Spirit Registers Success in Backward Drive

Engineers at NASA announce that they are beginning a new stage of the attempts to extricate Spirit from Troy. According to the team, the exploration robot will start driving backwards again, as this appears to be the only remaining way of getting it out of the patch of loose Martian soil that has been keeping it prisoner since last May. Mission managers, based at the NASA Jet Propulsion Laboratory (JPL), in Pasadena, California, have attempted a number of extrication options thus far, but results have been modest at most, and the Red Planet is about to enter the winter season again.

The first two drive attempts in the new configuration produced some good news, after weeks of failures. The rover team reports about 6.5 centimeters (2.6 inches) of horizontal motion, and also a slight lift, which could mean that the battered Spirit is finally beginning to emerge from its trap. “Spirit performed the first backwards drive (toward the south) on Sol 2045 (January 14). Until then, all drives since extrication attempts begun two months earlier had been with forward driving, with Spirit facing northward. Backward driving includes the additional technique of steering the wheels side-to-side before performing each step,” JPL experts write on their website.

“The hypothesis for the wheel steering is two-fold. The process clears out material in front of the wheel and allows material to slough off the face of the wheel trench and provide traction under the wheel. Also, the flat surface of the wheel's side 'kicks' against loose material, like a swimmer's frog kick or breast stroke, to provide some push,” they add. The wheels spun for sufficient time on January 14 to result in about 30 meters (98 feet) of movement under normal conditions. The drive was done in six, 5-meter steps, and the rover recorded 3 centimeters (1.2 inches) of backwards motion and 1 centimeter of lift .

The second drive took place on Sol 2047 (January 16), when the explorations robot, which recently turned 6, moved about 3.5 centimeters (1.4 inches) backward, and also climbed about 0.3 centimeters (0.1 inch). Still, experts warn against popping out the champagne just yet. “Spirit is still down about 3 centimeters (1.2 inches) in altitude since extrication started. It is important to remember that the right-rear wheel is still non-functional, along with the right-front wheel,” they say.

Spirit was heading for a feature known as Home Plate, on a 12-degree slope, when it drove into Troy. The main concern now is getting a chance to position the rover in the most favorable configuration before winter starts, so that it gets the maximum amount of solar energy possible. The machine has already endured several winters on the Red Planet, despite the fact that it was originally programmed to only last for about 3 months.