The submillimeter spectra of the planets: Narrow-band photometry

Multicolor submillimeter observations of Jupiter, Saturn, Mars, and Uranus are reported. Narrow-band filters are used to define three passbands between 300 and 1600 μm to give accurate spectrophotometric data. A method for determining the atmospheric opacity from a single set of multicolor observations of a known source is shown to be consistent with secant plot data taken during very stable observing conditions. Such extinction data show that in the submillimeter region significant fluctuations in opacity occur over periods as short as 1 hr. At the time of observation the rings of Saturn were nearly edge-on and thus the disc brightness is determined without contribution from the ring emission. Comparisons with data obtained at earlier epochs give an estimate of the ring brightness as a function of wavelength. The disc emission spectra for Saturn, Jupiter, and Uranus are compared with various atmospheric models and other observations