Charles F. Coker

Fast line-of-sight imagery for target and exhaust-plume signatures (FLITES) scene generation program

The Fast Line-of-sight Imagery for Target and Exhaust Signatures (FLITES) is an advanced scene generation program capable of producing high-fidelity synthetic signatures for Infrared (IR) applications. The signature methodology provides physically traceable solutions to compute hardbody and plume radiation. An exact approach to render pixel-accurate scenes is provided to guarantee the pixel intensities are not aliased regardless of scene size, orientation, and range between the viewer and scene object. The FLITES program architecture has been developed to provide an Application Programming Interface (API) suitable to allow direct linking to higher-level simulations. This architecture also supports distributed processing to allow the program to be executed on processor clusters. The program is written in C++ and provisions have been included to allow the important signature routines such as bi-directional reflection and plume radiance transport to be replaced with alternate, application-specific, approaches if required. FLITES principle advancement has been in the area of plume signatures from three-dimensional (3D) plume flowfields. This capability allows complex flowfields to be rendered by FLITES that include helicopter plumes, staging transients, asymmetric turbulent flowfields, and exhaust plumes from airborne objects operating at an angle-of-attack relative to the ambient air stream.

Irma 5.2 multi-sensor signature prediction model

The Irma synthetic signature prediction code is being developed by the Munitions Directorate of the Air Force Research Laboratory (AFRL/MN) to facilitate the research and development of multi-sensor systems. There are over 130 users within the Department of Defense, NASA, Department of Transportation, academia, and industry. Irma began as a high-resolution, physics-based Infrared (IR) target and background signature model for tactical weapon applications and has grown to include: a laser (or active) channel (1990), improved scene generator to support correlated frame-to-frame imagery (1992), and passive IR/millimeter wave (MMW) channel for a co-registered active/passive IR/MMW model (1994). Irma version 5.0 was released in 2000 and encompassed several upgrades to both the physical models and software; host support was expanded to Windows, Linux, Solaris, and SGI Irix platforms. In 2005, version 5.1 was released after an extensive verification and validation of an upgraded and reengineered active channel. Since 2005, the reengineering effort has focused on the Irma passive channel. Field measurements for the validation effort include the unpolarized data collection. Irma 5.2 is scheduled for release in the summer of 2007. This paper will report the validation test results of the Irma passive models and discuss the new features in Irma 5.2.

Irma 5.1 multisensor signature prediction model

The Irma synthetic signature prediction code is being developed to facilitate the research and development of multisensor systems. Irma was one of the first high resolution Infrared (IR) target and background signature models to be developed for tactical weapon application. Originally developed in 1980 by the Munitions Directorate of the Air Force Research Laboratory (AFRL/MN), the Irma model was used exclusively to generate IR scenes. In 1988, a number of significant upgrades to Irma were initiated including the addition of a laser (or active) channel. This two-channel version was released to the user community in 1990. In 1992, an improved scene generator was incorporated into the Irma model, which supported correlated frame-to-frame imagery. A passive IR/millimeter wave (MMW) code was completed in 1994. This served as the cornerstone for the development of the co-registered active/passive IR/MMW model, Irma 4.0. In 2000, Irma version 5.0 was released which encompassed several upgrades to both the physical models and software. Circular polarization was added to the passive channel and the doppler capability was added to the active MMW channel. In 2002, the multibounce technique was added to the Irma passive channel. In the ladar channel, a user-friendly Ladar Sensor Assistant (LSA) was incorporated which provides capability and flexibility for sensor modeling. Irma 5.0 runs on several platforms including Windows, Linux, Solaris, and SGI Irix. Since 2000, additional capabilities and enhancements have been added to the ladar channel including polarization and speckle effect. Work is still ongoing to add time-jittering model to the ladar channel. A new user interface has been introduced to aid users in the mechanism of scene generation and running the Irma code. The user interface provides a canvas where a user can add and remove objects using mouse clicks to construct a scene. The scene can then be visualized to find the desired sensor position. The synthetic ladar signatures have been validated twice and underwent a third validation test near the end of 04. These capabilities will be integrated into the next release, Irma 5.1, scheduled for completion in the summer of FY05. Irma is currently being used to support a number of civilian and military applications. The Irma user base includes over 130 agencies within the Air Force, Army, Navy, DARPA, NASA, Department of Transportation, academia, and industry. The purpose of this paper is to report the progress of the Irma 5.1 development effort.

Closed-loop real-time infrared scene generator

A computer program has been developed to provide closed-loop infrared imagery of composite targets and backgrounds in real- time. This program operates on parametric databases generated off-line by computationally intensive first principle physics codes such as the Composite Hardbody and Missile Plume (CHAMP) program, Synthetic Scene Generation Model (SSGM), and Multi- Spectral Modeling and Analysis (MSMA/Irma program. The parametric databases allow dynamic variations in flight and engagement scenarios to be modeled as closed-loop guidance and control algorithms modify the operational dynamics. The program is tightly coupled with the parametric databases to produce infrared radiation results in real-time and OpenGL graphic libraries to interface with high performance graphic hardware. The program is being sponsored for development by the Kinetic Kill Vehicle Hardware-in-the-Loop Simulator facility of the Air Force Research Laboratory Munitions Directorate located at Eglin AFB, Florida.

