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/infrared (EO/IR) sensors deployed in:
In particular, there is a need in U.S. missile defense for HWIL simulation of visible and infrared (IR) sensors for ballistic missile engagement.
Terrain and Cloud Scenes
GAIA™ (Global-scene Architecture for Integrated atmosphere, terrain, and cloud Analysis) is a physics-based model for accurately and rapidly generating terrain and cloud imagery in the UV, visible and IR for any location on Earth at any time of year. GAIA™ is database driven, incorporating a large amount of remotely-sensed and other measured data, such as terrain altitude, land cover, terrain material optical and thermal properties, satellite cloud imagery, and cloud products. This location and season based data is used to define the terrain and cloud structure for the user-defined scene. Atmospheric effects and radiance values to support scene simulation are provided by the AETHER™ radiative transfer model. GAIA™ can calculate at-aperture radiance for any reasonable sensor geometry, including space-based, airborne and ground-based systems. GAIA™ was funded by the Missile Defense Agency SBIR program in order to provide the defense community with the ability to characterize the background UV/VIS/IR radiation battle-space environment, and support the development of next generation ballistic missile warning, defense, and surveillance systems. The GAIA™ architecture was designed to allow efficient and consistent interface 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. The OCEANUS™ model has also been integrated into GAIA™ to provide enhanced ocean scene capabilities, for a scene-generation model that covers the earth.
OCEANUS™ (OCEAN Universal Scene) is a physics-based ocean background scene model developed by CPI with Missile Defense Agency SBIR funding 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. OCEANUS™, like GAIA™, is database driven, incorporating global, season-dependent remotely-sensed ocean data such as surface wind speed, salinity, chlorophyll concentration and sea surface temperature. OCEANUS™ can generate both static and time-dependent realistic ocean surfaces, which are used in the creation of high-fidelity ocean imagery in the UV, visible and IR spectral regions. The OCEANUS™ model is designed to incorporate all key ocean phenomena, including surface bidirectional reflectivity and directional emissivity from the ocean surface, multiple scattering within the ocean volume, and reflections from the ocean floor. Atmospheric effects and radiance values to support scene simulation are provided by the AETHER™ radiative transfer model. OCEANUS™ can accommodate any reasonable sensor geometry, including space-based, airborne and surface-based sensor systems. OCEANUS™ has been integrated into GAIA™ to provide a high-fidelity scene simulation capability that covers the earth.
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), now the Missile Defense Agency (MDA), starting in the late 1980s. CPI joined NRL's SSGM team in 1994 and has been involved in multiple aspects of the SSGM program, including user support and most recently the porting of SSGM from IRIX to Linux.
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 databases 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.
Although CPI currently has a contract to maintain SSGM, MDA no longer supports the program, and NRL has stopped distributing SSGM. The last version released by NRL was SSGM’08.1 in 2011.