Radiometric sensitivity contrast metrics for spectral remote sensors

Abstract

The calculation, interpretation, and implications of radiometric sensitivity metrics for Earth-observing multispectral and hyperspectral imaging sensors are discussed. The most commonly used sensor performance metric is signal-to-noise ratio, from which additional noise equivalent quantities can be computed, including noise equivalent spectral radiance (NESR), noise equivalent delta reflectance ( NE Δ ρ ), noise equivalent delta emittance ( NE Δ ϵ ), and noise equivalent delta temperature ( NE Δ T ). For hyperspectral sensors, these metrics are typically calculated from an at-aperture radiance (typically generated by MODTRAN) that includes both target radiance and nontarget (atmosphere and background) radiance. Unfortunately, these calculations treat the entire at-aperture radiance as the desired signal, even when the target radiance is only a fraction of the total (such as when sensing through a long or optically dense atmospheric path). To overcome this limitation, an augmented set of metrics based on a contrast signal-to-noise ratio, including their noise equivalent counterparts (CNESR, CNE Δ ρ , CNE Δ ϵ , and CNE Δ T ), is developed. These contrast metrics better quantify sensor performance in an operational environment that includes remote sensing through the atmosphere.