Japanese Moon lander SLIM successfully reaches lunar orbit on Christmas

If SLIM sticks the soft landing, Japan will become the fifth country to land a robotic mission on the Moon. The landing is on target for Jan. 20, according to JAXA.

Japan's lunar lander began its orbit of the Moon on Monday, setting the nation up for its first Moon landing in the coming weeks. 

The Japanese Aerospace Exploration Agency's Smart Lander for Investigating Moon (SLIM) mission launched along with the X-Ray Imaging Spectroscopy Mission (XPRISM) in September from Japan. XPRISM continues to orbit Earth. Meanwhile, SLIM headed out on a lunar orbital insertion trajectory arriving in Moon orbit on Christmas. 

"The Japan Aerospace Exploration Agency (JAXA) is pleased to announce that the Smart Lander for Investigating Moon (SLIM) was successfully inserted into lunar orbit at 16:51 (Japan Standard Time, JST) on Dec. 25, 2023," the space agency said in a news release.

SLIM will continue an elliptical orbit around the Moon's poles about every 6 hours, reaching 372 miles above the surface at its closest point in orbit. In mid-January, SLIM's spaceflight will change to a circular orbit and begin to lower in preparation for landing, according to JAXA. 


JAXA said the mission is going well, and because of the "smooth progress of operations," the lunar landing sequence is scheduled to begin on Jan. 20 around midnight JST, with the lunar landing expected about 20 minutes later.

A slim landing zone

The Japanese mission has two objectives: "achieve a small-scale lightweight probe system and pinpoint landing technology." JAXA said it hopes to achieve a landing accuracy of 100 meters compared to several or dozens of kilometers of "conventional lunar landers."

The spacecraft will use vision-based navigation, taking photos along the descent to measure and correct its position. If SLIM lands within this radius, that will be a fully successful mission for Japan, and any continued operation on the lunar surface will be a bonus. 

SLIM has two probes that will be spit out onto the lunar surface to help communicate with Earth and monitor mission status after the landing. 

SLIM's targeted landing zone is near the Shiloi impact crater within the Sea of Nectar region on the near side of the Moon. 

The agency said the mission will help shape future landings for humans and other robotic missions to the Moon and beyond. 

A robotic landing on the Moon is a high-risk mission. While Japan has not landed on the Moon before, it has successfully touched down on two asteroids with its Hayabusa spacecraft. JAXA said lunar landing is more challenging because the gravity on asteroids is lower than on the Moon and Earth. 


Only four countries have successfully landed missions on the Moon, including the U.S., the Soviet Union, China and, most recently, India. Since the space era began in the 1950s, just over half of all landing attempts have been successful.

In the New Year, two American companies will attempt to be the first private landings on the lunar surface as part of NASA's Commercial Lunar Payload Services (CLPS) program.