Extended Abstract (104K)P5.29
The Calibration of NOAA-AVHRR Visible Radiances with VIRS
David R. Doelling, AS&M, Hampton, VA; and V. Chakrapani, P. Minnis, and L. Nguyen
The NOAA Advanced Very High Resolution Radiometer (AVHRR) instruments do not have onboard calibration in the visible wavelengths. Currently, AVHRR uses spectrally stable surface targets, such as deserts, and corrections for atmospheric absorption and scatrering to adjust the observed radiances to a standard value (Rao & Chen, 1998). This process is only performed for the afternoon NOAA satellite, currently NOAA-16, beginning with NOAA-9. Since the spectral response functions on the AVHRR instruments are nearly identical, cross calibration of the morning and afternoon polar orbiting satellites can be performed at 81° North or South latitudes where the orbits intersect. This is accomplished using coincident, co-angled, and co-located radiances. The NOAA-14 AVHRR is calibrated using VIRS (Minnis et al., 2001) and used as a transfer medium for calibrating other morning and afternoon NOAA satellites at the poles. Also the relative filter degradation trend between satellites can also be determined. The same technique can be applied to other visible scanning instruments that have onboard solar diffusers and AVHRR given that the channel spectral response functions are similar. This will give an independent assessment of the standard Rao and Chen calibration now being provided for NOAA-14. It has been shown that VIRS has a stable visible calibration using an onboard solar diffuser, when compared against ATSR and MODIS. Using geostationary radiances as an intermediate calibration reference point increases the number of matched data points. The geostationary cross-calibration is validated by completing a three way circular calibration. This paper will provide the 0.65um visible calibration coefficients as a function of days since launch for all NOAA instruments operating from 1985 to present. IR channel intercomparisons will also be shown. This technique can provide continuous ongoing calibration
Supplementary URL: http://www-pm.larc.nasa.gov
Poster Session 5, New Technology and Methods
Wednesday, 17 October 2001, 2:15 PM-4:00 PM
Previous paper Next paper