Ocean Universal Scene (OCEANUS™) Model
OCEANUS™ is a physics-based ocean background scene model that calculates water-leaving radiance in the ultraviolet (US), visible (VIS) and infrared (IR) portions of the spectrum (0.2 – 50 microns). The development of OCEANUS™ was funded by the Missile Defense Agency (MDA) SBIR program in order to create a model that generates scene signatures of the environmental radiance conditions in the UV/VIS/IR for the development of optimal sensors for detection and tracking of ballistic missiles and other targets of interest over ocean backgrounds. OCEANUS™ can simulate high-fidelity ocean imagery with spatial resolutions as fine as 1 mm for any reasonable sensor geometry, including space-based, airborne and ground-based systems.
OCEANUS™ is database driven, incorporating a large amount of remotely-sensed measured data. The data available includes monthly variations in the global sea surface temperature, the global sea surface salinity, the global sea ice, phytoplankton, CDOM, and suspended sediment distributions, global sea surface wind speed and direction, and ocean depth. This data characterizes the ocean spatially on a global scale for annual and multi-year cycles for local meteorological conditions, and accounts for the different ocean environments (e.g., open ocean, littoral, river mouths, estuaries). However, if desired the user can override these database values with customized inputs for a known ocean location.
OCEANUS™ 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 (important for visible wavelengths in the littoral zone). Both static and time-dependent ocean surface wave structure can be calculated based on local conditions such as surface wind speed and ocean depth. This pixel dependent surface orientation is important for calculating the bidirectional reflectivity and directional emissivity. Atmospheric effects and radiance values to support scene simulation are provided by the AETHER™ radiative transfer model. This includes atmospheric transmission, path radiance, incident direct diffuse solar irradiance, incident direct and diffuse lunar irradiance, and incident diffuse thermal irradiance, all on a three-dimensional grid (latitude, longitude and altitude).
Shown below is an animation of a sample wave structure for a wind speed of 12 m/s (Beaufort Scale of 2) in a fully developed sea (rollover image to activate motion). The image is for a 250 × 250 m area, sampled at 1 meter. The vertical scale is exaggerated, but the significant wave height is 3.1 m and the maximum vertical variation in the scene is 4.8 m.
The OCEANUS™ 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 code. The OCEANUS™ model has also been integrated into GAIA™ to provide seamless scene generation anywhere on the surface of the earth.
More details on the modeling capabilities can be found in the OCEANUS™ brochure.