|Acquisition Program: ||PEO Aviation|
| ||The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.|| Objective: ||Develop a prototype active terahertz (>100 GHz) imager that can render objects through brownout conditions up to 100 m away.
|| Description: ||Aids for navigating during brownout conditions  have generally used either RADAR or LADAR techniques.  Active RADAR techniques penetrate brownout well but render coarse images and are detectable by adversaries at great distances. Active LADAR renders much higher resolution images, but laser radiation is strongly scattered by brownout debris and can pose a safety hazard to ground personnel. Although terahertz signature science is still in its infancy,  THz imaging techniques may manifest many of the best attributes of both RADAR and LADAR by combining good penetration with good resolution without posing a radiation hazard. Often cited among its many limitations,  the fact that THz radiation is naturally absorbed by water vapor in the atmosphere affords the intriguing opportunity to limit its ultimate propagation range. Thus, by choosing the appropriate THz operational frequency, an active THz imager can penetrate brownout to detect nearby objects while remaining undetectably covert at greater distances.
In order to construct an active THz imager, appropriate THz transceiver and imaging technology must be developed. Although a broadband THz source and detector may be considered, preference is for a narrowband, tunable frequency heterodyne transceiver because of its superior signal to noise, spatial resolution, and tunable propagation range. Equally importantly, the technique for rendering an image (e.g. scanning mirror, phased array scanner, staring focal plane array) should be chosen to allow for rapid image refresh (>1 Hz) over a grid with sufficient resolution to image obstacles up to 100 m away. Since this prototype imager will be designed to assist navigation, it is only necessary that the imager face the direction of motion with a field of view comparable to the pilot's.
|| ||PHASE I: Design an active THz imager that can penetrate brownout conditions to image objects up to 100 m away. Detailed descriptions of the transceiver and imager design must quantitatively specify how the chosen technology solutions will perform (e.g. spatial resolution vs range, field of view, pixel signal-to-noise, image refresh rate) in realistic brownout navigation scenarios. The ability to chose the propagation range by adjusting the THz operational frequency must be included. From this design, develop a strategy to construct a laboratory-scale technology demonstrator that will allow AMRDEC to assess the performance of this potential navigation aid.
|| ||PHASE II: Construct and deliver to AMRDEC a laboratory-scale technology demonstrator of an active THz imager that can penetrate brownout conditions and detect obstacles covertly. The demonstrator must combine a transceiver and a image rendering system with sufficient resolution to image objects in brownout conditions up to 100 m away within a fixed field of view, preferably with an image refresh rate >1 Hz and an adjustable propagation range. Based on the lessons learned during the construction and initial testing of the demonstrator, deliver an improved design for a deployable active THz imager that can penetrate brownout conditions to render an image of objects up to 100 m away while remaining undetectable at an adjustably greater distance.
|| ||PHASE III: A navigation aid for pilots in brownout conditions is increasingly important to ongoing military operations not just in southwest Asia but around the world. This project will provide the means for critically assessing the potential of THz imaging against competing solutions. The insight and technology developed will directly support a number of current or planned navigation assistance acquisition programs. In addition, commercial pilots and both commercial and military drivers sometimes face similar brownout navigation challenges, so this project will naturally develop dual-use technology. Finally, a working THz imager will allow fundamental questions about THz signature science be addressed, potentially opening new commercial and military markets for THz techniques or closing inappropriate ones.
|| References: ||
 http://www.vtol.org/vertiflite/brownout.pdf, http://en.wikipedia.org/wiki/Brownout (aviation)
 http://www.navysbir.com/n08 2/N082-124.htm, http://www.navysbir.com/n08 2/N082-147.htm
 F.C. De Lucia, Proc. SPIE 6373, 637304 (2006); doi:10.1117/12.683848
 S.T. Fiorino et al., Proc. SPIE, Vol. 7324, 732410 (2009); doi:10.1117/12.818922
 M.J. Rosker and H.B. Wallace, Microwave Symposium 2007, IEEE/MTT-S International, p. 773 (2007). H.J. Liebe, International J. of Infrared and Milimeter Waves, Vol. 10, p. 631 (Springer, 1989).|
|Keywords: ||Bronwout, Navigation assist, Terahertz imaging, Covert active RADAR|
Questions and Answers:
Q: 1. Just to be clear - does the "m" in "100 m" refer to meters?
2. The 'range restriction with frequency' concept implies that there is a tradeoff between covert imaging and being able to see - is a system that utilizes minimum power to create a suitable image acceptable, even if it does not use "tuning" to frequencies absorbed by the atmostphere?
3. Is detection or exploitation that is a concern?
A: 1. Yes.
2. The drop in power with range varies dramatically with frequency in the THz region. The objective of this topic was to exploit this behavior to obtain high resolution imagery that penetrates brownout conditions without propagating long distances at which it might be detected. This is fundamentally different than taking an existing RADAR and turning down the power.
3. The objective is to develop an active imager that would not betray the long range covertness of the aircraft.
Q: Can we integrate a commercial THz source into the proposed imager system?
Or do we have to develop a new THz source to meet the topic requirement?
A: The emphasis of the topic is to develop a THz imager. Commercial components, including sources and detectors, may be used as necessary.
Q: Is there any preference for frequency band(s): e.g. 300 GHz versus 400 GHz versus 500 GHz?
A: No. The operational frequency band(s) will be determined by the performer during the phase I analysis that leads to the design of the imager to be constructed in phase II.
Q: Do you have a range and cross-range resolution goal or preference?
A: No. The operational range and cross-range resolution goals will be determined by the performer during the phase I analysis that leads to the design of the imager to be constructed in phase II. Note however that the solicitation requires objects be imaged out to 100 m with whatever resolution your imager can achieve (the higher, the better of course!).
Q: Do you have weight/volume targets for the first prototype and/or the eventual product?
A: No. The imager developed in Phase II will be a laboratory-scale demonstrator delivered to AMRDEC. It will not be mounted on a helicopter.
Q: What form of laboratory demonstrator is expected for delivery in Phase II?
Are you seeking a stand-alone packaged prototype, or can the demonstrator use commercially available (possibly rack mounted) hardware for certain sub-assemblies?
A: There are no constraints on the form of the laboratory demonstrator delivered, only that it work as proscribed in the Phase I analysis and design.
Q: Is it a long-term goal to have an image refresh rate of more than 10 Hz?
A: Certainly it is desirable to have an image refresh rate as fast as possible, but this too may be constrained during the trade-off analysis performed in phase I.
Q: Is it a long term goal to see a small target, e.g. a wire, or is the emphasis on dismounts?
A: No long term goal was specified. What is desired is to develop an imager that provides the best possible resolution traded off against constraints imposed by atmospheric propagation and technology. The higher the resolution the better, as long as it can see through brownout conditions and "see" objects up to 100 m away. The Phase I analysis and trade off study will identify the size of those objects that can be seen, and the Phase II hardware deliverable will demonstrate this capability.