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Errors from Rayleigh-Jeans approximation in satellite microwave radiometer calibration systems
1National Environmental Satellite, Data & Information Service, National Oceanic and Atmospheric Administration, College Park, Maryland 20740, USA.
Applied Optics
|January 23, 2013
Summary
The Advanced Technology Microwave Sounder (ATMS) calibration has biases up to 1-2 K due to the Rayleigh-Jeans approximation. This error, impacting satellite atmospheric measurements, increases with frequency and depends on scene count.
Area of Science:
- Earth Science
- Atmospheric Science
- Radiometry
Background:
- The Advanced Technology Microwave Sounder (ATMS) is crucial for satellite-based atmospheric measurements.
- ATMS onboard the Suomi National Polar-orbiting Partnership (SNPP) satellite uses a two-point calibration equation.
Purpose of the Study:
- To evaluate the impact of the Rayleigh-Jeans approximation on ATMS calibration biases.
- To quantify the errors introduced by this approximation in radiometric measurements.
Main Methods:
- Analysis of the ATMS sensor data record algorithm.
- Evaluation of the two-point calibration equation's validity under the Rayleigh-Jeans approximation.
Main Results:
- The Rayleigh-Jeans approximation introduces radiometric calibration errors of 1-2 K for ATMS.
- These errors are dependent on the Earth scene count and increase with higher frequencies.
Conclusions:
- The commonly used Rayleigh-Jeans approximation in ATMS calibration leads to significant biases.
- Accurate atmospheric temperature retrieval requires addressing these calibration biases, especially at higher frequencies.
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