Japan’s space agency, JAXA, achieved a historic soft landing with SLIM on Friday morning, but the lander ran into instant trouble by not being able to collect solar energy and generate electricity. Hopeful for some westerly sunshine, JAXA is cautiously optimistic that SLIM could spring back to life in a couple of weeks.
Shortly after its landing on Friday January 19, JAXA reported issues with SLIM’s solar cells, which were not generating sufficient electricity. On Monday, JAXA revealed that it had shut down the system approximately three hours after landing to conserve its remaining power, as the space agency noted on X. The decision was made when SLIM’s battery level fell to 12 per cent, as this low battery level threatened to cause issues for future recovery if mission controllers didn’t disconnect it in time.
Despite the setback, this marks a historic achievement for Japan’s space exploration efforts. The successful soft landing on the Moon places Japan as the fifth nation to achieve this complex feat, joining the ranks of the United States, Soviet Union, China, and India. The lander, also known as the “Moon Sniper,” aimed for a precision landing within a 328-foot (100-meter) target area inside Shioli Crater, a 984-foot-wide (300-meter) impact basin.
Further analysis revealed that SLIM’s solar cells are facing west, away from the Sun. This orientation poses a challenge for power generation, especially since Moon missions typically land at the start of the lunar day when the Sun rises in the east, providing about two weeks’ worth of continuous sunlight. As it is currently lunar morning at SLIM’s location in Shioli Crater, the lander may need to wait until the lunar afternoon for its solar cells to catch enough sunlight to recharge its batteries. “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,” JAXA explained on X, adding that SLIM “can operate with power only from the solar cells.”
Despite these challenges, there is some positive news from JAXA. The agency reported that technical and image data acquired during SLIM’s descent and active time on the lunar surface were successfully transmitted back to Earth before power was switched off. JAXA plans to release more details by the end of the week, including word on whether SLIM managed to land within its constrained target area. We’re looking forward to seeing the photos taken from the surface as well.
In addition to its primary mission (the precision landing), SLIM carried two smaller rovers, which preliminary data suggests were ejected as planned before the lander touched down. It also housed various scientific instruments, including an infrared camera, thermometer, and radiation detector. The success of these elements of the mission remains to be fully assessed.
This milestone for JAXA comes in the wake of a recent setback in lunar exploration when Astrobotic’s Peregrine lander failed shortly after reaching space due to a propellant leak. Landing on the Moon remains an incredibly challenging endeavour, even with 21st-century technology.
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