Japan's Moon Lander SLIM's Solar Panels Fail To Generate Electricity After Touchdown

SLIM ('Smart Lander for Investigating Moon'), has touched down on the moon's surface. The  spacecraft which reached lunar orbit on Christmas Day(Dec. 25),  performed a crucial engine burn on Jan. 14, circularizing its orbit at the 600-kilometer altitude and setting the stage for descent-and-landing operations. Another burn earlier on Jan 19, which took SLIM's orbit down to about 15 km above the lunar surface, culminated in the landing try, which began at about 1500 UTC; and reportedly lasted up to 20 minutes. Not clear yet if it achieved its target point of landing 100 meters within the Shioli Crater.

Japanese Aerospace Exploration Agency, JAXA, on Sept. 6, launched a H-2A rocket carrying the SLIM and XRISM('X-Ray Imaging and Spectroscopy Mission') space telescope, from Tanegashima Space Center at 2342 UTC. Both spacecraft were deployed on schedule, sequentially less than an hour after liftoff.

At liftoff, SLIM which measures 2.4 m high, 2.7 m long and 1.7 m wide, weighed about 700 kilograms, but roughly 70% of that weight was propellant.

Both spacecraft deployed into Earth orbit, where XRISM remains. But SLIM left our planet's gravity well on Sept. 30, and began its journey on the long, circuitous and energy-efficient route to the moon.

The moon lander carries two miniprobes. LEV-1 ("Lunar Excursion Vehicle" 1) and LEV-2 deployed as planned after touchdown, and LEV-1 was known to be operating on the lunar surface. According to JAXA, those two little craft will help the mission team monitor the status of the larger lander, take photos of the landing site and provide an "Independent communication system for direct communication with Earth."

SLIM "aims to achieve a lightweight probe system on a small scale and use the pinpoint landing technology necessary for future lunar probes," JAXA officials wrote in a mission description. "The project will aim to cut weight for higher-function observational equipment and to land on resource-scarce planets, with an eye towards future solar system research probes."

During descent on Jan. 19, SLIM hit its various milestones, and the lander communicated with its handlers all the way through, and beyond, its historic touchdown.

However, JAXA couldn't immediately confirm SLIM's status after landing. About an hour later, the agency gave an update via a press conference, explaining the spacecraft's power problems.

SLIM's solar panels failed to generate electricity on the surface of the moon, leaving the lander's future in serious doubt.

It's unclear why the solar cells aren't working, officials said. But it's unlikely they were damaged during the touchdown, because SLIM's other hardware appears to be fine and functional. It's possible that the lander isn't oriented toward the sun as expected, according to JAXA.

Early Monday morning (Jan. 21), JAXA said the lander has not been declared dead, and its handlers are working toward a possible recovery. 

When SLIM's battery power dipped to 12% capacity on the lunar surface, the lander powered down intentionally "to avoid being unable to restart for a recovery operation due to over-discharge," team members explained early Monday via the mission's account on X.

"According to the telemetry data, SLIM's solar cells are facing west," the team said in a separate X post on Monday. "So if sunlight begins to shine on the lunar surface from the west, there is a possibility of generating power, and we are preparing for recovery. #SLIM can operate with power only from the solar cells."

SLIM successfully beamed home technical data and imagery collected during Friday's descent and landing, the team added in another Monday X post.

Meanwhile on our Earth orbit, XRISM which is a collaboration involving JAXA, NASA and the European Space Agency (ESA) will study the universe in high-energy X-ray light.

"X-ray astronomy enables us to study the most energetic phenomena in the universe," Matteo Guainazzi, ESA project scientist for XRISM, said in a statement. "It holds the key to answering important questions in modern astrophysics: how the largest structures in the universe evolve, how the matter we are ultimately composed of was distributed through the cosmos, and how galaxies are shaped by massive black holes at their centers."

The observatory will focus particularly on the super-hot gas surrounding galaxy clusters. 

"JAXA has designed XRISM to detect X-ray light from this gas to help astronomers measure the total mass of these systems," ESA officials wrote in the statement. "This will reveal information about the formation and evolution of the universe."

Also studying the heavens from Earth orbit, are NASA's Chandra X-Ray Observatory and ESA's XMM-Newton, both of which launched in 1999, as well as NASA's NuSTAR, which lifted off in 2012.

WATCH the launch, landing and news conference about SLIM