Absolute infrared radiance measurements of Venus and Jupiter

Balloon-borne measurements of brightness temperatures were made for Venus and Jupiter and are in general agreement with ground-based observations. In all these results, however, there remains a greater variation than can be explained by computed error margins. It is concluded that the absolute brightness temperatures reported here constitute a base from which the constancy of the radiation from Venus and Jupiter can be investigated to determine the usefulness of these planets as infrared calibration sources.