rover project scientist. In contrasting the two programs, she underscored the much larger number of individuals working on Spirit and Opportunity.

The time pressure in readying the twin rovers, along with so many people involved did complicate the ability for everyone on the project to communicate with each other, Crisp said.

"We did a lot more documentation on this project than Pathfinder," Crisp said. As for Spirit and Opportunity teams being ready for the assault on Mars, she added: "You are torn. Sometimes you wish you had more time to get ready. Other times you think, lets just get it done."

Another Mars Pathfinder/Sojourner veteran is JPLs Matthew Golombek, now Mars Exploration Program landing site scientist.

Does landing on Mars become easier given his earlier Mars Pathfinder/Sojourner experience?

"Each one is different. Im ready for it and I am excited. This is a much bigger project. The landing site selection was a beast compared to Pathfinder. We had so much more information," Golombek told SPACE.com .

"Theres so many options hereso many things that can happen. And theres no way to know what can happen," Golombek said. "I just hope Im super, super, super busy."

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(I'll post this here rather than start a new thread.)

Nasa probe set for Mars landing as Beagle's handlers carry on listening

By Steve Connor, Science Editor
The Independent (UK)
04 January 2004

After sending a spacecraft on a journey of 300 million miles to Mars, scientists at the US National Aeronautics and Space Administration (Nasa) could wake up today with an awful feeling of déjà vu.

If all goes according to plan, the first of a pair of robot landers should have arrived safely on the surface of the Red Planet in the early hours of this morning.

Nasa will be hoping its lander is more successful than Britain's Martian explorer, Beagle 2, which went missing on Christmas Day.

The best new hope of contacting Beagle 2 will also come today when the orbit of its mother ship, Mars Express, finally comes close to the probe's presumed landing site. Beagle 2 should by now be transmitting a continuous SOS during daylight hours, rather than the intermittent pulses controlled by its computer clock. If its transmitter is working, then Mars Express should be able to hear it.

Scientists believe there will be even better opportunities for contact in about two days' time when the orbiter is due to fly directly over the landing site. Their biggest fear is that it has crashed or landed in a crater or crevice, thus making it unable to open its solar panels and transmit any signals.

Although Beagle 2 and Nasa's Mer mission share much in common in terms of measures designed to ensure a soft landing, such as heat shields, parachutes and a set of inflatable gas bags, the similarities mask a very different approach to the technical and engineering challenges of putting a space probe safely on the Martian surface.

Nasa spent $820m (£512m) on the Mer mission, whereas the European Space Agency's total budget for the Mars Express orbiter was just over £100m, and a relatively paltry £45m for the Beagle 2 lander.

The British designers had to cope with a pitifully small payload of 65kg for the Beagle 2 hardware, while their US counterparts had the luxury of playing with a payload of 365kg for the Mer lander.

In addition to parachutes and gas bags, the Mer had rocket boosters to slow down its descent and cameras to gauge the spacecraft's horizontal velocity before landing.

It also employed a complex programme of radio call signs to its controllers on Earth during landing, while Beagle 2 had to land in radio silence.

Even if it did land successfully, Beagle 2 could only operate beyond the landing site with a Heath Robinsonesque "mole'', a hollow tube containing a spring-loaded weight. Mer has a six-wheel-drive vehicle called Spirit, which is about the size of a golf buggy.

Beagle 2 is nevertheless capable of carrying out an analysis of Martian rocks that equals or even surpasses its American cousin. Professor Colin Pillinger of the Open University said that Beagle 2 was the only probe designed specifically to search for the direct signs of life, rather than indirect evidence, such as the presence of water.

Whereas Spirit will look for the geological signs that water once flowed on Mars, Beagle 2 has the theoretical power to detect directly the chemical signature of microscopic fossils that may have been preserved for billions of years.

But the relative merits of the scientific instruments on board the two Martian landers mean nothing unless the probes can communicate what they find. Beagle 2's day looks as if it may soon be declared over before it ever began; now it is the chance of Spirit to steal the Martian limelight.

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