Wave number (cm")

Figure 7.25. Disk-integrated irradiance spectra of the giant planets recorded by ISO/SWS, measured in Janskys. In fact, the spectra for Jupiter and Saturn are not quite disk-averaged, as is described in the text. Courtesy of T. Encrenaz and T. Fouchet.

The aperture size of the instrument was set to be approximately equal to the diffraction-limited angular resolution of the ISO telescope at 200 ^m, the longest operating wavelength of LWS, and during in-flight operation the FOV was observa-tionally determined to be 80".

Observed disk-averaged LWS spectra of Jupiter and Saturn are shown in Figure 7.26. It proved in practice somewhat difficult to radiometrically calibrate this instrument, and thus the detector subspectra here do not overlap well. However, individual subspectra are correct relative to themselves and thus the depths of the ammonia absorption lines are reliable. The available LWS and SWS spectra of the giant planets have been combined in Figure 7.27 to give near-complete disk-averaged spectra. The gap between 16 ^m and 45 ^m (222-625 cm-1), which should nominally have been recorded by SWS, was not reliably measured. The ISO instruments were designed

Jupiter. 30th November 1997

Jupiter. 30th November 1997

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