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Tangent height registration method for the Version 1.4 data retrieval algorithm of the solar occultation sensor
Tomoaki Tanaka1, Hideaki Nakajima, Takafumi Sugita
1National Institute for Environmental Studies, Tsukuba, Japan. tanaka.tomoaki@nies.go.jp
Applied Optics
|October 13, 2007
Summary
The Improved Limb Atmospheric Spectrometer-II (ILAS-II) precisely registers tangent heights for atmospheric trace gas measurements. This method ensures accurate vertical profiles, with errors within 7% for a 100m altitude shift.
Area of Science:
- Atmospheric science
- Remote sensing
- Satellite instrumentation
Background:
- The Improved Limb Atmospheric Spectrometer-II (ILAS-II) is a satellite sensor for observing atmospheric trace constituents.
- Accurate measurement of gas volume mixing ratios relies heavily on precise tangent height determination.
Purpose of the Study:
- To describe the tangent height registration method used in the ILAS-II Version 1.4 data retrieval algorithm.
- To assess the accuracy and impact of tangent height errors on atmospheric profile data.
Main Methods:
- Development and application of a "combination method" for tangent height registration.
- Geometric determination of tangent heights using a Sun-edge sensor.
- Estimation of random and systematic errors in tangent height determination.
Main Results:
- The combination method provides appropriate tangent heights for the ILAS-II Version 1.4 retrieval algorithm.
- Estimated root-sum-square total random error is 30 m and total systematic error is 180 m at 30 km altitude.
- Relative differences in gas volume mixing ratios are within 7% for a +/-100 m altitude shift and 20% for a +/-300 m shift.
Conclusions:
- The developed tangent height registration method is crucial for accurate ILAS-II atmospheric measurements.
- Tangent height errors have a quantifiable impact on trace gas profile data, with minimal impact within +/-100 m.
- The ILAS-II Version 1.4 data retrieval algorithm, using this method, provides reliable atmospheric composition data.
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