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Visual - NearIR Analysis

Near IR Rendering

The MuSES Near-IR Extension enables rendering of low-light scenes for simulating night vision systems. By rendering in the near-IR band, MuSES software can accurately compute the contrast of targets and clutter against realistic sea surfaces and terrain backgrounds. Full target-background interaction is modeled, accounting for direct and diffuse lunar shadows, reflections and glints. By using MuSES software as the platform for electro-optic analysis of targets in any global location, comprehensive studies can be performed across near-IR, short-,mid-, and longwave-IR bands. Surface treatments and material choices can be assessed for concealment and detection, or to train a classifier for probability of detection under various weather conditions, terrain types, and lighting conditions.

Features of the Near-IR Extension

The Near-IR Extension extends the effective sensor band range in MuSES and supports four environmental sources of radiance across the near-IR waveband: Lunar glow, accounting for phase and ephemeris; atmospheric glow from chemical reactions in the stratosphere; skyshine from twilight and stars; and urban glow, modeled empirically from user-defined city populations. MuSES performs a full multi-bounce diffuse radiance computation based on global position and weather conditions, followed by a rendering with BRDF from the sensor position. Target contrast is computed, including background interaction with shadows and reflections.

Atmospheric Sources

In addition to sky and lunar sources, the MuSES Near-IR Extension supports natural atmospheric glow (also called nightglow). Nightglow is generated through numerous processes, including cosmic rays striking the upper atmosphere and chemiluminescence from hydroxyl radicals. The Near-IR Extension supports nightglow through an empirical method of computing the radiance across the sensor band, and integrating it into the sky radiance value.

Lunar Sources

A built-in Lunar ephemeris and phase model provide accurate lunar intensity based on target global position and time. Lunar radiance is computed using MODTRAN and is partitioned between direct (beam) and diffuse (scattered by clouds and atmosphere) based on the cloud coverage level in model weather data. MODTRAN is called for key points over the visible sky patch (including the lunar source).

Lunar radiance and sky shine can be rapidly computed using a broad-band method or integrated spectrally for highest accuracy. The diffuse portion of lunar radiance is integrated into the sky radiance value as described at right. Lunar glints from target surfaces are rendered and supported for structured an unstructured seas. Atmospheric attenuation is spectrally computed from all facets along the sensor line-of-sight.