SLIM — an acronym for Smart Lander for Investigating Moon — is a compact robotic spacecraft that is about the size of a small food truck. It weighed more than 1,500 pounds at launch. The Japanese space agency, JAXA, nicknamed it “moon sniper.”
Since its launch in September (sharing a ride to space with XRISM, an X-ray telescope), SLIM has been taking a slow but fuel-efficient route to the moon. It entered orbit on Dec. 25 after a 110-day trip.
The spacecraft’s initial elliptical orbit stretched as far as 2,500 miles from the moon. A firing of SLIM’s engines on Jan. 14 lowered it to a circular orbit about 370 miles above the surface.
SLIM is aiming to set down close to a small crater named Shioli in the equatorial region of the moon’s near side.
If it lands successfully, it will deploy two unconventional rovers, called Lunar Excursion Vehicle 1 and Lunar Excursion Vehicle 2. One uses a hopping mechanism and carries a thermometer, a radiation monitor and an instrument for measuring the slope and elevation.
The second rover is spherical, about the size of a baseball and half a pound in weight. Its two halves will pull apart, allowing the rover to crawl along the surface for a couple of hours until its battery is exhausted. JAXA developed this rover in cooperation with Doshisha University and Tomy, a toy company.
SLIM’s primary mission is not scientific, but an instrument on the lander will allow scientists to measure the composition of nearby rocks.
