Ispace’s Japanese lunar lander crashed due to a software bug

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A review of the data revealed that the software controlling the descent appeared to have lost track of the lander’s altitude as it flew over the rim of a crater on the lunar surface that was about two miles higher than the surrounding terrain.

The software incorrectly concluded that the sensor had malfunctioned and in fact discarded correct altitude readings.

The engine, altimeter, and other hardware functioned properly, indicating that the spacecraft’s overall construction is sound. Software fixes are easier to implement than major hardware overhauls.

“This is not a hardware failure,” Ryo Ujiie, Ispace’s chief technology officer, said during a news conference on Friday. “We don’t have to modify the hardware side.”

However, the failure pointed to flaws in Ispace’s testing of the spacecraft’s landing software, developed by the Draper Laboratory in Cambridge, Massachusetts.

A decision to change the landing site after the spacecraft’s design was finalized in early 2021 most likely contributed to the crash.

Originally, those responsible for Ispace had chosen Lacus Somniorum, a flat area, as the landing site. But then they decided that Atlas, an impact crater more than 50 miles wide, would be a more interesting target.

That meant the landing software wasn’t designed to handle the change in altitude as the spacecraft flew over the crater rim, and simulations couldn’t detect this oversight.

On Tuesday, NASA released images from its Lunar Reconnaissance Orbiter that appeared to show the crash site.

Background: A bumpy road to the moon.

A mix of private companies, organizations, and government space agencies have attempted to return to the moon in recent years. But landing on the lunar surface turned out to be more difficult than many had expected.

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The Beresheet lander, owned by an Israeli non-profit organization called SpaceIL, launched to the moon in 2019 but crashed. The Indian Space Research Organization also attempted to land a lunar spacecraft in the same year and that craft, Vikram, also crashed.

Only China has recently landed robotic spacecraft on the moon, with three successes in three attempts over the past decade.

What’s next: Try again.

Takeshi Hakamada, Ispace’s founder and chief executive officer, said the timeline for the company’s next two missions — with a nearly identical lander next year and a larger spacecraft on the far side of the moon in 2025 — remains largely unchanged.

“We have a very clear picture of how to improve our future missions,” said Mr. Hakamada.

Ispace has taken out insurance for the lander and the financial impact on the company is small, Mr. Hakamada said.

More spaceships are due to launch to the moon later this year. Pittsburgh-based Astrobotic Technology and Houston-based Intuitive Machines plan to send spacecraft to the moon later this year as part of a NASA program that hires private companies to bring scientific instruments to the moon.

The Indian Space Agency also announced this week that Chandrayaan-3, a follow-up to its 2019 lunar landing attempt, could launch as early as July 12.