NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header




PROCYON, the PRoximate Object Close flYby with Optical Navigation, is a small satellite launched as a secondary payload with Hayabusa 2. Unfortunately, the ion engine malfunctioned on 10 March 2015. The spacecraft was to make a close flyby of asteroid 2000 DP107. The principal objectives of PROCYON were demonstration of a deep space exploration micro-satellite bus system; power generation, thermal control, attitude control, communication, and orbit determination in deep space; and orbit control by a small electric propulsion system. The secondary goals included communication using a high-efficiency GaNX-band power amplifier; precise delta differential one-way range determination (DDOR) navigation in deep space; optical navigation to encounter an asteroid; and asteroid close flyby observations.

Spacecraft and Subsystems

The spacecraft body is cube-shaped, 67 x 55 x 55 cm, with four solar panels, each roughly a 47 x 47 cm square, extending from the top. Total dry mass of the spacecraft is 65.5 kg, with an additional (approximately) 2 kg of xenon for propulsion. Mounted on the top of the spacecraft are a flat X-band high gain antenna and two small isoflux X-band low-gain antennae, one for uplink and one for downlink. An identical set of low gain antennae are mounted on the bottom. A flat X-band medium gain antenna is mounted on one of the sides. Communications are via a 15-W GaN-based solid state power amplifier and X-band transponder.

Attitude control is achieved with 8 Xe cold gas thrusters, each 19 mN. All are mounted along the center of the intersections between the faces of the cube, four on the sides, two on top, and two on the bottom. There are four reaction wheels, a 3-axis Fiber Optic Gyro, a star tracker, and five non-spin Sun aspect sensors. The main Xenon ion thruster, 250 microNewtons, is mounted (non-gimbaled) on one side of the spacecraft body. One of the bottom corners holds a rotatable telescope, which is used for navigation and asteroid observation.

Mission Profile

PROCYON was launched with Hayabusa 2 on 3 December 2014 at 04:22:04 UT (13:22:04 local Japanese Time) from the Tanegashima Space Center on an H2A rocket. The ion engines were started on 22 February but failed on 10 March and could not be restarted. It could not control its Earth gravity-assist swingby on 3 December 2015 and could not make its planned 2016 asteroid flyby. It was able to make observations of Comet 67P/Churyumov-Gerasimenko in September 2015.

Alternate Names

  • 40322

Facts in Brief

Launch Date: 2014-12-03
Launch Vehicle: H-2A
Launch Site: Tanegashima, Japan

Funding Agency

  • Japan Aerospace Exploration Agency (Japan)


  • Other

Additional Information

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



NameRoleOriginal AffiliationE-mail
[] NASA Logo -