Original Date: 05/01/2000
Revision Date: 01/18/2007
Best Practice : Infrared Countermeasures Simulation and Test
Heat seeking missiles are designed to track bright infrared (IR) aircraft sources such as engines and exhaust plumes. As the target maneuvers, the missile uses the changes in the timings of the detector modulation to track the target and determine course corrections. Infrared countermeasures (IRCM) systems, or jammers, broadcast an IR beam which is modulated with timing characteristics that are similar to those used by the missile. If successful, the jammer flashes will either cause the missile to severely alter its flight course (causing a miss) or seek a false target position (optical breaklock). In the past, Northrop Grumman Defensive Systems Division (DSD) performed IRCM simulations in an open-loop configuration with limited aircraft vulnerability and technique assessment capability. In addition, no measure of miss distance was possible with an open-loop test, which leads to over-design of the jammer source. Today, the company employs unique, multi-level simulation facilities to support IRCM development. These facilities ensure successful simulations and live-fire tests under customer scrutiny.
Northrop Grumman DSD’s approach has minimized the development cost and design-to-production schedule, while maximizing the cost-performance trade-off. The company uses a variety of hardware-in-the-loop simulation resources and digital simulation modeling tools for developing radio frequency (RF) and IRCM; refining waveform parameters; and evaluating effectiveness against threat systems. Many of these resources were built and are maintained by Northrop Grumman DSD specifically for these purposes. In addition, government furnished equipment and software legacy models are used to support the company’s initiatives and contracted program efforts.
The company developed and maintains four levels of IR missile simulation of increasing complexity and fidelity. These simulations involve the following test configurations: an open-loop rate table facility; an atmospheric optical path; an all digital-based, closed-loop simulation suite; and a full degree-of-freedom hardware closed-loop facility. Each is used at a different stage in the evolution of the IRCM design.
The open-loop simulation is used in the requirements definition phase, and the effects of the atmospheric transmission are determined with the aid of the rooftop testing facility. During the design phase, the all digital simulation capability is used to determine the subsystems sensitivity. The design optimization is accomplished with the aid of the close-loop simulation and then subjected to live-fire verification. These tools are continually upgraded and adapted by Northrop Grumman DSD as the latest threat information is obtained through traditional channels as well as unique testing opportunities.
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