Development of a terahertz short range imaging model

A ray trace model was developed to simulate atmospheric effects upon short range imaging of a scene for a narrow frequency band centered at 650 GHz. The frequency chosen is in the vicinity of a terahertz frequency band atmospheric window. We describe the assumptions that went into this model, including the statistics for the density distribution of atmospheric water vapor, which is one of the main molecular absorbers in this spectral region. We also summarize the results of a measurement program in which point sensors (with a 20 Hz sampling rate) measured wind-advected water vapor density. We examine the validity of the atmospheric absorption statistics assumed in our imaging model through a spectral analysis of the temporal series for absorption coefficient derived from the water vapor density data.