PROCYON(Proximate Object Close flyby with Optical Navigation) was an asteroid flybyspace probethat was launched together withHayabusa2on 3 December 2014 13:22:04 (JST). It was developed byUniversity of TokyoandJAXA.
It was a small (70 kg, approx. 60 cm cube), low cost (¥500 million) spacecraft.[1]
PROCYON was launched as secondary payload together with theHayabusa2asteroid landing probe. After separation from the carrier rocket, PROCYON was left on aheliocentric orbit.On 22 February 2015, the ion engine was started, with the intention of adjusting the orbit so that an Earth flyby in December 2015 would direct the probe towards asteroid2000 DP107.[3]Initial results were favourable - the engine delivered 330 μN of thrust rather than the designed 250 μN - but the engine failed on 10 March and could not be restarted; PROCYON flew past Earth on 3 December 2015, but was unable to make a controlled orbit change. Shortly after the Earth flyby, contact with the spacecraft was lost.[4]
The 70 kg spacecraft had a specific impulse of 1000 seconds, for a delta-V budget of about 500 ms−1;the intention was to use 20% of the xenon propellant for the initial orbit correction, and the rest of the propellant between the Earth flyby and the asteroid flyby to ensure a controlled flyby distance of 30 km.[5]
A novel subsystem tested by PROCYON involved feeding both the main ion engine and the eight cold-gas attitude control thrusters from the same tank (containing 2.5 kg of xenon at launch)
PROCYON observed theLyman- Alphaemission of comet67P/Churyumov–Gerasimenkoto determine its overall coma structure.[7]PROCYON captured the first complete image of thegeocorona,confirming for the first time that it has north-south symmetry.[8]
Launches are separated by dots ( • ), payloads by commas (, ), multiple names for the same satellite by slashes ( / ). Crewed flightsare underlined. Launch failures are marked with the † sign. Payloads deployed from other spacecraft are (enclosed in parentheses).
