William T. Kersey

Classification of targets using optimized ISAR Euler imagery

Various approaches exist to enable target classification through a decomposition of the polarimetric scattering matrix. Specifically, the Euler decomposition attempts to express the target scattering properties through more physically relevant parameters. Target classification in general has been limited by signature variability and the saturation of images by non-persistent scatterers.1 The Euler decomposition is sensitive to additional parameter ambiguities.2 It will be demonstrated how undesirable ambiguities may be identified and mitigated. Through the analysis of polarimetric ISAR signatures obtained in compact radar ranges at the University of Massachusetts Lowell Submillimeter Technology Laboratory (STL)3,4,5,6 and the U.S. Army National Ground Intelligence Center (NGIC), the cause of non-persistent scatters will be investigated. A proper characterization of non-persistence should lead to better optimization of the Euler decomposition, and thus improve target classification.

Analysis of fully polarimetric W-band ISAR imagery on seven-scale model main battle tanks for use in target recognition

Fully polarimetric high-resolution W-band target signature data has been collected on 7 high fidelity 1/16th scale model main battle tanks. Data has been collected at several different elevation angles and target poses. Additionally, targets have been measured both on 1/16th scale simulated ground terrain and in free-space. ISAR images were formed from this data for use in several different target identification algorithms. These algorithms include using the data in both linear and circular polarization. The results of the inter-comparisons of the data using different algorithms are presented. Where possible the data has been compared with existing W-band Full-scale field measurements. The data is taken using a 1.55THz compact range designed to model W-band. The 1.55THz transceiver uses two high- stability optically pumped far-infrared lasers, microwave/laser Schottky diode side-band generation for frequency sweep, and a pair of Schottky diode receivers for coherent integration.

Exploitation of ISAR imagery in Euler parameter space

Efforts are being made to exploit the full-polarimetric radar scattering nature of ground targets to extract maximum information, enabling target identification and classification. These efforts have taken varied approaches to decomposing the polarimetric scattering matrix into more meaningful, phenomenological parameter spaces. The Euler parameters have potential value in target classification but have historically met with limited success due to ambiguities that arise in the decomposition as well as the parameters sensitivity to noise and target movement. Using polarimetric ISAR signatures obtained from stationary targets in compact radar ranges at the University of Massachusetts Lowell Submillimeter Technology Laboratory (STL)1,2,3,4 and the U.S. Army National Ground Intelligence Center (NGIC), correlation studies were performed in the Euler parameter space to assess to its impact on improving target classification. Methods for deriving explicit transform equations that minimize ambiguities will be presented, as well as the results of the correlation studies.

A signature correlation study of ground target VHF/UHF ISAR imagery

VV and HH-polarized radar signatures of several ground targets were acquired in the VHF/UHF band (171-342 MHz) by using 1/35th scale models and an indoor radar range operating from 6 to 12 GHz. Data were processed into medianized radar cross sections as well as focused, ISAR imagery. Measurement validation was confirmed by comparing the radar cross section of a test object with a method of moments radar cross section prediction code. The signatures of several vehicles from three vehicle classes (tanks, trunks, and TELs) were measured and a signature cross-correlation study was performed. The VHF/UHF band is currently being exploited for its foliage penetration ability, however, the coarse image resolution which results from the relatively long radar wavelengths suggests a more challenging target recognition problem. One of the studys goals was to determine the amount of unique signature content in VHF/UHF ISAR imagery of military ground vehicles. Open-field signatures are compared with each other as well as with simplified shapes of similar size. Signatures were also acquired on one vehicle in a variety of configurations to determine the impact of monitor target variations on the signature content at these frequencies.

