Remote detection of bioparticles in the THz region

Recent measurements of the electromagnetic transmission through Bacillus subtillus, an innocuous anthrax substitute, have revealed absorption resonances in the THz region. A system-level analysis is carried out to show that at least one of the resonances (centered at 14.05 cm/sup -1/, or 421 GHz) is located at a frequency of low enough atmospheric absorption to be detectable by an active remote sensor - a differential absorption radar.