The Phoenix Mars Lander team started turning off heaters and instruments today to conserve power and extend the life of the probe by several weeks and perhaps continue to still do some science. [right, under the lander. Credit, NASA-JPL/CalTech, UA, Max Planck Inst.]
Four survival heaters will be shut down, one at a time, that keep the electronics within tested survivable limits. Certain instruments will stop operating as each heater is shut down. The remaining energy is intended to power the lander’s main camera and meteorological instruments until the very end of the mission.
The first heater to be turned off today "warms Phoenix’s robotic arm, robotic-arm camera, and thermal and evolved-gas analyzer (TEGA), an instrument that bakes and sniffs Martian soil to assess volatile ingredients. Shutting down this heater is expected to save 250 watt-hours of power per Martian day."
A second heater powers a unit that hasn’t been used since landing, while "the third heater warms Phoenix’s main camera -- the Surface Stereo Imager –and the meteorological suite of instruments. Electronics that operate the meteorological instruments should generate enough heat on their own to keep most of those instruments and the camera functioning."
Once they turn off the fourth heater -- one of two survival heaters that warm the spacecraft and its batteries -- the last remaining survival heater will run out on its own.