Francis J. Corbett

Problem set guidelines to facilitate ATR research, development, and performance assessments

In November of 2000, the Deputy Under Secretary of Defense for Science and Technology Sensor Systems (DUSD (S&T/SS)) chartered the ATR Working Group (ATRWG) to develop guidelines for sanctioned Problem Sets. Such Problem Sets are intended for development and test of ATR algorithms and contain comprehensive documentation of the data in them. A problem set provides a consistent basis to examine ATR performance and growth. Problem Sets will, in general, serve multiple purposes. First, they will enable informed decisions by government agencies sponsoring ATR development and transition. Problem Sets standardize the testing and evaluation process, resulting in consistent assessment of ATR performance. Second, they will measure and guide ATR development progress within this standardized framework. Finally, they quantify the state of the art for the community. Problem Sets provide clearly defined operating condition coverage. This encourages ATR developers to consider these critical challenges and allows evaluators to assess over them. Thus the widely distributed development and self-test portions, along with a disciplined methodology documented within the Problem Set, permit ATR developers to address critical issues and describe their accomplishments, while the sequestered portion permits government assessment of state-of-the-art and of transition readiness. This paper discusses the elements of an ATR problem set as a package of data and information that presents a standardized ATR challenge relevant to one or more scenarios. The package includes training and test data containing targets and clutter, truth information, required experiments, and a standardized analytical methodology to assess performance.

Use of laser radar for small space object experiments

This report briefly reviews the development, capabilities, and current status of pulsed high-power coherent CO2 laser radar systems at the Maui Space Surveillance System (MSSS), HI, for acquisition, tracking, and sizing of orbiting objects. There are two HICLASS systems, one integrated to the 0.6 m Laser Beam Director and one just integrated Summer 2000 to the 3.7 m Advanced E-O System (AEOS). This new system takes full advantage of the large AEOS aperture to substantially improve the ladar range and sensitivity. These improvements make the AEOS HICLASS system potentially suitable for tracking and characterization experiments of small < 30 cm objects in low-earth-orbits.

Real-time image generation with a pulsed coherent laser radar

A kilowatt class, pulsed CO2 laser radar has been developed at Textron under a joint US Army-Air Force program. It is currently undergoing field trials; and successful coherent imaging and tracking experiments have been conducted over the past two years at the Air Force Maui Space surveillance Site. This paper describes the receiver- processor architecture of the laser radar system, the algorithms and waveforms, and the output products which are high resolution range-Doppler and range-amplitude image. Attention will be paid to the hardware and software methods used to achieve real-time, wideband operations.

Acquisition, tracking, and sizing of small space objects

High-powered, pulsed CO2 coherent ladar systems and their potential application to space debris tracking and characterization.

Field ladar demonstration (FLD) system, algorithms, and Phase I/Phase II test results

The High Performance CO2 Ladar Surveillance Sensor system (HI-CLASS) is a state-of-the-art coherent ladar system which will provide precision tracking and high resolution imaging at the Air Force Maui Optical Station (AMOS). System development is occurring in 3 phases representing increasing hardware/software complexity and system capability. The recently-completed Phase I HI-CLASS system employs a compact, pulsed, coherent CO2 oscillator, a heterodyne receiver, and signal recorder coupled to the AMOS 0.6 m Laser Beam Director to demonstrate target (satellite) acquisition and tracking, illumination, return signal detection, signal recording, and off-line processing for range and range rate extraction and range- amplitude imaging. A description of the Phase I satellite ranging and ground-based remote sensing tests verifying the FLD system operating concept will be presented. The cooperative target range and range rate measurements, as well as imaging precursor demonstration, will be discussed. The talk will include a discussion of the 21 km demonstration of remote sensing using natural terrain returns. Results generated on phase I data with the phase II algorithm will also be described.

Theoretical and Monte Carlo analyses of the range-Doppler imaging capabilities of mode-locked CO2 ladars

Mode-locked CO2 lasers have been developed which can produce long coherent pulse trains consisting of many narrow subpulses. This laser waveform may be used to numerically generate range-Doppler images (inverse synthetic aperture radar images) of a target wherein the Doppler spread of a spinning target is used to create a synthetic cross-range target dimension. The narrow micro-pulse temporal width provides good range resolution, and the long coherent pulse train provides good frequency resolution of the (cross-range) target Doppler spread. In this paper we examine the algorithms and imaging capabilities of this waveform as implemented for the FLD and Hi-CLASS laser radar (ladar) systems which are now being installed in the AMOS facility on Mt. Haleakala, Maui and in an aircraft testbed.

Status report of an airborne CO2 transceiver for remote sensing employing direct and coherent detection

A multi-joule, wavelength agile, CO2 transceiver is being assembled in support of a two phase, airborne chemical sensing demonstration employing both direct (Phase I) and coherent (Phase II) detection methods. The Phase II, coherent detection transceiver concept design, and performance are described below.

Design considerations for a multichannel laser radar receiver/processor

HI-CLASS (FLD) Laser Radar Produces 2D range-Doppler images, range-amplitude images, azimuth and elevation offsets and whole body range and Doppler estimates of rapidly moving space based targets. The Receiver-Processor converts the return signature on two selectable waveforms into a heterodyned signal which is subjected to conditioning and normalization in the receiver (e.g., extraction of gross Doppler) and then operated on within the processor, primarily convolution and Fourier transformation, to produce the output products in real time at the operators workstation. This paper will show the instrument design, and provide a look at some of the parametric trade-offs considered in arriving at the final operating configuration. Details of the hardware, and software architectures will be presented, and the algorithms required for acquisition, tracking, and imaging will be explained.

Extending spectral coverage of gas lasers using EO and AO modulators: spectral purity issues

Both EO and AO modulators can be used to extend the spectral coverage of CO2 lasers in the 9 - 11 micrometers region. For laser radar local oscillator application, the spectral purity of the frequency shifter output must be high and can be achieved with an AO frequency shifter using a special modulator configuration and a molecular absorption technique. A 500 MHz AO frequency shifter was designed, tested and shown to have a high spectral purity at an output power level of over 50 mW with a conversion efficiency of a few percent.

Multispectral (IR and MMW) processing for automatic target detection

Automatic Target Recognition algorithms have been developed with limited success over the last few years. The processing to extract military targets from background clutter has difficulty under noisy, real-world conditions. Fusion of data from different wavelength sensors has been one approach to improve performance. The underlying theory is that signature data from different areas of the electro-magnetic spectrum will be complementary and clutter is frequency dependent. Recent work based on both statistical classification, and feature analysis in the thermal infrared and millimeter wave spectra, has shown interesting trends. We will provide a description of the IR/MMW target classification algorithms, the fusion architecture we employed, and processes used to search for the optimum features. Two distinct search and detect schemes were tested with different results. Data acquisition and reduction issues which affect algorithm experiments will also be discussed. A software based algorithm development test-bed was built at Textron to implement the multispectral targeting experiments. The effect of a modular, programmable test-bed on such experiments is to increase productivity and allow multivariate evaluatio ns.