Japan’s SLIM moon lander enters a dormant state as lunar night comes

Japan’s SLIM moon lander has entered a dormant state for two weeks on Wednesday night, January 31, 2024, as a long lunar night has come to the landing site.

The spacecraft landed on the slope of Shioli crater on the lunar surface. The coordinates of the landing site are 13.3°S, 25.2°E, with an elevation of minus 2,992 feet (minus 912 meters). So it’s near to the lunar equator.

According to the statement of Japan’s space agency (Jaxa), “Last night (1/31 ~ 2/1) we sent a command to switch on SLIM’s communicator again just in case, but with no response, we confirmed SLIM had entered a dormant state.”

A lunar day is equal to about 29.5 Earth days. So a particular spot on the lunar surface faces sunlight for 14.75 consecutive days and then darkness for 14.75 consecutive days. So sunset occurs 14.75 days after sunrise at a particular spot on the lunar surface.

Now it’s lunar twilight (dusk) at the landing site, and as a result, the spacecraft’s solar cells are not getting power.

SLIM was not designed for the harsh lunar nights as there was no nuclear power. Lunar nighttime temperature drops to about -208°F (-130° C) so there is a possibility that the solar cells will be completely dead.

However Japan’s space agency (Jaxa) will try to wake up the spacecraft from mid-February, when the Sun will shine again on SLIM’s solar cells.

The spacecraft has taken the following final image of the lunar surface before dusk.

The SLIM spacecraft captured the final image of the lunar surface before entering its dormant state
The SLIM spacecraft captured the final image of the lunar surface before entering its dormant state. (Image credit: JAXA)

The SLIM spacecraft was supposed to operate on the lunar surface for one full lunar day, i.e., 14.75 days. However, it didn’t act as planned because its landing was not smooth.

One of the two main engines stopped working prior to landing. As a result, the spacecraft landed successfully, but its solar cells were facing west.

After landing, the spacecraft was not generating power as the sun shone from the east and the solar cells were facing west. It worked only for about three hours after landing until its internal battery dipped down to 12%.

The spacecraft woke up about a week after landing on January 28, 2024, when the sun beamed down on the solar cells from the west.

So the spacecraft was operational only for about three days, from January 29 to January 31, before entering its dormant state.

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Ashim Chandra Sarkar founded Space & Telescope in 2022. He holds a M.Sc. in physics and has five years of research experience in optical astronomy. His passion for astronomy inspired him to open this website. He is responsible for the editorial vision of spaceandtelescope.com.

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