Multiple-resolution study of Ka-band HRR polarimetric signature data

SAR resolution and polarization performance studies for ATR algorithms have been the source of recent attention. Thorough investigations are often hindered by the lack of rigorously consistent high-resolution full-polarimetric signature data for a sufficient number of targets across requisite viewing angles, articulations and environmental conditions. While some evaluative performance studies of high-value structures and conceptual radar systems may be effectively studied with limited field radar data, to minimize signature acquisition costs, pose-independent studies of ATR algorithm are best served by signature libraries fashioned to encompass the complexity of the collection scenario. In response to the above requirements, the U.S. Armys National Ground Intelligence Center and Targets Management Office originated, sponsored, and directed a signature project plan to acquire multiple target signature data at Eglin, AFB using a high resolution full-polarimetric Ka-band radar. TMO and NGIC have sponsored researchers at both the Submillimeter-Wave Technology Laboratory and Simulation Technologies to analyze the trade-off between signature resolution and polarimetric features (ongoing research) of this turntable data. The signature data was acquired at five elevations spanning 5 degree to 60 degree for a T-72M1, T-72B, M1, M60-A3 and one classified vehicle. Using signal processing software established in an NGIC/STL-based signature study, researchers executed an HRR and ISAR cross-correlation study involving multiple resolutions to evaluate peak performance levels and to effectively understand signature requirements through the variability of multiple target RCS characteristics. The signature-to-signature variability quantified on the four unclassified MBTs is presented in this report, along with a description and examples of the signature analysis techniques exploited. This signature data is available from NGIC/TMO on request for Government Agencies and Government Contractors with an established need-to-know.

Target variability and exact signature reproduction requirements for Ka-band radar data

A variety of ATR algorithms have promise improved performance, not yet realized operationally. Typically, good results have been reported on data sets of limited size that have been tested in a laboratory environment, only to see the performance degrade when stressed with real-world target and environmental variability. To investigate exact signature reproduction requirements along with target and environment variability issues for stressing new ATR metrics, the U.S. Armys National Ground Intelligence Center (NGIC) and Targets Management Office (TMO) originated, sponsored, and directed a signature project plan to acquire multiple target full-polarimetric Ka-band radar signature data at Eglin AFB, as well as its submillimeter-wave compact radar range equivalent using high-fidelity exact 1/16th scale replicas fabricated by the ERADS program. To effectively understand signature reproduction requirements through the variability of multiple target RCS characteristics, TMO and NGIC sponsored researchers at U Mass Lowells Submillimeter-Wave Technology Laboratory (STL) and Simulation Technologies (SimTech) to analyze the intra- class and inter-class variability of the full scale Ka-band turntable signature data. NGIC, TMO, STL and SimTech researchers then traveled to the location of the vehicles measured at Eglin AFB and conducted extensive documentation and mensuration on these vehicles. Using this information, ERADS built high fidelity, articulatable exact replicas for measurement in the NGICs compact radar ranges. Signal processing software established by STL researchers in an NGIC directed signature study was used to execute an HRR and ISAR cross-correlation study of the field and scale-model signature data. The signature to signature variability quantified is presented, along with a description and examples of the signature analysis techniques exploited. This signature data is available from NGIC on request for Government Agencies and Government Contractors with an established need-to-know.

X-band radar signature characteristics for main battle tanks in operational environments

An analysis of target separability has been performed under an OSD Target Management Initiative program entitled Radar Variations. The program has concentrated on analyzing radar signatures from multiple main battle tanks (MBTs) in order to quantify the differences in Ka-band signatures of vehicles due to intraclass and interclass target variations. As a significant factor in the success of the Radar Variations program, U Mass Lowells Submillimeter-Wave Technology Laboratory (STL) and U.S. Army National Ground Intelligence Center (NGIC) fabricated 1/16th scale exact replicas of the vehicles used in the Ka-band radar signature acquisition study directed by Simulation Technologies, Inc. (SimTech) and Targets Management Office (TMO). These replicas enabled NGIC to measure statistically significant amounts of high-fidelity signature data for a variety of target configurations with an indoor compact radar range.

Variability study of Ka-band HRR polarimetric signatures on 11 T-72 tanks

In an effort to effectively understand signature verification requirements through the variability of a structures RCS characteristics, the U.S. Army National Ground Intelligence Center (NGIC), with technical support from STL, originated a signature project plan to obtain MMW signatures from multiple similar tanks. In implementing this plan NGIC/STL directed and sponsored turntable measurements performed by the U.S. Army Research Laboratory Sensors and Electromagnetic Resource Directorate on eleven T-72 tanks using an HRR full-polarimetric Ka-band radar. The physical condition and configuration of these vehicles were documented by careful inspection and then photographed during the acquisition sequence at 45 degree(s) azimuth intervals. The turntable signature of one vehicle was acquired eight times over the three day signatures acquisition period for establishing measurement variability on any single target. At several intervals between target measurements, the turntable signature of a 30 m2 trihedral was also acquired as a calibration reference for the signature library. Through an RCS goodness-of-fit correlation and ISAR comparison study, the signature-to-signature variability was evaluated for the eighteen HRR turntable measurements of the T-72 tanks. This signature data is available from NGIC on request for Government Agencies and Government Contractors with an established need-to-know.