The satellite has experienced major failures with aging components. One of four reaction wheels, one of three batteries, one of two star trackers, and two of two solar array drives have all been deemed unusable. While the solar array cannot rotate due to the failed drive, the solar array, itself, continues to charge the onboard batteries. Innovative changes to daily operations have allowed the mission to survive and continue to downlink scenes around the world
Further Information:
+ USGS Landsat website