Current Progress of the Compton Spectrometer and Imager (Cosi) Project Since the 2016 Flight
Jeng-Lun Chiu1*, H.-K. Chang1, S. E. Boggs2, A. Lowell2, C. A. Kierans2, C. Sleator2, J. A. Tomsick2, A. Zoglauer2, C.-Y. Yang1, C.-Y. Chu1, C.-H. Tseng1, M. Amman3, C.-H. Lin4, P. Jean5, P. von Ballmoos5
1Institute of Astronomy, National Tsing Hua University, Hsinchu City, Taiwan
2Space Sciences Laboratory, UC Berkeley, Berkeley, CA, USA
3Lawrence Berkeley National Laboratory, UC Berkeley, Berkeley, CA, USA
4Institute of Physics, Academia Sinica, Taipei City, Taiwan
5IRAP Toulouse, 9 avenue du Colonel Roche, Toulouse, France
* Presenter:Jeng-Lun Chiu,
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 mm3 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.

Keywords: Compton telescope, gamma-ray, polarization, GRB, Crab , germanium detector, balloon, spectrometer, imager