<title>AIRS instrument polarization response: measurement methodology</title>

Abstract

A novel measurement methodology for determining the polarization response of optical instruments is described. The methodology was developed for testing the polarization response of the Atmospheric Infrared Sounder (AIRS), but has general applicability. The technique involves measuring the instrument's response to each of three distinct input polarization states, and computing from these signals a polarization transfer function using a special data processing algorithm. The equations that are the basis of the data processing algorithm are presented along with an outline of their derivation.The technique has been successfully used to test the polarization response of the AIRS JR Sensor Assembly as part of the Protoflight Model (PFM) Integration and Test program. The measured data shows excellent agreement with AIRS polarization response predictions, which were calculated using very complex numerical methods. A description of the test equipment are presented along with plots of the measured and predicted AIRS Spectrometer Polarization Ratio vs.wavelength.

The Effect of Instrument Polarization Sensitivity on Sea Surface Remote Sensing with Infrared Spectroradiometers

“…For a 75Њ angle the error increases to about 0.5-0.7 K in the longwave infrared region (ϳ600-1500 cm Ϫ1 ) and Ϯ0.3 K in the shortwave (ϳ2400-3400 cm Ϫ1 ) infrared spectral region. Such a large polarization sensitivity does, in fact, exist in the infrared channels of the AIRS grating spectroradiometer (Pagano et al 2000;Gigioli and Pagano 1999).…”

“…FTIR instruments use beam splitters and mirrors that usually favor one polarization state over another, creating an instrument polarization sensitivity that can cause errors in radiometric measurements of partially polarized radiance when the instrument is calibrated with unpolarized sources. The potential for polarization errors contributing significantly to the error budget of modern infrared satellite sensors also has been recognized, particularly because of polarization-dependent scan mirrors and gratings (Pagano et al 2000;Gigioli and Pagano 1999;Knight et al 1999). This issue is complicated by the variability of the scene polarization S H A W FIG.…”