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Japan just became the fifth country to successfully land on the moon!

....at least, we think

Japan has reached the moon!! Whether the landing was considered successful is a little more unclear, but it LOOKS to be a success. Here’s what happened.

This morning, on January 19 around 10:20 am ET, I THINK Japan successfully soft landed an uncrewed spacecraft on the moon. The spacecraft, SLIM, or Smart Lander for Investigating the Moon, is intact, it’s currently receiving and responding to signals, and the two rovers LEV1 and LEV2 have successfully deployed. BUT. Unfortunately, the lander’s solar cells aren’t generating power, so the spacecraft is currently running on battery power.

Despite the solar cells, I do think this IS a successful landing. It’s not clear exactly what the problem with the solar panels is, though there’s speculation that the lander rolled after landing. (There was some concern that the lander toppled over — that was actually supposed to happen according to the mission briefing.)

Credit: JAXA

But it may have changed position or rolled after falling over, which could be the challenge with the solar panels — basically they’re at the wrong angle to gather sunlight and generate power. JAXA has made clear they are prioritizing data retrieval and downloading images over troubleshooting the solar cells, as they have several hours of battery life. They will continue trying the solar cells in two weeks as the sun changes angles thanks to the moon’s rotation (which makes the issue sound like a solar panel orientation and direction issue, but the flip side is the craft has to survive the extremely cold lunar nights) — JAXA did make clear that they don’t think the spacecraft damaged the solar panel on landing or fell on the solar panels and damaged them. It’s not a hardware issue.

Credit: JAXA

JAXA did release the minimum success criteria before the mission launched, which is soft landing of the SLIM spacecraft by using vision-based landing. They achieved that. Officials at the organization do also think they achieved the precision landing within 100 m of their target, but it will take a month or so to confirm. Being able to do things on the moon after landing is extra, and they’re even going to be able to do that.

Credit: JAXA

SLIM didn’t burn up in Earth’s atmosphere (sorry Peregrine), it didn’t slam into the moon, but it doesn’t have working solar panels. Is this a success? JAXA is making clear that they think it is. The reason it matters because if the SLIM landing is considered a success, that would make Japan the fifth country to successfully land on the moon, after the US, former Soviet Union, China, and India.

I personally consider this a success. Being able to land a craft on the moon with that kind of precision is very cool, and the systems worked during descent. Engines fired when they were supposed to, the spacecraft didn’t crash into the moon’s surface. We’re receiving telemetry from the spacecraft, and the rovers are exploring the surface (and they have independent communication capability so even if JAXA is unable to generate power, they will continue to explore and send back data.) They’re going to continue working the problem and we should get more information in the next few days and weeks.

It’s not my decision, but I’m calling this one a win.