SPEX airborne spectropolarimeter calibration and performance.

Area of Science:

• Atmospheric Science
• Climate Science
• Optical Physics

Background:

• Aerosols significantly impact climate and air quality.
• Accurate aerosol characterization requires multiangle, multiwavelength polarimetric measurements.
• Satellite-based instruments are essential for global aerosol monitoring.

Purpose of the Study:

• To develop and validate SPEX airborne, a hyperspectral polarimeter for aerosol characterization.
• To assess the accuracy of SPEX airborne's degree of linear polarization (DoLP) and radiance measurements.
• To demonstrate SPEX airborne's capability as a precursor to space-based SPEX instruments.

Main Methods:

• SPEX airborne utilizes spectral polarization modulation for DoLP measurements.
• Radiometric and polarimetric calibration performed using Jet Propulsion Laboratory (JPL) facilities.
• In-flight intercomparison with Research Scanning Polarimeter (RSP) during a field campaign.

Main Results:

• SPEX airborne achieved laboratory DoLP measurement accuracy of 0.002-0.004.
• Radiometric calibration accuracy was estimated at 4%.
• In-flight DoLP measurements showed root-mean-square (RMS) differences of 0.004-0.02 compared to RSP.
• Radiance measurements exhibited excellent agreement with RSP (RMS difference of ~4%).

Conclusions:

• SPEX airborne successfully demonstrated high-accuracy polarimetric and radiometric measurements.
• In-flight performance validated SPEX airborne's capability to deliver high-quality aerosol data.
• The instrument serves as a vital demonstrator for future space-based aerosol monitoring missions.