MODTRAN on supercomputers and parallel computers. To enable efficient reduction of large data sets such as is done in the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) project at the Jet Propulsion Laboratory (JPL), a high performance version of MODTRAN is essential. One means to accomplish this is to apply the computational resources of parallel computer systems. In our present work, a flexible, parallel version of MODTRAN has been implemented on the Cray T3E, the HP SPP2000, and a Beowulf-class cluster computer using domain decomposition techniques and the message passing interface library. In this paper, porting the sequential MODTRAN to various platforms is discussed; strategies of designing a parallel version of MODTRAN are developed; detailed implementation for a parallel MODTRAN is reported, and performance data of the parallel code on various computers are presented. Near linear scaling performance of parallel MODTRAN has been obtained, and comparisons of wallclock time are made among various supercomputers and parallel computers. The parallel version of MODTRAN gives excellent speedup, which dramatically reduces total data processing time for many applications such as the AVIRIS project at JPL.