Calibration of coherent lidar targets

Area of Science:

• Optics and Photonics
• Remote Sensing
• Materials Science

Background:

• Accurate calibration of remote sensing instruments is crucial for reliable data acquisition.
• Bidirectional reflectance distribution function (BRDF) measurements are essential for understanding surface-target interactions.
• Atmospheric effects like turbulence-induced beam wander can significantly impact remote sensing measurements.

Purpose of the Study:

• To determine the backscatter reflectance of specific abrasive materials (aluminum oxide and silicon carbide) at a 10.6 micrometer wavelength.
• To evaluate the influence of atmospheric turbulence on beam wander for rotating and translating surfaces.
• To present the benefits of using large, slowly rotating disks for field calibration procedures.

Main Methods:

• Measurement of bidirectional reflectance distribution function (BRDF) at a 45-degree incidence and observation angle.
• Utilized circularly polarized radiation at a wavelength of 10.6 micrometers.
• Analyzed the effects of range and atmospheric turbulence on beam wander for different surface movement types (rotating disks, translating belts).

Main Results:

• Quantified backscatter reflectance for 120-grit aluminum oxide (1.5 x 10^-2 sr^-1) and 400-grit silicon carbide (1.1 x 10^-2 sr^-1) relative to sublimed sulfur (1.8 x 10^-1 sr^-1).
• Discussed the impact of atmospheric turbulence-induced beam wander on measurement accuracy.
• Identified advantages of large, slowly rotating disks for practical field calibrations.

Conclusions:

• The study provides critical backscatter reflectance data for common abrasive materials relevant to remote sensing.
• Understanding and mitigating atmospheric turbulence effects are vital for accurate field calibrations.
• Large, slowly rotating disks offer a practical and advantageous approach for in-situ calibration of optical instruments.