Airborne spectroscopy of Jupiter in the 100- to 300-cm−1 region: Global properties of ammonia gas and ice haze

A spectrum of the disk of Jupiter was obtained in January 1978 from the Kuiper Airborne Observatory, covering the 100- to 300-cm^?1 spectral range at a resolution corresponding to 1.65 cm^?1. Although taken more than a year before the Voyager 1 Jupiter encounter, this spectrum serves to extend the Voyager IRIS experiment coverage down from its lower limit of 200 cm^?1. Analysis of the spectrum provides information on global mean properties of ammonia gas and an ammonia ice haze. A vertical distribution indistinguishable from saturation equilibrium, with a sharp depletion near the temperature minimum, matches the observed shape of the rotational line absorption best. Constraints on the total optical thickness of the ammonia ice haze can be made, but other properties, such as particle size or vertical scale height, cannot be distinguished clearly from our data in this spectral region. Nevertheless, all models of the haze produce a “continuum” thermal emission between the NH₃ line manifolds which is much lower than that produced by the H₂ collision-induced dipole opacity.