T. Tanimori, H. Kubo, J. D. Parker, T. Mizumoto, Y. Mizumura, T. Sawano, K. Nakamura, Y. Matsuoka, S. Komura, S. Nakamura, T. Kishimoto, M. Oda, T. Takemura, S. Miyamoto, K. Miuchi, S. Kurosawa
Over ten years from COMPTEL mission, an MeV gamma-ray window does not open, because there is a serious problem which observations are obstructed by a huge background. COMPTEL tried to reject background with time of flight between a scatterer and an absorber, but it was not enough to obtain a designed sensitivity. The unique solution for background suppression is electron-tracking. By the electron-tracking, we can reconstruct Compton-scattering completely. In addition, the electron-tracking provides two independent background-suppression methods: 1) Compton-kinematics test using the angle between scattering direction and recoil direction, and 2) particle identification using the energy deposit rate. Utilizing the advantages of the electron-tracking, we are developing an electron-tracking Compton camera (ETCC) using a gaseous electron tracker. The results of first balloon flight and the experiment in the strong radiation field using a proton beam proved that our ETCC has a powerful background rejetion ability, and it can detect gamma-ray sources with a good signal to noise ratio. If four ETCCs using 50 cm-cubic electron trackers with 3 atm Xe gas loaded on a satellite, the detection sensitivity will reach to 1 mCrab, which is 100 times higher than that of COMPTEL. Moreovre, our ETCC can detect >10 MeV using electron-positron pair tracking with a good angular resolution, so that an ETCC will realize a precise sky survey in multi energy band. In this presentation, we report the performance of the current ETCC and the future plan.