OAOWFC: Okayama astrophysical observatory NIR wide-field camera

In order to detect and trace the early phase of near-infrared (NIR) afterglows of Gamma Ray Bursts (GRBs) quickly, we are now developing the Okayama Astrophysical Observatory Wide-Field Camera, OAOWFC. The aperture size of OAOWFC is 91cm. The focal plane is covered by a 2Kx2K RAWAII2-RG detector with a pixel size of 18.5 mu m x 18.5 mu m, resulting 0.95 x0.95 deg(2) field of view with an image scale of 1.6 arcsec/pixel. OAOWFC is designed to be a fully robotic instrument. This camera forms a part of Multicolor Imaging Telescopes for Survey and Monstrous Explosions (MITSuME), a multi telescope system dedicated to optical-NIR follow-up observations of GRB afterglows. Very wide field of view of OAOWFC enables us to catch GRB afterglows under less accurate localization sometimes given by the first alert. OAOWFC has an ability to detect bright GRB afterglow located at z=10 easily, and it might be detectable at z=18 if the conditions are met.