Solar Powered Mars Rover Still Not Responding

NASA last heard from the solar powered Mars rover Spirit nine months ago and the team are now trying to revive it while solar energy resources on Mars are at their optimum.
    
The Spirit rover landed on Mars’ surface way back in January, 2004 on a mission that was only meant to last 3 months. Spirit and its twin Opportunity exceeded all expectations and Opportunity is continuing to function today, sending back valuable data to the NASA team on Earth.
   
Spirit’s demise has primarily been due to the loss of use of drive motors on two of its six wheels, which left it in an unfavourable position to harvest solar energy during the Martian winter, which began last May.
  
Spirit last communicated on March 22 last year, going into a low-power fault mode that would only allow for charging and heating its batteries and keeping its clock running. However, with most of the heaters not operating, the internal temperatures of the rover would have been subjected to incredibly cold conditions which may have caused further damage and perhaps prevent it from reawakening.
  
NASA’s Deep Space Network of antennas in California, Spain and Australia has been listening for Spirit each day and sending commands to try and get a response from the rover even if the Spirit has lost track of time – it may “forgotten” it is now Spring and it’s time to power up.
  
The Opportunity rover is still performing well and will spend its 7th birthday on the southwestern rim of a football-field-size crater called “Santa Maria.”
 
In May last year Opportunity rover beat the duration record set by NASA’s Viking 1 Lander of six years and 116 days operating on the surface of Mars. 
   
Both rovers are equipped with solar panels capable of generating around 140 watts of power for up to four hours each Martian day under ideal conditions. Energy storage for the rovers is in the form of two rechargeable lithium ion batteries weighing just over 7kg each.