After the accidental discovery by the Vela satellites the search for GRBs continued with small experiments on-board the later on-going space missions. GRB experiments flew on-board: Orbiting Geophysical Observatory 3 and 5; Orbiting Solar Observatory 6, 7 and 8; Apollo 16; Solrad 11A and 11B; Helios 2; Prognoz 6 and 7; Pioneer Venus Orbiter; International Sun Earth Explorer 3; the KONUS and SIGNE experiments on-board Venera 11 and 12 and Wind; SIGNE 3; Solar Maximum Mission; HEAO-1; the MIR space station; GINGA; WATCH and SIGMA on-board GRANAT and EURECA; Ulysses; TGRS on Wind. The output of these experiments were limited catalogues of events, with some of them localized at the arcmin precision.
The first experiment dedicated to the systematic study of the GRBs is the BATSE experiment on-board the Compton Gamma Ray Observatory. It was conceived to study the angular distribution of the arrival directions in order to associate it, or not, to the distribution of known objects in our Galaxy. The strategy chosen by BATSE was to detect a large number of GRBs, localizing them with a precision from few to tens of degrees. In fact BATSE has already detected about 2.200 GRBs and continue on detecting them at a rate of about six per week.
Given the excellent but not resolutive results achieved by the previous experiments, a new mission was conceived, dedicated to the study and prompt reaction to GRBs. This mission, High Energy Transients Explorer (HETE) ([Ricker et al. 1997]), was launched at the end of 1996, but the deployment of the payload failed. The results achieved by BeppoSAX indicate that the HETE concept was correct and therefore the satellite is scheduled be launched again on 1999 as HETE-2.