2 Selection on coordinates

The satellite attitude is constrained by the requirement that the solar panels face a direction within 30$^{\circ}$ from the Sun direction. In addition, for the first year of operation, during the NFI primary pointings the WFCs were preferentially pointed as close as possible to the Galactic plane. These two facts resulted in a non-uniform sky coverage by the WFC, and consequently in a non-uniform sky distribution (Fig. 1) of the BeppoSAX/WFC well-localized GRBs. A further selection favours the celestial poles because for these high latitudes the periodic Earth occultation of the WFC field of view, due to the satellite orbital motion, is shorter, making the net WFC exposure time at these directions longer than at equatorial directions.

  

Figure 1: Sky distribution of the BeppoSAX GRBs (as of November 1998) in Galactic coordinates, showing the non-uniform distribution