Infrared Light Image
A multi-path, broadband infrared light source (foreground) and hyperspectral infrared imager are set up opposite each other with a towed airborne plume simulator burner installed in the High-Speed Fan Facility shooting a blast of fire and smoke between them. (U.S. Air Force photo by Jill Pickett)

The Advanced Missile Signature Center of the 718th Test Squadron, 804th Test Group, Arnold Engineering Development Complex (AEDC), has been helping the Department of Defense characterize the signatures of missile plumes for decades. Recently, a new measurement system was tested at Arnold Air Force Base, headquarters of AEDC, to help expand the capabilities of the Joint Standard Instrumentation Suite (JSIS) used by AMSC in collaboration with the Center for Countermeasures (CCM).

Through the Small Business Innovation Research Program, Physical Sciences Inc., or PSI, was awarded a contract to develop, build, and deliver a missile plume transmittance (MPT) measurement system at technology readiness level 6, meaning a prototype system that has been tested in the intended environment and performed close to or as expected.

In May, PSI and AEDC team members put the MPT measurement system consisting of two multi-path, broadband infrared light sources and two hyperspectral infrared imagers to the test at the High-Speed Fan Facility (HSFF). The HSFF, looking like a massively oversized floor blower fan, serves to blow air past a towed airborne plume simulator (TAPS) burner to simulate the air flow conditions when it is being towed by an aircraft. TAPS is a system that is used to closely simulate missile plumes through the use of a pyrophoric liquid, or one that burns on contact with air.

“By using different mixtures of pyrophoric liquids, and by varying the flow rate, TAPS can emulate a range of missile sizes and propellants,” said Dr. Robert Hiers, a scientist with AEDC. “TAPS provided a very convenient capability to test all the measurement features of the MPT.”

The MPT measurement system projects a high-intensity infrared light through a missile plume at two different angles. Two hyperspectral imagers are set up opposite the infrared light sources to collect images of the plume. The transmittance, or opacity of the plume, is calculated by comparing images of the plume with the light source off and on.

“Plume transmittance is an important quantity to understand for missile detection and tracking,” Hiers said. “Missile warning algorithms must detect and track the plume in the presence of cluttered backgrounds, sometimes with other bright sources in the field of view. It is important to understand how much of the background can be seen through the plume.”

The AEDC team executed more than 50 firings of the TAPS burner at the HSFF over two days to test the MPT measurement system.

“Several minor improvements were identified that will be accomplished prior to delivery of the final system to AEDC later this year,” Hiers said. “Then the system will be integrated into JSIS for deployment to future static firings of surface-to-air missile motors. The MPT measurement system will provide one more method for AEDC to apply in support of the test and evaluation of missile warning systems.”

JSIS is a joint effort of AEDC and the CCM. The suite has radiometric and other instrumentation for the characterization of plumes, trajectories, and attitude in flight of missiles, but can also be used to collect data during static motor firings, which is how the MPT measurement system is used. The data collected on threat missile signatures at live and static fire test events worldwide by the AMSC Field Measurement Team using JSIS is utilized by the AMSC Modeling and Simulation Team to develop computer models of plume signatures under all anticipated flight conditions.