All mean differences were computed using granules taken at about 30 degrees North so as not to include any latitudinal effects. The mean of the sensor view angle change (the angle the sensor view angle is rotated through in going to the new navigation) is shown on the plot below at various times through the CZCS mission. Plot of mean sensor change through the mission In general, the zenith angle difference ( new - old) ranged from -2.5 to 2.5 degrees and the azimuth difference ranged from -7 to 12 degrees. Note the discontinuity in the zenith angle that occured with the old sensor calculation near the lowest zenith angle. Along the line, at pixel values 492, 984, and 1476 are plotted letters: O for the old values and N for the new values, to show the old and new azimuth and zenith. The old values are plotted as the thin solid line while the new values are plotted as the thick line.
The new sensor azimuth and zenith is compared to the old values for 1 line of data (line 8000) from the file C1978337171133.L2_MLAC. Plot of 1 line: sensor azimuth vs sensor zenith
The following is a characterization of the changes in the sensor view angles that resulted from the change. Nimbus 7 orbit position and velovity data, available with SMMR data, allowed the computation of the satellite position, which when combined with the observation positions on the earth, result in improved sensor view angles. The assumptions would cause the sensor angles to be off from the correct values, resulting in incorrect computations of the Rayleigh and aerosol effects. In previous versions of the CZCS data, the sensor zenith and azimuth angles were derived using a general assumption about the satellite height and the attitude angles combined with the surface latitudes and longitudes.
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