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Planetary News: Kaguya (SELENE) (2007)

“Lunar A” to Stay on Earth

By Amir Alexander
19 January 2007
Lunar A at the Moon
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Lunar A at the Moon
This artist's depiction shows Lunar A as it is releasing one of its penetrators. Credit: JAXA

The Japanese space agency JAXA has recommended that the Lunar A mission to the Moon be cancelled. Originally scheduled to launch in 1995, Lunar A was repeatedly delayed by unforeseen technical difficulties. When its last scheduled launch in 2004 passed and the spacecraft was still not ready, JAXA listed the mission as “postponed.” On January 15, 2007, a spokesman announced that the agency had now concluded that the mission should be scrapped.

Lunar A was to be composed of a mother ship and two torpedo-shaped penetrators, each 80 centimeters long and 16 centimeters in diameter. The penetrators were to be dropped from the spacecraft on opposite sides of the Moon – one on the near side and one on the far side. Each would strike the surface at high speed, burying themselves to a depth of 1 to 3 meters. From this position they would use their highly sensitive seismometers to monitor Lunar seismic activity and send their findings to the mother ship when it passed overhead. The spacecraft would in turn relay the data to Earth.

The positioning of the two penetrators on opposite sides of the Lunar globe was critical for the mission's success. Scientists believe that the difference in time it would take a seismic tremor to reach each of them would provide important clues to the internal composition of the Moon. When combined with data gathered from surface seismometers put in place by Apollo astronauts decades ago, scientists hoped to get a good picture of the different layers that make up the Moon’s interior. In addition, the penetrators carried instruments designed to measure heat flow on the Moon, and the mother ship was equipped with a camera to take high resolution images of the Lunar surface.

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But it was not to be. While the mother ship was ready on time in 1995, building the penetrators proved to be a much tougher technological challenge than had been expected. Time after time the penetrators failed their tests, prompting revisions and redesigns. By all accounts the penetrators are now very close to being ready, but the mother ship, in storage since 1995, has fallen into disrepair. Repairing the ship would require a major investment in a mission that is already far over budget, and JAXA therefore concluded that the mission be cancelled. A final decision by the Japanese Space Activities Commission is expected in early February.

The end of Lunar A may not spell the end for the penetrators that took so long to develop. JAXA hopes these will ultimately be used in a future Lunar or planetary mission. If no Japanese mission will find a place for them, JAXA intends to offer the technology to other space agencies.

In the meantime, Japan’s plans for a mission to the Moon continues with SELENE – a more capable and ambitious spacecraft than Lunar A. It is scheduled for launch this summer.