Up until 2002, the DIRSIG model was focused on simulating passive multi-spectral and hyper-spectral sensing systems in the visible through thermal infrared regions. At that time, the ability to perform trade studies between passive and active laser radar systems would require the use of separate modeling packages that may use different geometric, optical and thermodynamic descriptions. In addition, the state-of-the-art LIDAR scene simulation tools did not support rigorous atmospheric interactions, participating mediums, multiple bounce/scattering, thermal and reflective region passive returns, complex scene geometries, moving platform and scanning effects, detailed material optical descriptions (BRDF and scattering models) and time-gated returns.
The benefits of an integrated active LIDAR and passive multi- and hyper-spectral simulation environment that leveraged a unified set of model inputs and underlying radiation propagation models would be significant. Such a tool would allow users to simulate active and passive sensors using the same scenes and scenarios and allow for the evaluation of passive versus active approaches to specific problems and the exploration of data fusion between these two imaging paradigms.