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Japan Set to Launch Lunar Lander, X-ray Observatory

By Doug Messier
Parabolic Arc
August 25, 2023
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Japan Set to Launch Lunar Lander, X-ray Observatory
Illustration of JAXA’s SLIM lander descending to the lunar surface.
Image credit: JAXA.

Japan will join the group of nations headed for the Moon next week when it launches a spacecraft designed to make a precision landing on the lunar surface.

The Smart Lander for Investigating the Moon (SLIM) spacecraft is scheduled for launch aboard a H-IIA on Monday, August 28 at 9:26:22 AM JST (00:26:22 UTC /8:26:22 PM EDT on August 27). The Japan Aerospace Exploration Agency (JAXA) will webcast the launch from the Tanegashima Space Center on its YouTube channel.

SLIM is a rideshare payload on the flight. The booster’s primary payload is the X-Ray Imaging and Spectroscopy Mission (XRISM), a collaboration of JAXA and NASA, in which the European Space Agency (ESA) is also participating.

XRISM’s objective is “to investigate celestial X-ray objects with high-resolution spectroscopy and high-throughput imaging,” NASA said on its website. “XRISM is expected to provide breakthrough results in diverse scientific areas, including the evolution of the universe’s largest structures, the behavior of matter in extreme gravitational fields, the spin of black holes, the internal structure of neutron stars, and the detailed physics of particle jets.”

SLIM is an irregularly shaped lander 2.4 meters (7.9 ft) in height, 2.7 meters (8.9 ft) in width, and 1.7 meters (5.6 ft) deep. Also, JAXA decided to reduce the lander’s weight by attaching the propellant tank as part of the main structure of the lander. The lander uses lightweight thin-film solar cells and lithium-ion batteries.

SLIM is a technology demonstrator designed to test the ability to perform pin-point landings while detecting and avoiding obstacles on the lunar surface. The goal is to execute an extremely precise landing, with the spacecraft touching down within 100 meters (328 feet) of its target, the ejecta blanket of Shioli crater.

JAXA selected Shioli crater because scientists believe part of the Moon’s mantle is exposed on the surface there. SLIM will use a multi-band camera to examine the composition of the mantle material, which is known as olivine, to learn more about how the Moon formed and evolved, according to JAXA’s website.

SLIM will spend three to four months traveling to the Moon before entering a 600 x 15 km (373 x 9.3 mile) orbit. It will then spend one month in orbit before attempting a landing, JAXA said.

The spacecraft will use technology adapted from facial recognition systems to identify lunar craters, and utilize images collected by JAXA’s SELENE (Kaguya) orbiter to determine its position. SLIM will search for obstacles at an altitude of 50 m (164 ft). As the spacecraft descends, the main engine will cut off at 3 m (9.9 ft) and the lander will drop to the surface. The landing system will use a 3D-printed crushable aluminum foam base to absorb the impact.

How the LEV-2 rover will move across the lunar surface. Image credit: JAXA/Tomy Company/Sony/Doshisha University.

SLIM will then deploy the Lunar Excursion Vehicle 1 (LEV-1), which is a 2.1 kg (4.6 pound) lunar hopper measuring 26 x 40 x 30 cm (10.2 x 15.7 x 11.8 in). LEV-1 will transmit data directly to Earth as it moves across the surface.

SLIM is also carrying the Lunar Excursion Vehicle 2 (LEV-2), a tiny, ball-shaped rover with a diameter of 8 cm (3.1 in) and a mass of 250 g (8.8 ounces). LEV-2 is equipped with two cameras and will change its shape in order to move across the surface. The rover was designed by JAXA in cooperation with the Tomy Company, Sony Group Corporation, and Doshisha University.

If successful, SLIM will be the first Japanese spacecraft to land on the Moon. Hakuto-R lander, launched by the private Japanese company ispace, crashed on the Moon during descent on April 25, 2023.

LEV-2 in the crawling mode, swinging from side to side. Image credit: JAXA.

It’s been a mixed year for Moon landings. Russia’s Luna-25 lander crashed on August 19 when its engine fired too long while lowering the spacecraft’s orbit. India had more success four days later when its Chandrayaan-3 lander successfully touched down on the surface.

This will be the third launch by Japan in 2023. A H-IIA rocket launched the IGS-Radar 7 reconnaissance satellite for the Japanese government on January 26.

The maiden flight of the nation’s new H3 launch vehicle on March 7 did not go as well. Controllers sent a destruct command to the booster after its second stage failed to fire. JAXA’s ALOS-3 remote sensing satellite was destroyed in the accident.

One response to “Japan Set to Launch Lunar Lander, X-ray Observatory”

  1. lopan says:

    Long past time JAXA took a risk. They can do this stuff, but they usually just don’t feel like it.

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