It appears the end is nigh for the Phoenix Mars Lander. Today, engineers have begun to shut down some of the lander’s instruments and heaters. But this is in hopes of extending the mission by saving power as available sunlight begins to wane with the approach of Martian autumn. But at the same time, the spacecraft requires more power to run heaters in order to survive as the temperatures decline. “If we did nothing, it wouldn’t be long before the power needed to operate the spacecraft would exceed the amount of power it generates on a daily basis,” said Phoenix Project Manager Barry Goldstein of NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “By turning off some heaters and instruments, we can extend the life of the lander by several weeks and still conduct some science.”
Today, commands were sent to disable the first heater, one that warms the robotic arm, the robotic arm camera and the TEGA instrument – the Thermal and Evolved Gas Analyzer. Likely, this means no more digging and no more “baking and sniffing” of soil samples. Engineers say by shutting down this heater, they’ll save 250 watt-hours of power.
Over the next several weeks, four survival heaters will be shut down, one at a time, in an effort to conserve power. The heaters serve the purpose of keeping the electronics within tested survivable limits. As each heater is disabled, some of the instruments are also expected to cease operations. The energy saved is intended to power the lander’s main camera and meteorological instruments until the very end of the mission.
Engineers are also preparing for solar conjunction, when the sun is directly between Earth and Mars. Between Nov. 28 and Dec. 13, Mars and the sun will be within two degrees of each other as seen from Earth, blocking radio transmission between the spacecraft and Earth. During that time, no commands will be sent to Phoenix, but daily downlinks from Phoenix will continue through NASA’s Odyssey and Mars Reconnaissance orbiters. At this time, controllers can’t predict whether the fourth heater would be disabled before or after conjunction.
In the final step, Phoenix engineers may turn off a fourth heater — one of two survival heaters that warm the spacecraft and its batteries. This would leave one remaining survival heater to run out on its own.
“At that point, Phoenix will be at the mercy of Mars,” said Chris Lewicki of JPL, lead mission manger.
The Phoenix team has parked the robotic arm on a representative patch of Martian soil. No additional soil samples will be gathered. The thermal and electrical-conductivity probe (TECP), located on the wrist of the arm, has been inserted into the soil and will continue to measure soil temperature and conductivity, along with atmospheric humidity near the surface. The probe does not need a heater to operate and should continue to send back data for weeks.
Throughout the mission, the lander’s robotic arm successfully dug and scraped Martian soil and delivered it to the onboard laboratories. “We turn off this workhorse with the knowledge that it has far exceeded expectations and conducted every operation asked of it,” said Ray Arvidson, the robotic arm’s co-investigator, and a professor at Washington University, St. Louis.