Author/Authors :
Oshima، نويسنده , , A. and Dugad، نويسنده , , S.R. and Goswami، نويسنده , , U.D. and Gupta، نويسنده , , S.K. and Hayashi، نويسنده , , Y. and Ito، نويسنده , , N. Kannan Iyer، نويسنده , , A. and Jagadeesan، نويسنده , , P. and Jain، نويسنده , , A. and Kawakami، نويسنده , , S. and Minamino، نويسنده , , M. K. Mohanty، نويسنده , , P.K. and Morris، نويسنده , , S.D. and Nayak، نويسنده , , P.K. and Nonaka، نويسنده , , T. and Ogio، نويسنده , , S. and Rao، نويسنده , , B.S. and Ravindran، نويسنده , , K.C. and Tanaka، نويسنده , , H. and Tonwar، نويسنده , , S.C.، نويسنده ,
Abstract :
The absence of a well established point source of very high energy ( ≳ 10 TeV ) γ-rays in the sky, makes the measurement of the angular resolution and the absolute pointing accuracy of an extensive air shower (EAS) array a challenging task. In the past, several groups have utilized the reduction in the isotropic flux of cosmic rays due to the shadows of the Moon and the Sun, to measure the angular resolution and the absolute pointing accuracy of their arrays. The data collected from the GRAPES-3 EAS array, over the period of 4 years from 2000 to 2003, has been used to observe the shadow of the Moon at a level of ∼ 5 σ and that of the Sun at a lower level of significance. The high density of the detectors in GRAPES-3 enabled an angular resolution of 0.7° to be obtained at energies as low as 30 TeV. The angular resolution studies were further extended by using two other techniques, namely, the even–odd and the left–right methods. All three techniques have yielded nearly identical results on the energy dependent angular resolution.
