The end may be near for Philae after scientists from the European Space Agency (ESA) have stopped contact attempts with the comet lander. After bouncing around on the surface of Comet 67P/Churyumov–Gerasimenko, Philae landed in a location that received limited sunlight. With the comet on its return voyage to deep space, the temperature may be too cold for Philae to wake up.
In a last ditch effort to establish contact with Philae, the lander team tried to turn on Philae's momentum wheel switch in January. If the momentum wheel could be activated, the team could potentially reposition Philae to receive more sunlight. The window was closing because temepratures would reach -51 degrees Celsisus (-59 degrees Fahrenheit) when comet 67p would be 300 million kilometers (186.4 million miles) from the sun.
"The chances for Philae to contact our team at our lander control center are unfortunately getting close to zero,” Stephan Ulamec, Philae project manager at the German Aerospace Center, said in a statement. “We are not sending commands anymore, and it would be very surprising if we were to receive a signal again."
The Philae lander was part of the larger Rosetta mission that launched in 2004. After a gravitational assist from Mars and two asteroid flybys, Rosetta entered deep space hibernation in 2011. After close to three years sleeping, the spacecraft was turned on in January 2014 ahead of a summer rendezvous with its comet target. After successfully orbiting comet 67P in August, the next phase of the mission was to place a lander on the comet in November 2014.
Everything was working according to plan until one of Philae's thrusters failed. That glitch was followed by the lander's harpoons failing to deploy. Philae was unable to attach itself to the landing site, which led it to bounce around the comet before landing in a site known as Abydos. The final resting spot of Philae is still unknown.
The comet lander remained silent for the remainder of the year, with the team hoping Philae would wake up when the comet reached its closest point to the sun in August 2015. The lander made contact Rosetta eight separate times between June 13 and July 9. Despite the bumpy landing, Philae was able to complete 80 percent of its science mission.
Rosetta will orbit comet 67P until it makes a controlled impact on the surface of the comet in September. Before the descent, Rosetta will pass over Abydos in a final attempt to determine Philae's resting place. "Determining Philae’s location would also allow us to better understand the context of the incredible in situ measurements already collected, enabling us to extract even more valuable science from the data," Matt Taylor, ESA’s Rosetta project scientist, said in a statement.