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The Atmospheric Transmission Large-Area Analysis System (ATLAS) system has been used by the West Desert Test Center (WDTC), Dugway proving Ground, UT since 1994 to assist in the characterization of aerosol clouds. The ATLAS is a tool for measuring transmittance through aerosol clouds in the far infrared (8-14 mu m) spectral region. ATLAS is a passive single-ended system employing a thermal imager for data collection and uses the natural background as the reference source. The final ATLAS product is a two-dimensional transmission map of the aerosol cloud as seen by the imager. Historically ATLAS data reduction and map production has been a lengthy process. This process includes transportation of the infrared video tapes from the field test site to the WDTC Optical Data Laboratory, digitization of infrared tapes, and subsequent image processing of the video frames to produce transmission maps as a function of time. In order to significantly reduce data processing and delivery time, the WDTC and Science and Technology Corporation have developed the Real-Time ATLAS (RT-ATLAS) system. RT-ATLAS is a field-portable system that reduces data turn-around time from days to real-time for approximate results and to tens of minutes for final products. This paper describes the physics of the ATLAS technique, the physical RT-ATLAS system, and new enhancements to the ATLAS system. Data examples and analysis are presented and RT-ATLAS strengths and limitations are discussed.