Jeng-Lun Chiu (NTHU); Chien-Ying Yang (NTHU); Che-Yen Chu (NTHU); Yi-Chi Chang (NTHU); Hung-Hsiang Liang (NTHU); Hsiang-Kuang Chang (NTHU); Steven E. Boggs (UCSD, UCB); the COSI Collaboration (UCB, LBNL, NTHU, AS, NCU, IRAP)
The Compton Spectrometer and Imager (COSI) is a balloon-borne soft gamma-ray (0.2-5 MeV) telescope designed to study astrophysical sources of nuclear line emission and gamma-ray polarization. The heart of COSI is a compact array of cross-strip germanium detectors (GeDs), providing excellent spectral resolution (0.3% at 662 keV) and capability of tracking photon scattering history with full 3D position resolution of less than 2 mm^3 for each interaction. COSI achieved a very successful flight, which was launched from Wanaka, New Zealand, in May 2016 on a Super Pressure Balloon (SPB) floating for 46 days. During this flight, COSI discovered GRB160530A and detected several sources, including the Crab, Cen A, Cyg X-1, and the 511-keV emission from the galactic center. Here I will present characteristics and capabilities of this novel instrument and current progress of this project since the 2016 SPB flight.