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EQUULEUS (EQUilibriUm Lunar-Earth point 6U Spacecraft) is a 6U cubesat designed to reach an Earth-Moon libration orbit. It is a JAXA (Japan) and University of Tokyo technology demonstration mission with the primary objective of demonstrating trajectory control techniques exploiting Sun-Earth_Moon dynamics, wit the possibility of reaching an Earth-Moon libration orbit. It will also perform scientific observations with a suite of instruments. The primary objectives of these studies are to observe the Earth's plasmasphere in the ultraviolet band; characterize the dust environment in cislunar space; and record lunar impact flashes. EQUULEUS will be launched as a secondary ride-on satellite on the Artemis 1 Space Launch System.

Spacecraft and Subsystems

EQUULEUS is a 6U cubesat with dimensions 10 x 20 x 30 cm and a mass of approximately 11.5 kg. Power (50 W at 1 AU) is provided by two deployable solar arrays and batteries. Propulsion and attitude control are achieved using the AQUARIUS system, a warm gas propulsion system with water as the propellant. The system comprises 8 water thrusters, with a planned thrust of 3.3 mN and an Isp of 70 seconds. Total mass of water propelled is 1.22 kg, providing a total delta-v of 77 m/s. Communications are through an X-band transponder and one medium-gain and one large-gain antenna. EQUULEUS carries three scientific instruments: PHOENIX, an extreme ultraviolet imager; CLOTH, a dust detector; and DELPHINUS, a camera designed to detect impact flashes.

Mission Profile

After launch as a ride-on payload on the SLS with Artemis 1 on 16 November 2022, EQUULEUS was released to begin a lunar flyby sequence over a period of 1 to 3 months, followed by maneuvers exploiting Earth-Sun-Moon dynamics over 5 months. This will bring it to a libration orbit around the Earth-Moon L2 LaGrange point using a minimal amount of propellant. It will make observations from this position for about 1 month before the mission ends.

Alternate Names

  • 55905
  • EQUilibriUm Lunar-Earth point 6U Spacecraft

Facts in Brief

Launch Date: 2022-11-16
Launch Vehicle: SLS Block 1 Crew
Launch Site: Cape Canaveral, United States
Mass: 11.5 kg
Nominal Power: 50 W

Funding Agency

  • Japan Aerospace Exploration Agency (Japan)


  • Planetary Science
  • Engineering

Additional Information

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



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