Demonstration of innovative techniques used for real-time closed-loop infrared scene generation

Real-time infrared (IR) scene generation for Hardware-in-the- Loop (HWIL) testing of IR seeker systems is a complex operation. High frame rates and high image fidelity are required to properly evaluate a seeker systems designation, identification, tracking, and aim-point selection tasks. Rapidly improving Commercial-off-the-Shelf (COTS) scene generation hardware has become a viable solution for HWIL test activities conducted at the Kinetic Kill Vehicle Hardware-in- the-Loop Simulator (KHILS) facility at Eglin AFB, Florida. A real-time IR scene generation implementation for a complete closed-loop guided missile simulation test entry was accomplished at KHILS. The scenarios used for the simulation were Theater Missile Defense (TMD) exo-atmospheric hit-to-kill intercepts of a re-entry target. Innovative scene generation techniques were devised to resolve issues concerning scene content and rendering accuracy while maintaining the required imaging frame rate. This paper focuses on the real-time scene generation requirements, issues, and solutions used for KHILS test entries.

Rendering energy-conservative scenes in real time

Real-time infrared (IR) scene generation from HardWare-in- the-Loop (HWIL) testing of IR seeker systems is a complex problem due to the required frame rates and image fidelity. High frame rates are required for current generation seeker systems to perform designation, discrimination, identification, tracking, and aimpoint selection tasks. Computational requirements for IR signature phenomenology and sensor effects have been difficult to perform in real- time to support HWIL testing. Commercial scene generation hardware is rapidly improving and is becoming a viable solution for HWIL testing activities being conducted at the Kinetic Kill Vehicle Hardware-in-the-Loop Simulator facility at Eglin AFB, Florida. This paper presents computational techniques performed to overcome IR scene rendering errors incurred with commercially available hardware and software for real-time scene generation in support of HWIL testing. These techniques provide an acceptable solution to real-time IR scene generation that strikes a balance between physical accuracy and image framing rates. The results of these techniques are investigated as they pertain to rendering accuracy and speed for target objects which begin as a point source during acquisition and develop into an extended source representation during aimpoint selection.

High-fidelity phenomenology modeling of infrared emissions from missile and aircraft exhaust plumes

The generation of high-fidelity imagery of infrared radiation from missile and aircraft exhaust plumes is a CPU intensive task. These calculations must include details associated with the generation of the plume flowfield and transport of emitted, scattered, and absorbed radiation. Additionally, spatial and temporal features such as mach discs, intrinsic cores, and shear layers must be consistently resolved regardless of plume orientation to eliminate nonphysical artifacts. This paper presents computational techniques to compute plume infrared radiation imagery for high frame rate applications at the Kinetic Kill Vehicle Hardware-in-the-loop Simulator facility located at Eglin AFB. Details concerning the underlying phenomenologies are also presented to provide an understanding of the computational rationale. Finally, several example calculations are presented to illustrate the level of fidelity that can be achieved using these methods.

Real-time three-dimensional infrared scene generation utilizing commercially available hardware

Real-time infrared (IR) scene generation for HardWare-In- the-Loop (HWIL) testing is a complicated problem. As a consequence, real-time signal phenomenology and real-time sensor effects modeling have been difficult to accomplish. For example, modern systems are burdened with designation, discrimination, identification, tracking, and aimpoint selection tasks. This requires that sensor data rates increase and therefore faster computations for real-time scene generation systems are necessary in testing environments. Moreover, commercial scene generation hardware is rapidly improving making it a viable solution for HWIL applications in the Kinetic Kill Vehicle Hardware-in-the- Loop Simulator facility. This paper presents the primary analysis performed to determine the strengths and weaknesses of using commercially available hardware and software for real-time scene generation in support of HWIL testing. Finding the appropriate solution to real-time IR scene generation requires striking a balance between physical accuracy and image framing rates. This effort is to determine rendering accuracy and speed for target models which begin as a point source during acquisition and develop into an extended source representation during aimpoint selection.

Composite hardbody and missile plume (CHAMP 2001) IR scene generation program

The Composite Hardbody and Missile Plume (CHAMP) program is a computer simulation used to provide time dependent high- fidelity infrared (IR) simulations of airborne vehicles. CHAMP computational algorithms are based on first principle physics that compute hardbody and exhaust plume radiation (absorption, emission, and reflection) for arbitrary vehicle operational state, position, orientation and atmospheric condition. All computations are performed as a function of time to allow complex vehicle dynamics to be simulated. Image processing functions are included to generate anti-aliased focal plane imagery. CHAMP can be utilized to simulate post-boost vehicle, re-entry vehicle, boost missile, theater missile, cruise missile, aircraft, and helicopter applications. CHAMP development is sponsored by the Kinetic Kill Vehicle Hardware- In-the-Loop Simulator (KHILS) facility at Eglin AFB, Florida. CHAMP is routinely utilized by KHILS to support on-going hardware-in-the-loop testing of IR seekers. Many of these tests are complex and diversified. CHAMP has been structured to support these tests by employing current generation object oriented design methodologies that facilitate adaptation to specific test requirements.

Spatial and sampling analysis for a sensor viewing a pixelized projector

This paper presents an analysis of spatial blurring and sampling effects for a sensor viewing a pixelized scene projector. It addresses the ability of a projector to simulate an arbitrary continuous radiance scene using a field of discrete elements. The spatial fidelity of the projector as seen by an imaging sensor is shown to depend critically on the width of the sensor MTF or spatial response function, and the angular spacing between projector pixels. Quantitative results are presented based on a simulation that compares the output of a sensor viewing a reference scene to the output of the sensor viewing a projector display of the reference scene. Dependence on the blur of the sensor and projector, the scene content, and alignment both of features in the scene and sensor samples with the projector pixel locations are addressed. We attempt to determine the projector characteristics required to perform hardware-in-the-loop testing with adequate spatial realism to evaluate seeker functions like autonomous detection, measuring radiant intensities and angular positions or unresolved objects, or performing autonomous recognition and aimpoint selection for resolved objects.