The Galileo Ultraviolet Spectrometer investigation used data obtained by two instruments. The Ultraviolet Spectrometer (UVS) covers the wavelength range from 113 to 432 nm. The Extreme Ultraviolet Spectrometer (EUV) was added to the Orbiter payload after the Challenger accident in 1986. The EUV instrument is an objective grating spectrograph covering the wavelength range from 54-128 nm in 128 contiguous intervals of 0.59 nm.
UVS Science Objectives
Observe jovian clouds and hazes repeatedly over a wide range of phase angle and wavelength. Obtain the single-scattering albedo from photometric measurements and sample the lower end of the aerosol size distribution down to 200 nm.
Measure temporal variability in the properties of clouds and hazes will be investigated at time scales ranging from days to the duration of the mission.
Determine the composition of the stratosphere by using reflectance spectroscopy during disc and limb scans to compile and inventory numerous hydrocarbons (such as methane, acetylene, and ethane) as a function of location and altitude.
Determine stratospheric temperatures through the scale height of the signal from Rayleigh-scattered sunlight.
Investigate the spectral, horizontal, vertical, and diurnal variation of the thermosphere with the UVS and EUV instruments.
Observe the aurora near the northern or southern limbs. Galileo's mostly equatorial orbits allow excellent longitudinal resolution at the cost of lesser latitude resolution.
Galileo will also allow comparison of day-side and night-side auroral emissions.
Measure and map the UV albedos of areas of jovian satellites and look for evidence of tenuous and possibly sporadic atmospheres that might be produced by sublimation or sputtering by co-rotating plasma, or even eruptive events.
In conjunction with the EUV instrument, the UVS will measure the abundance and distribution of the neutral and ionized species existing in the Io torus.