Calibrating a System of Satellite Instruments - Satellite-based Applications on Climate Change - page 27

is recognized that while this issue is being resolved with hyperspectral systems, it
will remain to be an issue for broadband instruments, and new technologies are
desirable to introduce fundamental changes in these areas. One such technology on
the horizon is the quantum cascade laser (or tunable laser) calibration systems
which potentially will allow us to perform on-orbit spectral and radiometric cali-
bration. The use of such systems for vicarious calibration should also be explored in
the future.
2.6 Concluding Remarks
It is essential to establish the on-orbit calibration consistency among all Earth-
observing satellite radiometers for climate change detection, numerical weather
prediction, reanalysis, and implementation of GEOSS. This presents a significant
challenge to the current operational satellite radiometers in space, and therefore
rigorous calibration and intercalibration are needed. On-orbit calibration traceabil-
ity is required for all radiometers, which can be achieved by establishing the long-
term time series of inter-satellite calibration at the SNOs, GEO/LEO nadir points,
and selected vicarious sites for a constellation of operational satellites. This will tie
all satellite radiometers together to provide traceability of individual satellites to a
calibration reference network. The absolute accuracy can then be established
through absolute on-orbit radiometers such as those on the CLARREO (Climate
Absolute Radiance and Refractivity Observatory) and with the help of in situ and
aircraft campaigns. The system will help us diagnose radiance biases for reanalysis,
data assimilation, and time series analysis for climate change detection. It will also
bring together a world of radiometers to facilitate the implementation of GEOSS.
Acknowledgements The authors would like to thank Drs. Pubu Ciren, Likun Wang, and Bob
Iacovazzi for providing part of the data used in this chapter. We also thank Dr. Lawrence Flynn of
NOAA/NESDIS/STAR and Dr. Shucai Guan of NOAA/NCEP/NCO for a critical review of the
manuscript with constructive comments and suggestions. The manuscript contents are solely the
opinions of the author and do not constitute a statement of policy, decision, or position on behalf of
NOAA or the US government.
References
Barnes RA, Eplee RE, Patt FS, Kieffer HH, Stone TC, Meister G, Butler JJ, McClain CR (2004)
Comparison of SeaWiFS measurements of the moon with the U.S. Geological survey lunar
model. Appl Opt 43:5838-5854
Cao C, Heidinger A (2002) Inter-comparison of the longwave infrared channels of MODIS and
AVHRR/NOAA-16 using simultaneous nadir observations at orbit intersections, Earth observ-
ing systems VII. In: Barnes W (ed) Proceedings of SPIE, vol 4814, Seattle, 2002, pp 306-316