Japanese aerospace company ispace has announced that its second lunar lander mission, Resilience, likely ended in a crash due to problems with the laser rangefinder, a critical device used to determine altitude during descent.
At a press briefing on June 23, ispace executives explained that an investigation into the missed landing on June 5 revealed a hardware problem that hindered the rangefinder’s ability to deliver timely altitude data.
The laser rangefinder was intended to provide readings from at least three kilometers above the lunar surface and trigger the engines for a final landing burn.
However, it only registered its first altitude measurement when the lander was less than 900 meters above the surface.
As a result, the lander attempted a rapid deceleration but was traveling significantly faster than planned, at 66 meters per second compared to the intended 44 meters per second.
Telemetry data showed that the last reported descent, at an altitude of 192 meters, demonstrated the lander was still descending at a speed of 42 meters per second.
Images released by NASA’s Lunar Reconnaissance Orbiter on June 20 confirmed the likely crash site, located approximately 282 meters south and 236 meters east of the planned landing zone, where the lander created a crater measuring 16 meters in diameter.
Yoshitsugu Hitachi, executive vice president of the Japan Engineering Office at ispace, stated during the briefing that the company first assessed whether the issue stemmed from hardware or software malfunctions.
Analysis of telemetry data ruled out any software problems and confirmed the propulsion system was functioning correctly.
Consequently, ispace shifted its focus to the laser rangefinder, finding no evidence of improper installation.
This led the team to believe that the rangefinder’s performance had degraded in some manner compared to pre-flight tests conducted prior to the mission’s launch.
Possible factors contributing to this degradation could include lunar surface conditions limiting laser light reflection, reduced power of the laser, changes in performance at higher velocities, or environmental effects such as vacuum or radiation exposure.
Hitachi emphasized the challenges in pinpointing the exact causes of the anomaly and whether it resulted from a single factor or a combination of issues.
He clarified that the cause of Resilience’s failure was distinct from the company’s first mission in 2023, where a software glitch fooled the lander into thinking it was closer to the surface than it was, leading to a crash after fuel exhaustion.
In contrast, the software on Resilience fully functioned as designed.
While the first lander experienced no issues with its laser rangefinder, Resilience had to employ a different model, as the supplier of the previous version had stopped manufacturing it.
To address the issues highlighted by the mission’s failure, Ryo Ujiie, ispace’s chief technology officer, outlined two principal steps the company plans to undertake.
The first step is to enhance the testing procedures for the laser rangefinder and related sensors to better simulate the conditions expected during the mission, characterized by high descent speeds and low lunar surface reflectivity.
The second action involves the consideration of an alternative laser rangefinder, as the one used in Resilience had not previously been flight-tested.
Ispace is also contemplating augmenting the laser rangefinder with additional sensor technologies, such as lidar or cameras, to facilitate terrain relative navigation.
These strategic changes will be supported by a new external review board that will include former engineers from NASA and the Japan Aerospace Exploration Agency (JAXA).
Moving forward, ispace intends to collaborate more closely with JAXA to leverage its technical expertise for upcoming missions.
These adjustments will not alter the timeline for the next two missions: Mission 3, which includes a lander developed by ispace U.S. for Draper and a NASA mission, and Mission 4, consisting of a Japanese-built lander.
Both missions remain on schedule for launch in 2027.
Ispace anticipates incurring approximately 1.5 billion yen (around $10.3 million) in additional costs associated with acquiring an improved laser rangefinder and enhancing testing protocols.
Takeshi Hakamada, CEO of ispace, expressed the company’s seriousness regarding the failures associated with its past missions.
However, he emphasized the importance of perseverance in the face of setbacks, stating, “There can be some failures, but we keep improving our systems.”
Hakamada reaffirmed ispace’s commitment to moving forward into future missions confidently, promising to regain the trust of customers and stakeholders.
He noted, “Our primary goal today was to convey that ispace, as a challenger, is already moving forward towards its next mission.”
image source from：spacenews
