Canadian Forces Auxiliary Vessel CFAV Quest was imaged in the long-wave infrared IR band during DRDC Atlantic sea trial Q280 in February 2004. From images collected over several days, we have extracted the ship, sea and sky radiances. A contrast radiance between the ship and the background was calculated to determine the long-wave IR signature. Our analysis shows that the daytime signature of the vessel is larger than at night in the long-wave IR band. The contrast radiance of the stack exceeds that from the hull when contrasted against the winter sea. And finally, by comparing with prior studies, we note that the contrast ratio is larger in the mid-wave IR than in the long-wave IR when the contrast is constrained to the ship stack. We used Ship IR to model the Quest and its maritime environment. We found that the results were in general agreement with the measured data for both the sea and sky background and the ship surface. Overall, the typical difference between measured and modeled results was about 1030 .