A survey of Saturn's Northern Hemisphere from 1979 to 1987

A photographic survey in four spectral regions (ultraviolet, blue, visible and red) of the Northern Hemisphere of Saturn's atmosphere, has been carried out between 1980 (epoch of the edgewise apparition of the rings) and 1987 (ring's maximum aperture), with the aim of analyzing the changes in the cloud morphology and reflectivity with respect to the spacecraft aspects in 1979 (Pioneer 11) and 1980–1981 (Voyager 1 and 2). Very few variations were detected in the meridional position of the belts and zones ; only a shift of 4000 km toward the North appeared to occur in 1984 in ultraviolet light to the region at latitude 46°N (occupied in 1980–1981 by the “ribbon” feature). Other belts and zones remained stable to ground-based telescopic resolution during the whole period. An increase of 7% in the reflectivity ratio of the belt NEB and the zone EZ, was noted in the spectral interval from 4000 to 6500 Å last year. This can be attributed to the seasonal insolation variation.