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Smart Lander for Investigating Moon

NSSDCA/COSPAR ID: 2023-137D

Description

The Smart Lander for Investigating Moon (SLIM) is a Japanese Aerospace Exploration Agency (JAXA) mission designed to demonstrate accurate lunar landing techniques by a small explorer, with the objective of acceleration of the study of the Moon and planets using lighter exploration systems. The techniques demonstrated by this mission will pave the way for future lunar sample return missions. SLIM launched on 6 September 2023 and landed on the Moon on 19 January 2024 (20 January JST).

Spacecraft and Subsystems

SLIM is an irregularly shaped cuboid 2.4 meters in height, 2.7 meters across, and 1.7 meters deep, with a dry mass of 190 kg and a fully loaded mass of 710 kg. The body is built around the propellant tank as the structural element. Power is provided by thin-film solar cells and lithium ion batteries. SLIM will carry a landing radar for the final descent and a multiband camera for mineralogical exploration of the surface, as well as a small laser retroreflector array. The landing system uses a crushable aluminum foam base to absorb impact. The propulsion system comprises two 500 N ceramic engines for orbit manuevers and twelve 22 N thrusters for attitude control. All engines and thrusters use hydrazine (N2H4)/ nitrogen tetroxide (NTO - MON-3) bipropellant, stored in a common tank separated by a bulkhead.

Lunar Excursion Vehicle (LEV) Rovers

SLIM carried two small rovers, Lunar Excursion Vehicles 1 and 2 (LEV-1 and LEV-2). LEV-1 has a mass of 2.1 kg. It was successfully deployed immediately before SLIM landed. It executed its planned hopping movements, made test communications with LEV-2, and successfully transmitted UHF band radio waves that were received on Earth. LEV-2, nicknamed SORA-Q, has a mass of 0.25 kg. It had a spherical shape with a diameter of about 8 cm at landing, and then opened into an elliptical shape with central paddles that it used to "crawl" along the surface. It was equipped with an imaging device. It also deployed prior to landing and was able to image the SLIM spacecraft on the surface.

Mission Profile

SLIM launched on September 6 at 23:42:11 UT (September 7, 8:42:11 a.m. JST) as a ride-share payload with the XRISM mission on an H2A booster from the Tanegashima Space Center in Japan. All systems were reported nominal after upper stage separation putting it on a four month journey to lunar orbit. It made a close approach, 5000 km altitude, of the Moon on October 4 at 6:47 UT and continued on an elliptical orbit that brought it back to the Moon on 25 December 2023. A thruster firing put it into a 600 x 4000 km altitude lunar polar orbit with a period of approximately 6.4 hours at 07:51 UT (16:51 JST).

Over the course of about a month it trimmed its orbit into a circular, 600 x 600 km orbit, and then lowered its perilune to 15 km. A powered descent phase brought it down to 3.5 km altitude, on 20 January 2024 at 12:00 am JST (15:00 UT, January 19). Using the onboard camera, the spacecraft position with respect to the surface was determined. It then entered the vertical descent phase, descending towards the surface. At the end of this phase, it began a program of obstacle detection, to avoid any hazards at the landing site. At about 3 meters altitude the engines cut off and the lander dropped to the surface, at approximately 12:20 am JST (15:20 UT) at 25.2510 E, 13.3160 S. The landed mass was about 210 kg, landing objective was to be within 100 meters of the target point, the ejecta blanket of Shioli crater (crater centered at approximately 13.322 S, 25.232 E).

Following landing, signals were sent from and received by SLIM, but the solar cells were not charging the batteries. JAXA reports that one of the thrusters failed at about 50 meters altitude, and although SLIM landed successfully, its solar panels ended up facing westward. (The Sun was in the east at the time of landing.) Only limited battery power was available for a few hours. SLIM was powered down at 17:57 UT when the batteries reached 12%. The LEV-1 and LEV-2 rovers successfully deployed. On January 28, sunshine reached a point where it struck the solar panels, providing power, and SLIM resumed operations and communications until lunar night. Telemetry was received after the first lunar night ended and the Sun reached the solar panels, on February 25, although the Sun set on March 1 and the spacecraft was put back to sleep. The spacecraft was again operable after its second lunar night when Sun hit the solar panels on March 26, and SLIM was able to take images and send telemetry.

The Institute of Space and Astronautical Science (ISAS) SLIM page is available at:

https://www.isas.jaxa.jp/en/missions/spacecraft/developing/slim.html

Image credit: ISAS/JAXA

Alternate Names

  • 57803
  • SLIM
  • SmartLanderforInvestigatingMoon

Facts in Brief

Launch Date: 2023-09-06
Launch Vehicle: H-2A
Launch Site: Tanegashima, Japan
Mass: 190 kg

Funding Agency

  • Japan Aerospace Exploration Agency (Japan)

Discipline

  • Planetary Science

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Shin-ichiro SakaiProject ManagerJapan Aerospace Exploration Agencysakai@isas.jaxa.jp
[SLIM image of the Moon]
Image of SLIM on the Moon taken by LEV-2 and image taken by SLIM on 3rd lunar day
(credit JAXA)

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