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of operation, such as inverse SAR (ISAR) image generation of ships at sea, may be employed with good
results. Combined with conformal antennas, large AESA-based SAR systems may be able to achieve
greater imaging and MTI capabilities as well as more specialized missions, such as single pass
interferometric SAR.
At the opposite end of the spectrum, vendors are taking advantage of the decreasing cost of radio
frequency (RF) technologies applicable to radar systems (driven primarily by the telecommunications
industry), to develop versions of sensors for tactical and lower payload class aircraft. For example, the
MISAR system is capable of imaging truck-sized targets at approximately 3.5 km slant range, from a
tactical class platform, even though the sensor is in the 10-pound weight class. While MISAR currently
does not form images on-board, there is fundamentally no reason this capability could not be integrated
within a reasonable weight margin, permitting consumers of the raw data to tap the unformed image
information from the raw feed, while tactical users could received a formed image – both from the same
platform.
UHF/VHF Foliage Penetration (FOPEN) SAR. In FY-97 DARPA, the Army and the Air Force began a
program that designed, fabricated and demonstrated a dual-band VHF/UHF radar with real-time onboard
image formation processing. The VHF/UHF SAR hardware is currently being flown on an Army-owned
RC-12 aircraft. The system was developed to target multiple platforms with little modification; one such
system is the Global Hawk UA. The sensor development program ended in 2003. In FY03, DARPA
began the Wide-Area All-Terrain Change Indication and Tomography (WATCH-IT) program to enhance,
UAS ROADMAP 2005
APPENDIX B – SENSORS
Page B-5
mature, and integrate exploitation technologies. The WATCH-IT program developed robust low false
alarm density change detection software to detect vehicles and smaller targets under foliage, under
camouflage and in urban clutter, and developed tomographic (3D) imaging to detect and identify targets
that have not relocated. DARPA demonstrated the capability of VHF/UHF SAR for building penetration,
urban mapping and performing change detection of objects inside buildings. Terrain characterization
technologies were also developed, including the abilities to rapidly generate bald-earth terrain height
estimates and to classify terrain features from multipass VHF/UHF SAR imagery. In September 2004,
DARPA demonstrated real-time onboard change detection (vehicles and IEDs) and rapid ground-station
tomographic processing, as well as rapid generation of bald earth digital elevation models (DEMs) using
stereo processing. In parallel, the Air Force Targets Under Trees (TUT) program enhanced the VHF SAR
by adding a 10-km swath width VHF-only mode, developing a real-time VHF change detection capability
and integrating FOPEN products into the targeting chain. In the summer of 2004, the VHF/UHF SAR
participated in the Combined Joint Task Force Exercise (CJTFEX-04) and the Joint Expeditionary Forces
Experiment (JEFX04). The system demonstrated real-time VHF-change detection and validated the
ability of VHF/UHF SAR to operate with other sensors. TUT provided real-time VHF change detection
cues to the Combined Air Operations Center (CAOC) and successfully tasked another sensor in real time
(a Predator surrogate with an EO/IR package) to prosecute mobile relocatable targets.
Light Detection and Ranging (LIDAR) FOPEN. Also known as LADAR (Laser Detection and Ranging).
Use of LIDAR is another method that offers the possibility of imaging through forest canopy. In current
and projected tests, an imaging LIDAR sensor on an aircraft takes several fore-and-aft cuts at a given area
of interest as the aircraft moves, allowing the sensor to “integrate” an image over time. Initial coverage
rates are far less than typical SAR or EO capabilities, but planned systems at this point are for
demonstration purposes only.
LIDAR imaging. LIDAR may be used to image through an obscuration as well. By using a precision
short laser pulse and capturing only the first photons to return, a LIDAR image can be formed despite the
presence of light-to-moderate cloud cover, dust, or haze. LIDAR can be used to simultaneously image
through cloud and foliage. LIDAR also provides the capability of rapidly producing high resolution
terrain elevation and mapping information as demonstrated by systems in the Urban Recon ACTD, with
elevation accuracies measured in single digit centimeters for relative accuracy and tens of centimeters for
absolute elevation accuracy. This type of information is particularly useful in urban operations.
LIDAR aerosol illumination. The task of detecting and identifying chemical or biological agents can be
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unmanned aircraft systems roadmap(58)
