Scene generation employs the use of a computer model to create a representation of a world as seen from a particular vantage point using phenomenology and physics. The scenes are created to achieve a useful representation of the domain of interest for a given application such as video games, simulation training for vehicle operators, models of human anatomy, or weapon system sensor components. For scientific and sensor applications, scene generation is usually associated with the synthetic modeling of the propagation of electromagnetic waves through a defined environment (e.g. atmosphere, ocean, or illumination of a terrain) in specific regions of the electromagnetic spectrum such as the Optical (visible, infrared, ultraviolet) or Radio Frequency. While most scene generators for military applications are designed to create scenes in the visible for applications such as flight training, driver simulations, and simulation of individual combatants, there is also a need for scene generation for design and hardware-in-the-loop (HWIL) testing of electro-optical/infra-red (EO/IR) sensors deployed in:
In particular, there is a need in U.S. missile defense for HWIL simulation of visible and infra-red (IR) sensors for ballistic missile engagement.
Targets in Flight
The Naval Research Laboratory's (NRL) Space Science Division in Washington, DC led the development of the Synthetic Scene Generation Model (SSGM) for the Strategic Defense Strategic Defense Initiative Office (SDIO) starting in the late 1980s. CPI joined NRL's SSGM team in 1994 and has played a leading role in designing and developing SSGM as part of the Battlespace Environment and Signatures Toolkit (BEST), an effort sponsored by the Missile Defense Agency (MDA).
SSGM is a high-fidelity physics-based model that is used to predict the ability of various electro-optical sensors and advanced surveillance systems to observe the spectral radiance emitted by targets in flight, such as ballistic missiles and their exhaust plumes, as well as the background spectral radiance from the surrounding atmospheric environment, from radio frequency (RF) to visible wavelengths. SSGM aids users in simulating a battlefield environment in which ballistic missiles are detected, acquired, tracked, and engaged. SSGM integrates data bases and validated phenomenology models into a common software framework to provide a traceable standard for generating complex optical signature information. This signature information is then used in the design, simulation, and tests of sensor and system performance. It is also used to perform R&D analyses, to support system acquisition, and to provide a common phenomenology basis for various studies associated with missile defense. SSGM is being incorporated as one component in BEST, a larger single software application that is designed to meet the broad needs of the missile defense community to include: analysts, force-on-force simulations, and HWIL facilities. CPI has had the responsibility for integrating SSGM into BEST, and currently provides support to the SSGM/ BEST programs in the areas of user support, systems requirements, analysis, and testing.
Terrain and Cloud Scenes
GAIATM is a robust computer code for simulating terrain and cloud imagery to characterize the background UV/VIS/IR radiation battlespace environment that supports development of next generation ballistic missile warning, defense, and surveillance systems. The rationale for GAIATM is to have a model and infrastructure that is designed to provide a collection of standard interfaces that efficiently and seamlessly unifies existing, improved, and/or new computer code in a consistent and fully integrated computer environment, and allows for the integration of satellite imagery and data products. GAIATM will possess an architecture that can be efficiently and consistently interfaced with existing computer modeling environments, such as the Fast Line-of-sight Imagery for Target and Exhaust-plume Signatures (FLITES) scene generation or SSGM codes. When complete, GAIATM will provide the missile defense community with the ability to generate high resolution, high fidelity scenes of the surface, and when combined with the OCEANUS model for ocean scenes, will provide a model that covers the earth.
Ocean and Cloud Scenes
OCEANUSTM is a physics-based ocean background scene model being developed by CPI to model the environmental radiance conditions required for the development of optimal sensors for detection and tracking of ballistic missiles and other targets of interest over ocean backgrounds. It provides ocean scenes of the environmental radiance conditions in the UV/VIS/IR through modeling and simulation for development of optimal sensors and detection approaches, that takes into account geometries that intercept earth ocean backgrounds and includes any intervening clouds. When completed, OCEANUSTM will possess a software architecture designed to efficiently and seamlessly unify existing, improved, and/or new computer code, along with access to satellite measurements of ocean parameters, in a consistent and fully integrated computer environment that can be utilized by state-of-the-art background radiation codes, such as the SAMM2 (SHARC and MODTRAN Merged 2), FLITES, and SSGM codes to meet missile warning/defense surveillance needs. OCEANUSTM is presently being developed under a MDA SBIR Phase II project. This ocean model when combined with GAIATM will provide a model that covers the earth.
Atmospheric Radiance and Transmittance
Dr. William M. Cornette, a principal scientist at CPI, conceived, developed, and continues to maintain and extend the Moderate Spectral Atmospheric Radiance and Transmittance (MOSART) code. It is a U.S. Department of Defense (DoD) standard code for predicting the radiative environment in the UV/VIS/IR/MMW to provide input for scene and signature simulations. MOSART provides atmospheric transmission along sensor-target line-of-sight paths, optical radiance backgrounds (e.g., terrain, clouds, limb, and space) against which targets are detected by sensor systems, and appropriate irradiances (e.g., solar, lunar, earthshine, skyshine). An extensive set of global databases is incorporated into the code, including climatologies, terrain elevation, water/snow compositions, ecosystem type, climatological atmospheric profiles, hydrology, soils, and land cover classes. The global database model allows a full four-dimensional representation of the earth’s atmosphere (i.e., altitude, latitude, longitude, and time) with radiative transfer varying as the line-of-sight moves within the spatially and temporally changing atmosphere. The MOSART code provides the path transmittance, path radiance, apparent solar and lunar irradiances, and the diffuse, multiple scattered irradiances on a three-dimensional spatial grid required to support scene generation software.
CPI is currently using MOSART (v3.0) as one of the components in the development of the GAIATM and OCEANUSTM scene generation models (see below) and the ISIS earthshine/skyshine model, which are being funded by MDA as Small Business Innovative Research (SBIR) projects. CPI provided the current released version of MOSART (version v2.0.4), which is available from NRL.