SeaWiFS Solar Azimuthal Angles

Image generated April 30, 2004.

The azimuthal angle of the image of the sun on the solar diffuser. As the sun changes position in the sky over the course of a year, the incidence angle of the solar image on the diffuser changes in the direction that is perpendicular to the direction of the pitch of the spacecraft as the spacecraft maintains nadir pointing.

The change in the BRDF of the diffuser with time is not fully known, so the BRDF cannot be used in computing the azimuthal angle corrections. Consequently, empirical fits of the the diffusuer reflectance as a funtion of azimuthal angle are used to generate the corrections. The changing BRDF causes the azimuthal angle effect to change from year-to-year. As a result, the empirical fits are performed on a yearly basis, which corresponds to one full cycle in the azimuthal angle time series. The change in the BRDF of the diffuser and the resulting multiple empirical fits used to characterize this effect are the primary sources of noise in the solar calibration time series.

Return to SeaWiFS Solar Calibration Time Series.

For further information contact Gene Eplee.

Last modified: Fri Apr 8 14:59:32 EDT 2005