Japanese Moon Lander Crashed Because of a Software Glitch

A review of data showed that the software guiding the descent appeared to lose track of the landers’s altitude when it passed over the rim of a crater on the moon’s surface that was about two miles higher than the surrounding terrain.

The software erroneously concluded that the sensor had malfunctioned and rejected altitude measurements that were actually correct.

The engine, altimeter and other hardware operated properly, indicating that the overall design of the spacecraft is sound. Software fixes are easier to complete than major hardware overhauls.

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

The failure, however, pointed to shortcomings in Ispace’s testing of the spacecraft’s landing software, which was developed by Draper Laboratory of Cambridge, Mass.

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

Originally, Ispace officials had chosen Lacus Somniorum, a flat plain, as the landing site. But then they decided that Atlas, an impact crater more than 50 miles wide, would be a more interesting destination.

That meant the landing software was not designed to handle the change in altitude as the spacecraft passed over the crater rim, and simulations did not catch that oversight.

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

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

The Beresheet lander, from an Israeli nonprofit named SpaceIL, launched to the moon in 2019, but it crashed. The Indian Space Research Organization attempted to land a lunar spacecraft the same year, too, and that vehicle, Vikram, also crashed.

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

Takeshi Hakamada, the founder and chief executive of Ispace, said the schedule for the company’s next two missions — involving an almost identical lander next year and a larger spacecraft in 2025 to the far side of the moon — remains largely unchanged.

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

Ispace had obtained insurance for the lander, and the financial impacts on the company would be small, Mr. Hakamada said.

More spacecraft are scheduled to launch to the moon later this year. As part of a NASA program that is hiring private companies to take scientific instruments to the moon, Astrobotic Technology of Pittsburgh and Intuitive Machines of Houston, are scheduled to send spacecraft to the moon later this year.

The Indian space agency also announced this week that Chandrayaan-3, a follow-up to its moon landing attempt in 2019, could launch as early as July 12.

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