The Raytheon Trimodal Imager (TMI) uses coded aperture and Compton imaging technologies as well as the nonimaging shadow technology to locate an SNM or radiological threat in the presence of background. The coded aperture imaging is useful for locating and identifying radiological threats as these threats generally emit lower energy gammas whereas the Compton imaging is useful for SNM threats as in addition to low energy gammas which can be shielded, SNM threats emit higher energy gammas as well. The shadow imaging technology utilizes the structure of the instrument and its vehicle as shadow masks for the individual detectors which shadow changes as the vehicle moves through the environment. Before a radioactive source comes into the fields of view of the imagers it will appear as a shadow cast on the individual detectors themselves. This gives the operator advanced notice that the instrument is approaching something that is radiological and on which side of the vehicle it is located. The two nuclear images will be fused into a combined nuclear image along with isotope ID. This combined image will be further fused with a real-time image of the locale where the vehicle is passing. A satellite image of the locale will also be made available. This instrument is being developed for the Standoff Radiation Detection System (SORDS) program being conducted by Domestic Nuclear Detection Office (DNDO) of the Department of Homeland Security (DHS).© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.