Cluster Launch of Hodoyoshi-3 and -4 Satellites from Yasny by Dnepr Launch Vehicle

Two Earth observation microsatellites, Hodoyoshi-3 and -4 developed by the University of Tokyo, were successfully launched into Sun Synchronous Orbit by Dnepr launch vehicle from Yasny launch base in Russia on June 19th, 2014 in order to demonstrate innovative Japanese microsatellite technologies. The launch was a part of a challenging Dnepr cluster mission of 33 satellites involving 17 countries with a variety of international cooperation. Coordination works on the launch vehicle interfaces started from a Kick-off meeting in June 2012, then PDR to CDR in 2013, and Fit-check/combined tests in March 2014. A special air-gun type shock tester was used for satellite qualification to simulate the separation shock of the vehicle. The launch campaign started with air cargo transportation of the satellites and GSE from Tokyo to Yasny via Europe in May 2014. The launch base support in Yasny proceeded to satellite check-out, installation of Li-ion batteries to the satellites, fuelling of H2O2, activation of MIPS, satellite integration onto the Space Head Module of the Dnepr vehicle, and then launch observation. The launch environment and interface constraints of the Dnepr vehicle were modest and gave favorable design flexibility to Hodoyoshi satellites, which enabled remarkable in-orbit challenges. This paper presents the critical steps of launch interfaces and experiences gained from the coordination works and launch campaign.