The European Philae lander sitting on the surface of a distant comet has sent scientific data on the space rock back to Earth, but it may be the last because its failing batteries have put the lander in a standby mode, controllers say.
The European Space Agency lander, after being released by the Rosetta spacecraft, bounced off Comet 67P/Churyumov-Gerasimenko in its first landing attempt and then settled on the surface against a cliff in deep shadow that's not allowing sunlight to reach its solar energy panels.
Still, ESA scientists say, it managed to transmit what they've called a treasure-trove of research data before it went silent.
"Philae has fallen into 'idle mode' -- a possibly long silence," they posted on an ESA blog. "In this mode, all instruments and most systems on board are shut down."
Before mission controllers put the lander to sleep it managed to successfully drill into the comet for samples and send back analysis data from a majority of its 10 onboard instruments, they said.
"Prior to falling silent, the lander was able to transmit all science data gathered during the First Science Sequence," project manager Stephan Ulamec said. "This machine performed magnificently under tough conditions, and we can be fully proud of the incredible scientific success Philae has delivered."
Drilling into the comet's surface and obtaining samples for analysis was considered the core mission Philae was designed for.
The comet rotates in a 12-hour "day," but because of the lander's position hard up against a cliff it is only receiving about 1.5 hours of direct sunlight in that time, not enough to keep its battery charged.
However, there is a possibility that could change, says Mark McCaughrean, a senior scientific adviser to the ESA.
"Philae could come back later as we move closer to the sun, and we get more light onto the solar panels up against the cliff we're at here in the shadows," he says.
During the approach to the sun there will be changes to the timing, intensity and angle of the sunlight shining on the solar panels, ESA scientists say.
The comet will make its closest approach to the Sun on Aug. 13, 2015, swinging by at a distance of around 115 million miles between the orbits of Earth and Mars.
Philae's troubles began when two harpoons meant to anchor the lander to the comet failed to deploy and it bounced almost 0.6 miles way from the surface.
In a subsequent attempt to land, the dishwasher-sized Philae bounced another two times before coming to rest a half mile from its intended landing site.