The U.S. Air Force depends on new, advanced engines that are rigorously ground tested before first flight. Of great concern is that fighter aircraft engines operating with afterburners can experience combustion instabilities, called rumble and screech, that can significantly damage both the engine and the aircraft. Traditionally, bore-holes are cut in the afterburner case to mount dynamic pressure sensors to monitor for the onset of rumble and screech. In addition to high failure rates in this extreme environment, placing these sensors is very costly, and cutting bore-holes in engines is unpopular with engine manufacturers. For these reasons, scientists at Advanced Fuel Research, Inc., East Hartford, Conn., jointly with AEDC Air Force SBIR Program and the Aerospace Testing Alliance, both of Arnold Air Force Base, Tenn., have developed the Rumble and Screech Spatial Mapping Analyzer Tool (RASSMAT). RASSMAT is a non-contact, passive optical method for sensing and measuring rumble and screech. The positioning of its multiple optical heads provides for 2-D mapping of local oscillations in the cross-sectional area of the afterburner exhaust plane, which is important for localizing the source of instability to individual fuel-injectors in the afterburner.