Changes in the radiometric sensitivity of SeaWiFS determined from lunar and solar-based measurements

Abstract

We report on the lunar and solar measurements used to determine the changes in the radiometric sensitivity of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). Radiometric sensitivity is defined as the output from the instrument (or from one of the instrument bands) per unit spectral radiance at the instrument's input aperture. Knowledge of the long-term repeatability of the SeaWiFS measurements is crucial to maintaining the quality of the ocean scenes derived from measurements by the instrument. For SeaWiFS bands 1-6 (412-670 nm), the change in radiometric sensitivity is less than 0.2% for the period from November 1997 through November 1998. For band 7 (765 nm), the change is approximately 1.5% and for band 8 (865 nm) approximately 5%. The rates of change of bands 7 and 8, which were linear with time for the first eight months of lunar measurements, are now slowing. The scatter in the data points about the trend lines in this analysis is less than 0.3% for all eight SeaWiFS bands. These results are based on monthly measurements of the moon. Daily solar measurements using an onboard diffuser show that the radiometric sensitivities of the SeaWiFS bands have changed smoothly during the time intervals between lunar measurements. Because SeaWiFS measurements have continued past November 1998, the results presented here are considered as a snapshot of the instrument performance as of that date.

Biospheric Primary Production During an ENSO Transition

“…For SeaWiFS NDVI data, cloud artifacts were reduced by applying a maximum 5 by 5 pixel spatial filter over evergreen broadleaf forest regions and a median 5 by 5 pixel spatial filter and a Fourier Adjustment over all other land surfaces (31,32). (29,30). Briefly, monthly lunar observations were used to check the stability of all SeaWiFS wave bands (6), and daily solar calibrations were used to verify the high-frequency stability of the sensor.…”

Experimental Approach of Reflectance Based Vicarious Calibration Method for Solar Reflectance Wavelength Region of Sensor Onboard Remote Sensing Satellites

“…In order to investigate the trends in the estimates for calibration factors will be considered as limited to only the data that satisfies the following conditions. Conditions: Sunny, from 11:00 12:00 (average), 1 or less cloud cover 9:00, visibility 10km, Dongfeng 3 Weather conditions of these were with reference to the observations by the Japan Meteorological Agency. For the day of fine weather there is no effect of clouds on the observation of the sky radiometer, (the same applies to cloud cover) that can be expected estimate of aerosol stable.…”

“…Further, the average trend of the complex refractive index imaginary part of Figure 6 (b) is the complex refractive index and the imaginary (calibration coefficients tendency similar trend calibration factor Sky radiometer in Figure 2 As is clear from this table there is shown portion is high in the first phase, and low in the second phase, and a) shows high values in the third phase, estimation of the complex index of refraction can be seen that it has much to do with the calibration factor. That is, as described above, I assumed that fall into a local solution 3 http://www.jma.go.jp/jma/index.html 29 | P a g e www.ijarai.thesai.org in iterative methods for calibration accuracy is insufficient; the estimation accuracy of the complex refractive index imaginary part is reduced.…”

VIIRS Reflective Solar Bands Calibration Progress and Its Impact on Ocean Color Products

“…The Moon is known to have a very stable reflectance in the VIS and NIR spectral regions [18] and has been widely used to track the RSB on-orbit gain changes [41][42][43]. Since the lunar surface is not smooth, the lunar irradiance instead of the lunar radiance is used for the RSB calibration.…”