PASADENA, Calif. -- Teams of engineers are reconstructing the entry, descent, and landing of Spirit on Mars, piecing together how well the spacecraft behaved as it plummeted through the martian atmosphere onto the surface of the red planet.
Early assessments suggest that Spirit plowed through strong gusts of winds, so much so, that special onboard gear was triggered to assure the spacecraft safely survived the ordeal.
Despite the harrowing plunge through turbulent air, Spirits airbag touchdown was less severe than that experienced by the Mars Pathfinder/Sojourner rover in 1997. That mission also made use of an airbag landing system.
Secure in its cocoon of airbags, Spirits first impact shot it up into the air some 26 feet (8 meters), followed by some two dozen bounces and skips before coming to rest on the martian surface.
Lessons learned
Here at the Jet Propulsion Laboratory (JPL), a major reconstruction effort is underway to stitch together engineering data about Spirits successful touchdown.
Lessons learned are being filtered into decisions regarding the upcoming landing attempt by Spirits twin craft, Opportunity.
Opportunity is now speeding toward Mars, headed for a January 24 touchdown at roughly 9:05 p.m. Pacific Standard Time.
"We are going to do a full-up reconstruction," said Pete Theisinger, Project Manager for the Mars Exploration Rover (MER) project. A team of engineers, as well as independent reviewers are part of the effort.
End-to-end test for real
Putting aside years of testing pre-launch, the only real "end-to-end" appraisal of the technology came during Spirits actual entry, descent, and landing on Mars.
"We will be basically comparing our expectations for what we thought might happenand all these observables to what really happened," Theisinger told SPACE.com .
Now being assessed are computer software changes that alter parachute deployment time and other parameters to maximize Opportunitys chances of success. But there is also trepidation of altering too many things that could snowball into a bad day.
On the DIMES
The Mars Exploration Rover (MER) design has new tools, absent on the Mars Pathfinder/Sojourner that landed on the red planet in 1997.
Adding this equipment was hotly debated in engineering circles as to its need. The hardware was specially designed to avoid excessive horizontal speed caused by strong winds as the spacecraft raced toward ground impact.
Innovations carried by Spirit and Opportunity include a set of three small transverse rockets mounted on the spacecrafts backshell that can be fired in any combination. Doing so reduces horizontal velocity or counteracts effects of side-to-side swinging of the landing system as it nears Mars surface.
Also carried for the first time was the Descent Imager Motion Estimation System (DIMES) - a downward-looking camera mounted on the lander. Once onboard radar senses the surface, this camera dutifully takes three pictures of the ground about four seconds apart. It then rapidly analyzes them to estimate the spacecraft's horizontal velocity.
Unexplained occurrences
Looks at Spirit data has confirmed that DIMES worked like a champ, triggering rockets to dampen wind effects that were unexpectedly strong. A point of discussion is whether or not Spirit survived thanks to use of the DIMES/rocket activation or despite the system.
"There is an entire story just on the reconstruction alonea lot of fascinating stuff," said Gentry Lee, Chief Engineer for the Mars program at JPL.
Meetings about the entry, descent, and landing data are held every day for hours, with engineers and managers arguing about what the data means.
"There are some unexplained occurrences. Were trying to extract the information and see how it applies to Opportunity," Lee told SPACE.com .
"We have loads of quality data. This is a job of analyzing and synthesizing an enormous amount of data in a very short period of time," Lee said.
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