TECHNOLOGY AREAS: Sensors

OBJECTIVE: This effort will develop a tactical threat warning sensor utilizing a common sensing aperture and receiver covering a broad range of the electromagnetic spectrum (EMS) encompassing both the optical and the radio frequency domains. This sensor will be capable of detecting military threats with emissions in the common radar bands (RF, 1-20 gigahertz frequency), the millimeter wave band (mmW, 20-300 gigahertz frequency), and optical bands including the ultraviolet (UV, 100-400 nanometer wavelength), visible (Vis, 400-700 nanometer wavelength), near infrared (NIR, 700-2000 nanometer wavelength), mid-wave infrared (MWIR, 2.0-5.5 micron wavelength), and long-wave infrared (LWIR, 8.0-12.0 micron wavelength). The sensor must be able to achieve background-limited performance (BLIP) for detection, identification, and determination of angle-of-arrival (AoA) of such diverse threats as radars used for target detection and missile guidance (RF and mmW), radio-frequency weapons (RF and mmW), missile exhaust plumes (UV, MWIR), hostile ground fire (UV, Vis, NIR, MWIR), lasers used for target designation and missile guidance (pulsed NIR, MWIR, LWIR), lasers used to disrupt optical systems (pulsed and continuous Vis, NIR, MWIR, LWIR), and laser weapons (pulsed and continuous Vis, NIR, MWIR, LWIR). Key innovations required for the envisioned system are apertures, detection methods, and receiver architectures that span the EMS while minimizing sensing elements and redundant processors, as well as reducing system requirements for size, weight, and available power (SWAP). An affordable and robust Common Optical / Radio-frequency Threat Sensor (CORTS) system will enhance the situational awareness of warfighters under hostile fire and improve the survivability of Navy vessels; Marine Corps and Army ground vehicles; and Navy, Marine Corps, Army, and Air Force aircraft.

DESCRIPTION: Threat warning is key to increasing the survivability of military platforms. Modern missiles and other rocket-propelled threats utilize a variety of guidance modes using both passive and active seekers operating in multiple bands of the electromagnetic spectrum. The increasing complexity and compactness of these guidance systems allow modern missiles to operate in multiple-modes, either sequentially or simultaneously, which necessitates tactical threat warning systems to operate over greater spectral (wavelength) and temporal (frequency) ranges to provide truly comprehensive situational awareness.

Simultaneous detection and identification of optical and radio-frequency threats, as well as determination of the direction of the threats to an accuracy of better than 5-degrees over a conical field of regard of at least 120-degrees, will provide significantly enhanced threat warning over current sensors that operate over a limited portion of the full EMS. All threat detections and required processing (threat declaration, ID, azimuth, and elevation) should be performed in real-time to enable cueing of external counterfire or countermeasures systems. (The specifics of these external systems are not germane to this topic, except that the sensor processing system should include the ability to generate a generic cueing signal or "trigger pulse" that can be synchronized with the time of detection to an accuracy of 10 milliseconds or better.) To facilitate tactical implementation, design considerations should include techniques to detect threats in the presence of background clutter and solar radiation; minimizing false alarms; decreasing size, weight, and exposed cross-section; and enhancing robustness against vibration, shock, and thermal variations.

PHASE I: Perform concept studies and preliminary design of the Common Optical / Radio-frequency Threat Sensor (CORTS). Explain the technical basis of the proposed broad spectrum sensing technology and the plan for maturing this technology in subsequent phases of this effort, with particular attention to assessing development risk and possible means of risk mitigation. Determine predicted performance against typical target tracking and guidance radars, missile exhaust plumes, and pulsed and continuous laser sources. Show that the sensor can be designed for operation on military tactical (jet) and assault (rotor wing) aircraft.

PHASE II: Perform detailed design of the Common Optical / Radio-frequency Threat Sensor (CORTS), including optical, mechanical, electronic and software components. Generate detailed drawings and bills of material for easy transition to Phase III production. Provide to the Navy a working prototype of the sensor and evaluate its operation against available threat hardware and simulators.

PHASE III: Perform modification of the Phase II prototype sensor for inclusion in a specific military vehicle. Work closely with a military sponsor to militarize the sensor and to provide appropriate outputs for integration into the vehicle. Modify the Phase II system design to conform to the military vehicle installation constraints.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: With the proliferation of shoulder-fired missiles, terrorist threats to commercial transportation, whether via ships, vehicles, or aircraft, have become a real concern. Development of this low-cost 360-degree field of view threat warning sensor will provide a means for Homeland Defense agencies to protect commercial transportation systems without an undue cost burden.

In addition to the threat detection application of this technology, the development of low-cost, real-time sensors with broad spectral coverage has a number of uses for machine vision and automated inspection applications. By coupling the sensor with a variety of electro-optical illuminators and RF emitters, the system could be readily adapted to surface and bulk quality inspection by identifying surface contaminants or sub-surface inclusions prior to material processing.

Examples of this application and the industries affected include:
� Airline manufactures currently have no easy reliable method to verify surface cleanliness prior to painting or sub-surface inclusions or voids that can lead to material fatigue. This technology would allow high-speed inspection of entire airframes or bulk components for surface or sub-surface irregularities that would reduce component lifetimes.
� Anti corrosion conversion coatings for maritime use require testing in salt-spray chambers to verify correct application and performance. Currently the industry has no way to quickly verify coating performance, nor inspect for inclusions of dissimilar materials that can act as corrosion sites. Adaptation of a common optical and radio-frequency sensor to determine any irregularities in the optical or RF characteristics of manufactured materials would provide manufactures a method to reduce corrosion inspection times from hours to seconds, quickly revealing areas of coating breach or material inclusions that would otherwise be invisible to the eye. This improvement in inspection capability would result in decreased manufacturing costs, increased profitability and reliability, and increased component lifetime for both the military and commercial users of these items.

REFERENCES:
1. David Adamy, "EW 101 - A First Course in Electronic Warfare", Artech House, Massachusetts (2001)

2. David Adamy, "EW 102 - A Second Course in Electronic Warfare", Artech House, Massachusetts (2004)

3. Joseph S. Accetta, David L. Shumaker, "The Infrared and Electro-Optical Systems Handbook", SPIE Optical Engineering Press, Washington (1993)

KEYWORDS: electronic warfare; threat warning; situtational awareness; radio frequency; millimeter wave; electro-optical