Two cameras point normally to the rotation axis to the same direction, so that their error boxes cross each other, therefore reducing the positioning error to for weak sources and to for stronger sources; it has a 20 mCrab sensitivity. the third camera points along the rotation axis. Each observation lasts about 100 s; then, the next pointing is obtained with a rotation and so on, untill a complete rotation is performed (every 100 min), during which 80% of the whole sky has been monitored. This capability in monitoring possible X-ray transients and variations in flux of known sources, like CygX-1, makes the ASM experiment suitable for detecting GRBs; nevertheless, the small collecting area and the small field of view limit the number of localized bursts. Moreover, when a GRB is within the field of view of one camera, its direction is known only along one dimension, given the large width ( ) of the error strip; therefore, although it cannot precisely locate GRBs by itself, nevertheless it can be very important in reducing the error box, when other experiments detected the same burst: this occurred in several cases ([Smith et al., 1999]).