Japan's 'Moon sniper' and its two ejectable landers make it into space

Japan's space exploration agency (JAXA) has successfully launched a rocket carrying the Smart Lander for Investigating Moon (SLIM) – an effort to test new technologies that allow spacecraft to pick their own landing locations.

SLIM ascended atop a H-IIA launch vehicle that soared skyward at 08:42 Thursday local time (2342 Wednesday UTC). It separated from the launcher on schedule.

The H-IIA is a Mitsubishi Heavy Industries product, largely used for commercial satellite launches. Thursday's launch was the 47th mission for the rocket, which has recorded only one failure – and that was in 2003.

JAXA plans just three more H-IIA launches, although its intended replacement – the H3 – failed on its first mission. The space agency's previous launch also failed when the Epsilon rocket veered off course in October 2022 and consigned eight commercial satellites to a fiery end.

Anticipation for the launch of SLIM was therefore high, because it had been delayed for a few days on account of adverse weather. Those delays came after its planned 2021 launch date was pushed back because of problems with another mission that rode the same rocket. More on that later.

SLIM's main objective is to test precision landing tech.

Most spacecraft land where they're told and have limited ability to survey the terrain beneath them and select a safe spot to touch down.

SLIM carries high-resolution cameras, and its onboard computers have models of the Moon's surface. Those computers also run algorithms that allow it to compare input from the cameras with the models, then select its own landing location.

If that succeeds, the hope is that SLIM's tech will be useful for future sample return missions. And also just to improve the chances of success for any mission that touches down on non-terrestrial bodies.

The precision landing tech helps to reduce SLIM's weight, making the mission of importance as a test for smaller craft that nonetheless take on weighty tasks.

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SLIM also carries a pair of probes that will be ejected from the lander. One weighs just 250g and transforms from spherical shape to a cylinder. That rolling rover – the Palm-Sized Lunar Excursion Vehicle 2 – will be ejected as SLIM enters free fall to the lunar surface. During its short life it will take photos of the Moon, and SLIM, and attempt to roll around.

Those snaps will be sent to Lunar Excursion Vehicle 1 (LEV-1), which has the ability to hop very short distances. LEV-1 can establish direct contact with Earth.

Back to that other mission that rode the H-IIA. It's called XRISM – the X-Ray Imaging and Spectroscopy Mission – and will occupy a low Earth orbit from which it will observe gas in galaxy clusters, the chemical enrichment of the Universe, and extreme physics around accreting supermassive black holes.

SLIM will take at least four months to reach Luna, then spend another month in orbit before attempting its descent.

XRISM will, as is usually the case with space 'scopes, be calibrated and tested for a few months before formal observations commence. ®