Signature & Atmospherics Library for Sensors & Out-the-Window Visuals

SigSimRT™ (see datasheet) is an advanced signature synthesis and atmospheric propagation runtime library for radiometrically-correct sensor displays and Out-the-Window (OTW) visuals. It provides on-the-fly physics-based modeling over the 0.2 – 25.0 µm spectrum (UV, visible, near-IR, thermal-IR) and for arbitrary RF frequencies. SigSimRT‘s ultra-fast algorithms and common material/property attributed Synthetic Environment make it ideal for real-time multi-sensor, OTW, CGF/SAF, and Hardware-In-The-Loop (HWIL) applications.

With SigSimRT, developers can upgrade their existing OTW IG or 3D simulation capability into radiometrically-correct spectral sensor simulations such as UV, NVG, FLIR and radar. Additionally, SigSimRT can make your existing OTW simulations physically correct for striking realism.

Natural & Man-made Source Modeling

For any 3D location, time, date and atmosphere/weather condition, SigSimRT instantly provides all the natural source quantities necessary for accurate lighting, reflectance and thermal loading, including:

  • Solar position, direct/diffuse spectral irradiance
  • Lunar position/phase, direct/diffuse spectral irradiance
  • Stellar constellation positions and spectral irradiances
  • Downwelling sky and cloud spectral irradiances
  • Upwelling earthshine spectral irradiance

In addition, SigSimRT instantly provides the correct spectral radiance from man-made light sources, including tungsten, sodium, mercury, neon, and polymetallic lamps.

Atmospheric Propagation

SigSimRT uses innovative, extremely-fast path-integral/transport algorithms based on Modtran & Radtran-atmospheric physics licensed from AFRL. These algorithms operate on a common atmospheric data model, allowing the user to assign such parameters as the pressure, temperature, molecular species concentrations and weather state at any position in the WGS-84 3D atmospheric model. SigSimRT allows changes in atmospheric state or weather conditions on-the-fly, and provides real-time updates for the source irradiances and LOS atmospherics. SigSimRT atmospherics modeling includes transmittance, thermal path radiance and scattering –all completely correlated across sensor bands for the correct relative behavior.

SigSimRT provides real-time OpenGL2.0 and Open Scene Graph (OSG) translation APIs for light source, signature and atmospherics constructs.

Common, Material/Property-Encoded Synthetic Environment

In addition to a common atmospheric data-model, SigSimRT employs a common terrain and object data-model with the innovative Material Systems Concept (supported in a SEDRIS EDCS). Material systems allow the assignment of material configurations from a comprehensive library, and associated boundary conditions to texels, vertices and/or facets in the database. In this manner, fast SigSimRT algorithms retrieve the intrinsic physical properties and conditions such as density, thermal conductivity, specific heat, BRDF, RCS, scatter-center tables, wind speed, engine-state, etc. to synthesize the correct passband signature for EO, IR or RF

Thermal Emission & Reflectance

SigSimRT has ultra-fast, full-transient thermal model algorithms that respond on-the-fly to changes in boundary conditions, such as ambient wind-speed and air temperature, rain-rate, engine states, Mach number, time-of-day and surface-normal-dependent solar loading, sky loading, etc.

Responding to the time-of-day, atmospheric condition, weather and object states, SigSimRT gives the right thermal response. Therefore, SigSimRT correctly models effects such as the diurnal cycle phenomena of “thermal cross-over” at dusk and thermal inversion of vegetation with the background at night.

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