Abstract: Defence Research and Development Canada—Atlantic conducted co-operative infrared (IR) surveillance of research vessel Quest from the air in October 2006 near Halifax harbour. A Canadian Forces Military Patrol Aircraft imaged the Quest in the mid-wave IR band using the Wescam MX-20 IR camera. The Quest cruised along headings such that the sun's azimuthal position was directly astern, perpendicular, and at 45 degrees to the ship heading. For each of the ship-sun orientations, the aircraft executed a flight pattern that consisted of starboard and port passes that transected the Quest at nominal altitudes of 30 m and 300 m. An additional pass along the ship heading from stern to bow was made at an altitude of 150 m. Wide field-of-view IR images were collected from ranges typically exceeding 5 km with a 640x512 pixel resolution. From the digital video, we have extracted the background radiance and the total contrast signature of the Quest for the various ship-sun-pass configurations. The background sky-to-sea profiles reveal a strong increase in mid-wave IR sea radiance with steepening viewing angle. The total contrast mid-wave IR signature has an approximate power-law decay with distance for ranges between about 1–10 km. At close ranges, we qualitatively note contributions to the signature by the radiance from the wake and from reflections of the ship in the sea surface.