ABSTRACT
The idea of using air fluorescence to detect the passage of extensive air showers (EAS) through the atmosphere occurred independently to Greisen in 1960 and to Delvaille, et al., and Suga and Chudakov in 1962. Isotropically emitted fluorescence light from extensive air showers (EAS) is detected by those tubes whose solid angle intersects the EAS. The relative time of arrival of this light, as well as the total integrated light, are recorded for each tube. The detector is triggered when a minimum number of adjacent tubes fire within a preset gate width. The trigger interrupts a computer, and relative times and pulse height integrals for those tubes which fired within the trigger gate are read out. A considerably simpler technique for reconstructing the EAS trajectory has recently been implemented by the "Fly's Eye" group. They have constructed a second "Fly's Eye," with 36 mirrors, approximately 3.5 km from the first.
