GWAC (Ground-based Wide Angle Camera)

The main science objective of the Ground-based Wide Angle Camera (GWAC) is to observe  in optical (between 500 and 860 nm) the prompt emission of GRBs detected by ECLAIRs. The GWAC will consist of 36 Ø180mm cameras, totalling a FoV of ~5000 degrees2 i.e. roughly half of ECLAIRs FoV. Each camera will be equipped with a 4096×4096 E2V CCD.


Engineering model of one GWAC module (4 cameras). The GWAC, once completed, will consist of 36 cameras. The first light is expected  in 2017. Credit: NAOC

The GWAC cameras will enable a systematic study of any optical emission prior to and during the  high-energy prompt emission phase reaching a 10s sensitivity of ~16 mag. in the V band. The characteristics of the GWAC are such that it will be a powerful tool to study the transient sky and to look for optical counterparts of gravitational wave events.

Two 60cm diameter telescopes and a network of 30cm diameter telescopes will complete the GWAC system. These robotic telescopes will promptly react to any transient source detected by the GWAC cameras and will help validating the detection.

The GWAC will be divided into two sub-sets, each of them consisting of 18 cameras and a Ø60cm  follow-up telescope. One part will be installed at CTIO in Chili and the other part at the ALI observatory in the west of Tibet.


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Auteur : CEA / Irfu & Olivier Godet