Abstract
The Atmospheric Infrared Sounder (AIRS) on the EOS Aqua Spacecraft was launched on 4 May 2002. The AIRS is designed to measure atmospheric temperature and water vapor profiles and has demonstrated exceptional radiometric and spectral accuracy and stability in orbit. The International System of Units (SI)-traceability of the derived radiances is achieved by transferring the calibration from the Large Area Blackbody (LABB) with SI traceable temperature sensors, to the On-Board Calibrator (OBC) blackbody during preflight testing. The AIRS views the OBC blackbody and four full aperture space views every scan. A recent analysis of pre-flight and on-board data has improved our understanding of the measurement uncertainty of the Version 5 AIRS L1B radiance product. For temperatures greater than 260 K, the measurement uncertainty is better than 250 mK 1-sigma for most channels. SI-traceability and quantification of the radiometric measurement uncertainty is critical to reducing biases in reanalysis products and radiative transfer models (RTMs) that use AIRS data, as well as establishing the suitability of AIRS as a benchmark for radiances established in the early 2000s.
Highlights
We evaluate the measurement uncertainty of Atmospheric Infrared Sounder (AIRS) as the RSS of the uncertainty in the radiometric calibration coefficients and estimated changes in the On Board Calibrator (OBC) emissivity, mirror polarization, correlated noise, and drift during a scan line
The radiometric measurement uncertainty in the AIRS L1B Version 5 (V5) ranges amongst the channels from
The estimated uncertainty of AIRS can be said to be very good considering the instrument was intended to be used for weather forecasting, where biases are tuned out
Summary
IR sounders operating today include the Atmospheric Infrared Sounder (AIRS) on the NASA Aqua satellite [1], the Cross-track Infrared Sounder (CrIS) on the NASA/NOAA Suomi NPP and NOAA JPSS satellites [2], the Infrared Atmospheric Sounding Interferometer (IASI) on the EUMETSAT MetOp satellites [3], the Hyperspectral Infrared Atmospheric Sounder (HIRAS) on the CMA FY-3 satellites [4], the Geostationary Interferometric Infrared Sounder on the CMA FY-4A satellite [5], and the advanced infrared (IR) sounder IKFS-2 on the Russian Meteor-M satellite [6] All of these instruments are ‘hyperspectral’, having very high spectral resolution (>1000) enabling the resolution of CO2 and H2O absorption features used to make temperature and water vapor profiles. The sounders mReemaostue Sreens.u2r0f1a9c, e11t,exmFOpRerPaEtEuRreRaEVnIdEWemissivity, cloud top height, cloud liquid water and cloud frac2toiof n25
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