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.
Martian atmospherics
At a Saturday afternoon press briefing, Mark Adler, Deputy Mission Manager for the Mars Exploration Rover (MER) program said the last trajectory course change for Spirit had been cancelled earlier today.
"Right now, the spacecrafts health is excellent," Adler noted.
Spirit has been uploaded with the software smarts to conduct the sequence of vital entry, descent, and landing events, Adler said. A dust storm on the other side of the planet, he added, has altered the atmospheric density over the Gusev Crater landing site, with ground controllers making a small adjustment in the timing of Spirits parachute deployment.
Adler said that due to the dust-driven density change -- actually making the atmosphere thinner -- the parachute will be deployed three or four seconds earlier than originally planned.
According to Louis DAmario, MER Navigation Team Chief, Spirits is headed for a bulls-eye landing. "Its truly excellentbetter than we could have possibly hoped for. Its essentially perfect navigation," he reported.
Trial by fire
Rob Manning, MER Project Entry, Descent and Landing Lead, said the spacecraft is ready for its rough and tumble touch down at Gusev Crater, wrapped inside protective airbags. "This is like an athlete that wants to perform in the Olympics," he said.
"Were very confident that the airbags are going to do a great job," Manning said.
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.
Guided by science
"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.
Time pressure
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."
So many things can happen
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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