The Phoenix lander's 90-day mission at the Mars pole is to gather dirt and rock samples with its robotic arm, analyze the samples with onboard instruments, and communicate results and respond to commands with its earthbound project engineers. All of these tasks require electrical power. The power-generation, -regulation, and -delivery system for the Phoenix comprises a lithium-ion-battery pack from Yardney Technical Products and two solar arrays from ATK Space Systems.

The oncoming Martian winter constrains the mission to a tight, 90-day window. Temperatures then drop to the point at which the atmosphere, which is more than 95% carbon dioxide, freezes solid and shrouds the lander in dry ice. The Phoenix will then shut down for the winter—and, most likely, forever.