Uh-oh. According to news sources in China, Yutu experienced a “mechanical control abnormality” shortly before lunar sunset on Friday as it entered round #2 of lunar hibernation. To protect their electronics during the approximately two-week long bitter cold winter night, most activities are shut down and rover and lander are kept warm with internal radioisotope heaters.
The abnormality occurred due to “the complicated lunar surface environment,” the State Administration of Science, Technology and Industry for National Defense was quoted.
Lutz Richter, a planetary rover specialist with Kayser-Threde, a German aerospace company that partners with NASA and the European Space Agency, speculates that there might be a problem with the motors that close the solar panels. The panels must be kept closed during the night to protect their internal electrical components from freeze damage.
Dust jamming up the works might also be the cause. Whatever happened, the rover didn’t respond correctly to commands and might very well be crippled for good. Temperatures at the landing site range from about 225 F (107 C) during the day to -292 F (-180 C) at night – a difference of over 500 degrees. That’s harsh.
You can read more about the trouble in Emily Lakdawalla’s excellent blog at the Planetary Society. There’s also a log or unofficial Twitter account set up where Yutu speaks in first person (like the Mars Curiosity Twitter site) about its day. Here’s a recent entry translated (roughly) from Chinese using Google Translate:
“The third good news is that yesterday morning, the lander has to sleep again, ready for the second coming of Moonlight. The bad news is, I had to sleep this morning should begin, but before going to sleep, my body found the master control abnormal, some parts of the body do not listen to their words. Now the masters are hard to find ways to feel not sleep, I heard more and more like their eyes rabbit …… Still, I know that there might not survive the Moonlight it. Before departure, I have had to learn together and lander human lunar history.”
Unfortunately, no further details have been provided except that scientists are trying their best to repair the problem. Given that the lander will be dormant for half a moon cycle, it will be some time before we learn if they’ll succeed.
During the first night-dormancy, the lander studied the Earth’s charged particle environment called the plasmasphere with an ultraviolet light sensitive camera and examined the sky with a small telescope. Except for a non-functioning color camera, the lander appears to be in good shape.
The Chang’e 3 mission to the moon is currently about halfway through its 90-day planned lifespan. I’ll update as more information becomes available.