Discovery of GRBs. Gamma-ray bursts were serendipitously discovered by the nuclear test-ban monitoring satellites Vela (US), (Figure 11.1) and Konus (USSR). Soon afterwards, it became clear that these events were not thermonuclear experiments of terrestrial origin, but rather a new astrophysical transient in the sky. These data were first released in 1973 by R. Klebesadel, I. Strong and R. Olson[296] and in 1974 by E. P. Mazets, S. V. Golenetskü and V. N. Ilinskii[368]. The first detection of a gamma-ray burst in the Vela archives is GRB 670702 (Figure 11.2). In the footsteps of Vela and Konus, a number of other gamma-ray burst detection experiments and missions were conducted[12]: Apollo 16, Helios 2, HEAO-1, International Sun Earth Explorer 3, Orbiting Geophysical Observatory 3 and 5, Orbiting Solar Observatory 67–8, Prognoz 6–7, Pioneer Venus Orbiter (1978–92), Konus and SIGNE on Venera 11–12 and Wind, Transient Gamma-ray Spectrometer (TGRS) on Wind, SIGNE 3, Solar Maximum Mission (1980–89), Solrad 11AB, MIR Space Station, GINGA, WATCH and SIGMA on GRANAT and EURECA, and Ulysses.