Spirit's twin, Opportunity, is also on course and will reach Mars three weeks later.
Akin to making a "hole in one" after Spirit has flown over millions of miles, ground control team members at JPL want to make a bulls-eye landing within Gusev Crater, a 90-mile (145-kilometer) wide feature likely formed three to four billion years ago as a result of an impacting asteroid.
Gusev is considered a dry and ancient lakebed, complete with a channel system that most probably carried liquid water, or water and ice, into the crater.
Spirit in the sky
The Gusev landscape has been eyed for years by Nathalie Cabrol, a planetary scientist at NASAs Ames Research Center. She was a key advocate for having a Mars Exploration Rover touch down at Gusev, and eagerly awaits the first "ground level" panorama from Spirits camera.
"Yes, this is getting very close now," Cabrol told SPACE.com . "At the present timeinterestingly enough, I am not nervous at all. I guess, there is nothing we can do except pray!"
"I find myself often thinking how big Mars should be by now in Spirit's eyes and it is a wonderful thing to be thinking about," Cabrol said. "I would like to be there, and just see Gusev becoming bigger and bigger in the last moments before landing," she said.
Aerial show
As Spirit dives through the Martian atmosphere, a complex set of actions must occur in rapid-fire order, such as: Unfurling a critical parachute, heatshield separation, radar scans of the approaching terrain, retro-rocket firings, and the inflation of a huge set of airbags to cushion the lander from repeat bounces before coming to full-stop on Mars.
To a person standing on the surface of Mars, that aerial show would be an eye-catcher for sure.
"I wish I could be sitting on Gusev floor and see Spirit landing, bouncing and finally come to rest on this place I have been thinking about so much in the past 13 years," Cabrol said. "With Gods help, in few days from now, we will see the first images of Gusev and I feel extremely privileged. For a planetary geologist, and for the time being, this is as close as one can get to being in the field on Mars."
First signal
As Spirit hurdles toward Gusev Crater, the spacecraft will initially communicate with Earth through a series of simple tones, letting controllers on Earth know the craft has completed various phases of its entry, descent, and landing.
The Deep Space Network (DSN) antennas on Earth could hear from Spirit Saturday night, but may not receive the first signal from a healthy spacecraft until Sunday evening.
Within the first 24 hours, Spirit will have several chances to communicate with Earth both directly to the DSN and through NASA's Mars Global Surveyor orbiter and NASA's Odyssey orbiter.
Both orbiters are now circling Mars, collecting science about the planet. They will each fly over Spirit's landing site within Gusev Crater, throughout the mission.
Growing planetary junkyard
Meanwhile, the enigmatic world appears to have claimed yet another robotic explorer. Mums the word from the British-built Beagle 2. It dropped onto Mars surface more than a week ago.
Repeated attempts to contact the lander have not been successful. Beagle 2 was targeted to land on Isidis Planitia, a large flat region that overlies the boundary between the ancient highlands and the northern plains.
While the British stiff-upper-lip is clearly in full bloom, the chances that the impressive science package is alive and well seem to be fading away, day by day.
If lost to Mars, the Beagle is one more piece of hardware heaped atop a growing planetary junkyard of earlier failed U.S. and Russian Mars missions that dot the planet.
"Death Planet"
"Mars has been a most daunting destination. Some, including myself, call it the Death Planet," noted Edward Weiler, associate administrator for NASAs space science programs during a recent press briefing. "Just getting to Mars is hardbut landing is even more so," he added.
NASAs Deep Space Network has contributed search time for the missing lander. But now the DSN is increasingly busier handling the links for both Spirit, as well as the NASA Stardust mission that is closing in on Comet Wild-2 for a January 2 flyby.
The next opportunity for retrieval of a signal from Beagle 2 will be with the European Space Agencys (ESA) Mars Express in the New Year. ESAs Mars Express is the orbiter that deployed the Beagle 2 and is now circling the planet.
ESA ground teams recently nudged the Mars Express from an equatorial orbit into a polar orbit around Mars.
That change of orbit will allow increasingly closer looks at the Beagle 2 landing site.
If Beagle 2 did successfully make it to the surface of the red planet intact, the reduced distance, the ideal angle of overflight and the pre-tested communications link between the 'mother' craft and its 'baby' Beagle 2 will increase the probability of catching signals from the lander.
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