Jupiter's spectrum between 12 and 24 micrometers

Spectroscopic measurements of the thermal radiation from Jupiter between 12 and 24 micrometers (420 to 840 reciprocal centimeters) with a resolution of 4 reciprocal centimeters are used to infer the Jovian temperature structure in the pressure region from 0.1 to 0.4 atmosphere. The brightness-temperature spectrum is in good agreement with previous ground-based measurements between 11 and 13 micrometers and with airborne measurements between 18 and 25 micrometers. However, the integrated flux calculated for a filter window and viewing angle equivalent to those of the 20-micrometer channel of Pioneer 10 is 20 per cent below that measured by the Pioneer infrared radiometer. The Q branch of the nu-5 fundamental band of acetylene at 730 reciprocal centimeters appears in emission and leads to a mixing-ratio estimate of 10 to the -6th (plus or minus 0.5) power.