During the time interval scanned by the off-line quest, i.e. July 3, 1996 - October 3, 2001, the on-board logic was triggered by 15,857 events; out of them, after this off-line quest, only 693 could not have been scanned, because of the proximity to data gaps, mainly connected with the SAGA (this number, i.e. 693, is smaller than the 1032 taken in sec. , because that was for the 1 s quest only: in this case, the number is smaller because several on-board triggers missed by one particular quest, have been scanned with other rebin times, instead; therefore, the final number of 693 unscanned on-board triggers refer to those events, that could not have been scanned by any quest).
Thus, if one takes into account only those on-board triggers that
have been scanned by at least one kind of off-line quest
(1 s, 2 s, 4 s, or 8 s, resp.), i.e.
15,857 - 693 = 15,164 triggers, the reliability
on-board trigger logic can be defined as the ratio of the
number of true GRBs that triggered the GRBM on board, over the
number of scanned on-board triggers:
The estimate coming out from eq. relies on the assumption that all the on-board triggers that have been automatically scanned by the off-line quest and that have not been classified as GRBs, cannot be GRBs. On the other hand, from table , it is known that there are at least 5 exceptions (4 in common with BATSE and 1 with one WFC); however, in the next sections, when dealing with the common sample with BATSE, it will be shown that this fraction still remains negligible, so that the above assumption is still reasonable.