True along-track scan to improve radiation budget estimations

Multiangle approaches for radiance-to-flux conversion require accurate coregistration between the observations from nadir- and oblique-viewing directions. The along-track mode of Earth Radiation Budget (ERB) scanning instruments, such as the Clouds and the Earth's Radiant Energy System (CERES), provides some multiangular observations with almost the same target observed from nadir, aft, and fore directions. To improve the overlaps of multiangle observations, this study explains how to introduce a yaw steering angle in the along-track scan mode so as to reduce the residual collocations errors. The implementation of this correction to the CERES/Terra along-track mode shows that the distances between the nadir and the oblique (55°) observations are reduced from about 40 to 2 km. Both oblique radiances are shown to be equal with small rms differences: 3.9% (all scenes) and 1.8% (homogeneous scenes), compared, respectively, to 7.0% and 3.5% before the scan adjustment.