We use the CORSIKA air shower simulation program to review the method for a
ssigning energies to ultra-high energy cosmic rays viewed with the air fluo
rescence technique. This technique uses the atmosphere as a calorimeter, an
d we determine the corrections that must be made to the calorimetric energy
to yield the primary cosmic-ray energy. (C) 2000 Elsevier Science B.V. All
rights reserved.