Infrared spectral responsivity scale realization and validations

Area of Science:

• Metrology
• Radiometry
• Infrared Spectroscopy

Background:

• Indium antimonide (InSb) radiometers are crucial for spectral measurements.
• Accurate calibration scales are essential for reliable radiometer performance.
• Previous calibrations relied on cryogenic bolometers and inter-laboratory comparisons.

Purpose of the Study:

• To realize and disseminate a new spectral power responsivity scale using a pyroelectric transfer standard.
• To validate the calibration and long-term stability of an InSb working standard radiometer.
• To verify spectral irradiance responsivity scales for infrared (IR) target simulator calibration.

Main Methods:

• Calibration of an InSb working standard against a cryogenic bolometer (NIST, 1999).
• Calibration of the InSb standard against a newly developed pyroelectric transfer standard.
• Inter-laboratory comparison with the National Physical Laboratory (NPL, UK) in 1999.
• Utilized the InSb standard in irradiance measurement mode.

Main Results:

• A new NIST spectral power responsivity scale was realized between 1.7 and 14 μm with 1% uncertainty (k=2).
• Disagreements below 2% were found between NIST, NPL, and pyroelectric standard calibrations for the InSb working standard.
• Spectral irradiance responsivity scale uncertainty is 2.5% (k=2) from 2 to 5.2 μm.

Conclusions:

• The pyroelectric transfer standard successfully disseminates the NIST spectral power responsivity scale.
• The InSb working standard demonstrates excellent long-term stability and validates independent calibration scales.
• The InSb standard's irradiance responsivity is validated for calibrating IR target simulators.