In September 2015, a team of astronomers successfully observed the entire hydrogen coma of the comet 67P/Churyumov-Gerasimenko, using the LAICA telescope onboard the PROCYON spacecraft. They also succeeded in obtaining the absolute rate of water discharge from the comet. Through our observations, we were able to test the coma models for the comet for the first time. This result is the first scientific achievement by a micro spacecraft for deep space exploration.