Radiometric calibration methods for day/night whole sky imagers and extinction imagers

Area of Science:

• Atmospheric optics
• Radiometric calibration
• Remote sensing instrumentation

Background:

• Day/night whole sky imagers (DNWSI) detect clouds and their opacity.
• Extinction imagers measure atmospheric transmittance and path extinction.
• Existing algorithms for these instruments require accurate radiometric calibration.

Purpose of the Study:

• To present new radiometric calibration methods and results for DNWSI and extinction imagers.
• To support the development of new cloud and atmospheric transmission algorithms.
• To ensure accurate absolute and relative radiance measurements from the instruments.

Main Methods:

• Developed new radiometric calibration methods for DNWSI and extinction imagers.
• Calibration steps include dark correction, linearity calibration, absolute calibration (for DNWSI), and uniformity calibration.
• Addressed challenges including fisheye lens uniformity calibration and visible/short-wave IR system calibration.

Main Results:

• Successfully calibrated DNWSI for absolute radiance measurements.
• Calibrated extinction imagers for relative radiance measurements.
• The new calibrations provide essential data for operational algorithms.

Conclusions:

• The developed radiometric calibration methods are crucial for accurate data acquisition from DNWSI and extinction imagers.
• These calibrations enhance the performance of cloud detection and atmospheric transmittance algorithms.
• The methods are applicable to both visible and short-wave infrared spectral ranges.