GOES-8 through GOES-O Imager Spectral Response Functions
(Revised, March 2009)
The latest versions of
GOES-8 through GOES-O Imager
spectral response functions (SRFs) are now available
for download.
All of them were provided
by ITT, the instruments' manufacturer.
GOES Imager Spectral Response Function Download Table
Note that three versions of the spectral response functions (SRFs) for channel 6 (13.3
microns central wavelength) of the GOES-13 Imager are presented on this website, along
with the related calibration parameters associated with each SRF version. These different
SRFs have come about due to the identification of a cold bias in the brightness temperatures
of the channel 6 images.
Version 1: Original
The original channel 6 SRFs provided by the instrument vendor, ITT, were used during the GOES-13
post-launch tests in 2006 when a cold bias of -2.4±0.6 K in the channel 6 imagery was reported by
the CIMSS group at University of Wisconsin. The cold bias was identified via comparisons with high
spectral resolution Atmospheric InfraRed Sounder (AIRS) data on Aqua, comparisons with High-resolution
Infrared Radiation Sounder (HIRS) data on NOAA-15 and NOAA-16 and a limited number of forward model
comparisons. The cold bias is consistent with a central-wavelength shift on the order of -4 cm-1
(towards longer wavelengths) with respect to the original channel 6 SRFs. The original channel 6
SRFs are included in the above GOES-13 download
link, and they have been used for all GOES 13 Imager
calibration processing before Aug. 1, 2008 (when GOES-13 was most recently taken out of storage).
Version 2: ITT Updated
In response to the cold bias detected in channel 6 imagery during post-launch testing, ITT re-evaluated
the pre-launch test data and provided updated SRFs for channel 6 which shifted their effective central
wavelengths by about -1.2 cm-1 (towards longer wavelengths). The ITT-updated SRFs are included in the
above GOES-13 download link and the Calibration and Alignment Handbook information for GOES-13. The ITT
updated SRFs were used for all GOES 13 Imager calibration processing from Aug. 1, 2008 to March 26, 2009.
Version 3: STAR Updated
NOAA/STAR has evaluated the original cold bias findings, and it has also analyzed a set of observational
comparisons with both AIRS and IASI data for year 2008. This has led to another update to the channel 6
SRFs which shifts the ITT updated SRFs by a further -2.1 cm-1 (towards longer wavelengths). Thus the
STAR-updated SRFs have a total effective shift of about -3.3 cm-1 with respect to the original channel 6 SRFs.
The STAR-updated SRFs are included in the above GOES-13
download link, and they have been used for all GOES 13
Imager calibration processing after March 26, 2009.
The updated shifted GOES-13 Imager channel-6 SRF reduces the overall cold bias. Users need to adjust their
conversion from radiance to brightness temperature for this channel. For each of these SRF versions, the GOES
Calibration web site contains all of the coefficients for Conversion
of GVAR Infrared Data to Scene Radiance or Temperature for GOES-13 Imager channel 6.
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