The rover team anticipated Spirit would go into a low-power “hibernation” mode since the rover was not able to get to a favorable slope for its fourth Martian winter, which runs from May through November. The low angle of sunlight during these months limits the power generated from the rover’s solar panels. During hibernation, the rover suspends communications and other activities so available energy can be used to recharge and heat batteries, and to keep the mission clock running.
On July 26, mission managers began using a paging technique called “sweep and beep” in an effort to communicate with Spirit.
“Instead of just listening, we send commands to the rover to respond back to us with a communications beep,” said John Callas, project manager for Spirit and its twin, Opportunity, at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “If the rover is awake and hears us, she will send us that beep.”
Based on models of Mars’ weather and its effect on available power, mission managers believe that if Spirit responds, it most likely will be in the next few months. However, there is a very distinct possibility Spirit may never respond.
“It will be the miracle from Mars if our beloved rover phones home,” said Doug McCuistion, director of NASA’s Mars Exploration Program in Washington. “It’s never faced this type of severe condition before – this is unknown territory.”