The COS-B experiment for gamma-ray astronomy

The COS-B satellite will carry a single large experiment capable of detecting gamma-rays with energies in excess of 20 MeV in order to study in detail the sources of extraterrestrial gamma-radiation. The experiment features a 16-gap spark chamber for the identification and determination of the arrival direction of the gamma quanta, a caesium-iodide energy calorimeter for energy determination, a telescope defining the field of view of the experiment, and a plastic-scintillator anticoincidence shield for the rejection of charged particles. Also included is a proportional counter sensitive to x-rays in the 2.12 keV range, to synchronize on the possible short-period pulsations of gamma-ray emission from sources detected to pulsate at x-ray wavelengths. The eccentric orbit will permit observations for 80% of each orbital period, when the satellite is outside the radiation belts. The attitude control and measurement system enables the experiment to be pointed in almost any desired direction with the attitude known to better than 0.5 deg. An operational life of two years is foreseen so that 24 targets can each be studied for approximately one month