Japan's lunar probe not generating power despite moon landing

Japan on Saturday became the fifth country to put a spacecraft on the moon, but solar power issues threatened to cut short the nation's mission to prove a "precision" landing technology and revitalize a space program that has suffered setbacks.

The Japan Aerospace Exploration Agency (JAXA) said its Smart Lander for Investigating Moon (SLIM) landed on the moon's surface at around 12:20 a.m. (1520 GMT Friday), but its solar panels were not able to generate electricity, possibly because they are angled wrong.

As SLIM's solar cells were not generating electricity, it was working on backup batteries which would only last for hours, JAXA officials told a press conference on Saturday. JAXA will maintain the status quo rather than take risky actions and hopes a shift in the sunlight's angle will hit the panels in a way that can restore its functions, Hitoshi Kuninaka, the head of JAXA's research center, told a press conference.

"It takes 30 days for the solar angle to change on the moon," Kuninaka said. "So when the solar direction changes, and the light shines from a different direction, the light could end up hitting the solar cell."

SLIM, a small probe about 2.4 meters high and weighing about 200 kg excluding fuel, is designed to test technology for conducting pinpoint landings on the surface of gravitational bodies with an unprecedented precision of less than 100 meters from intended targets, as opposed to conventional landers that often have an accuracy of within several kilometers, according to JAXA.

"Looking at the trace data, SLIM most certainly achieved a landing with 100-meter accuracy," Kuninaka said, adding it will take about a month to verify it.

The agency expects SLIM, dubbed the "moon sniper," to help unravel the moon's origins by carrying out a composition analysis of rocks believed to be part of its mantle. The 2.4m by 1.7m by 2.7m vehicle includes two main engines and 12 thrusters, surrounded by solar cells, antennas, radar and cameras. Keeping it lightweight was another objective of the project, as Japan aims to carry out more frequent missions in the future by reducing launch costs. SLIM weighed 700 kg at launch, less than half of India's Chandrayaan-3.

As the probe descended onto the surface, it was designed to recognize where it was flying by matching its camera's images with existing satellite photos of the moon. This "vision-based navigation" enables a precise touchdown, JAXA has said.

Shock absorbers make contact with the lunar surface in what JAXA calls new "two-step landing" method – the rear parts touch the ground first, then the entire body gently collapses forward and stabilizes.

On landing, SLIM successfully deployed two mini-probes – a hopping vehicle as big as a microwave oven and a baseball-sized wheeled rover – that would have taken pictures of the spacecraft and were slowly sending them back to Earth, JAXA said. Tech giant Sony Group, toymaker Tomy and several Japanese universities jointly developed the robots.

Due to the solar power system malfunctions, the agency said it was prioritizing data acquisition from the lunar surface, and proceedings with the obtained data would be updated in the future.

The rocket carrying SLIM was launched on September 7, 2023, from the Tanegashima Space Center in southwestern Japan, in the country's third attempt at a lunar landing.

In November 2022, JAXA lost contact with its Omotenashi lander and scrubbed an attempted landing. In April 2023, the Hakuto-R lander, built by Japanese startup ispace, successfully reached lunar orbit but crashed during its touchdown attempt.

(With input from agencies)