Ultraviolet Spectrometer UVS and Extreme Ultraviolet Spectrometer EUV

Galileo carried two instruments for measuring UV radiation, the UVS and the EUV. The UVS was mounted on the scan platform and could thus be freely pointed. The EUV, however, was on the spun-section and thus observed only a narrow ribbon of space perpendicular to the spin axis.

The UVS was a grating spectrometer utilizing a 25 cm diameter Cassegrain telescope. There were three photomultiplier detectors, which by scanning the grating covered the spectral ranges 113 nm to 192 nm, 282 nm to 432 nm, and 162 nm to 323nm, respectively, at a spectral resolution of 0.7nm below 190nm and 1.3nm above. The FOV was 17.4 x 1.7mrad (1 x 0.1°) for the first two detectors, and 7 x 1.7mrad (0.4 x 0.1°) for the third detector.

The EUV also had a 25 cm aperture telescope system, but had a fixed grating and array of 128 contiguous detecting elements. Hence, the design was very similar to the Voyager UVS. The spectral range was 54 nm to 128 nm and thus each detector had a theoretical resolution of 0.59 nm. However, other instrumental effects meant that the resolution was 3.5 nm for extended sources and 1.5 nm for point sources. The instrument FOV was 3 x 15mrad (0.17 x 0.87°).

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