The lander was photographed upside down on the lunar surface. Credit: JAXA/TOMY Company/Sony Group Corporation/Doshisha
Defying expectations, Japan’s spacecraft, which touched down with unprecedented precision near the Moon’s equator last month, has survived the harsh lunar night and started communicating with Earth again. On Sunday, a command was sent to the Smart Lander for Investigating Moon, or SLIM, and a response was received, according to the Japanese Space Agency (JAXA).
SLIM was not designed to survive the deep cold night on the lunar surface, where temperatures drop below minus 130 degrees Celsius. JAXA’s engineers had remained hopeful that it would make it through the night, says SLIM project manager Shinichiro Sakai, but its message home was “a nice surprise”. “We knew that some of NASA’s Surveyors survived, so we felt we should also have some chance,” he says.
He believes the lander’s communications system, onboard computer and solar panels are working. JAXA announced later on social media that it was attempting to take new images with a multiband spectroscopic camera used to study the composition of rocks.
It’s been a rollercoaster ride for SLIM. Despite a successful on-target landing, JAXA lost contact with SLIM for some days when it rolled upside down. With its solar panels oriented the wrong way, it had only a trickle of energy with which to snap a photo and send it home before lunar night fell. The next lunar sunset for SLIM will take place on Thursday.
During the lunar day, extreme heat also becomes a problem for SLIM. With the Sun high, its radio electronics overheat very quickly and Sakai says the team will need to wait for the temperature to cool later in the week before they restart scientific investigation.
Electronic circuit boards can fail when they get too warm or cold, because they are built with different materials and the materials have different contraction rates, says Simeon Barber, a planetary scientist from Open University in Milton Keynes, UK. “It can generate significant twisting and stretching forces, and cause components or joints to crack or be pulled apart,” he says.
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Both SLIM and the US spacecraft Odysseus, which made history last week by becoming the first privately built Moon-lander to complete a soft touchdown, experienced issues with landing positions. “Landing on the Moon is as difficult as it has always been,” says Barber.
The two recent spacecraft were built within many constraints, in particular cost, which places limits on their size and technology. “The two landers got almost everything right, but went awry at the last moments,” he says.
However the teams have obtained lots of data that will inform future attempts. “The best way to land successfully is to keep trying and to learn from previous attempts,” says Barber.