Radiometric Calibration in Thermal Infrared

Abstract

Calibration is defined by the Working Group on Calibration and Validation (WGCV) of the International Committee on Earth Observation Satellites (CEOS) as the process of quantitatively defining the system response to known, controlled signal inputs (Belward 1999). The main fundamental aspects that need to be calibrated are the sensor system’s response to electromagnetic radiation as a function of (1) wavelength and/or spectral band (spectral response), (2) the intensity of the input signals (radiometric response), (3) different locations across the instantaneous field of view and/or the overall scene (spatial response or uniformity), (4) different integration times and lens or aperture setting, and (5) unwanted signals such as stray light and leakage from other spectral bands (Liang 2004). Estimating land surface bio-/geophysical variables accurately from remotely sensed data relies largely on the accuracy of radiometric calibration. Radiometric calibration is a process that coverts the observed digital numbers (DN) to physical quantities of radiance. Preflight calibration, in-flight calibration, vicarious calibration, and intercalibration are critical components of a calibration system.