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Ultraviolet Spectrometer and Extreme Ultraviolet Spectrometer (UVS/EUVS)

NSSDC ID: 1989-084B-02
Mission Name: Galileo Orbiter
Principal Investigator: Dr. Charles W. Hord


The Galileo ultraviolet spectrometer investigation consists of two instruments: the Ultraviolet Spectrometer (UVS) and the Extreme Ultraviolet Spectrometer (EUVS). The primary objectives of the experiment are to: (1) study the composition and structure of the upper Jovian atmosphere; (2) determine the loss rates of volatile gases from the Galilean satellites; and, (3) examine the physical processes occurring in the Io plasma torus.

The UVS instrument consists of a Cassegrain telescope in a Dall-Kirkham configuration with an effective focal length of 250 mm (f/5) and a scanning spectrometer. Three photomultiplier detectors, situated in the focal plane of the spectrometer, cover the entire ultraviolet and near-visible spectrum between 113-432 nm. So that accurate limb profiles can be ascertained, the telescope is equipped with an external sunshade and an extensive baffle system to reject off-axis scattered light. The spectrometer is a standard, 125 mm focal length, Ebert-Fastie design using a single spherical mirror (as both a collimator and a camera) and a plane diffraction grating. The field of view for the UVS is wavelength dependent, limited by the spectrometer entrance slit to 1 degree by 0.1 degree for two of the detectors (113-192 nm and 282-432 nm) and by one of the spectrometer exit slits to 0.4 degree by 0.1 degree for the other (162-323 nm). The wavelength resolution of the UVS is 0.7 nm below 190 nm and 1.3 nm at longer wavelengths.

The EUVS is a modified flight spare of the Voyager ultraviolet spectrometer. It is an objective grating spectrograph covering 54-128 nm in 128 contiguous intervals of 0.59 nm. In addition to adapting the electrical interface to allow connection to the Galileo command and data bus, its field of view in the dispersion direction was increased by 70% and the grating changed to increase dispersion by 40%. The field of view of the EUVS is 0.17 degree FWHM in the dispersion direction and about 0.87 degree in the cross-dispersion direction. The wavelength resolution of the EUVS is about 3.5 nm for extended sources and 1.5 nm for point sources.

Alternate Names

  • EUVS
  • UVS

Facts in Brief

Mass: 9.7 kg
Power (avg): 5.9 W
Bit rate (avg): 1.0 bps

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Astronomy: Ultraviolet
  • Planetary Science: Atmospheres
  • Planetary Science: Fields and Particles
  • Planetary Science: Small Bodies

Additional Information

Questions or comments about this experiment can be directed to: Dr. Edwin V. Bell, II.



NameRoleOriginal AffiliationE-mail
Prof. Donald M. HuntenCo-InvestigatorUniversity of
Dr. Charles W. HordGeneral ContactUniversity of Colorado 
Dr. Bill Roy SandelCo-InvestigatorUniversity of
Dr. Larry W. EspositoCo-InvestigatorUniversity of
Dr. Charles A. BarthCo-InvestigatorUniversity of
Dr. A. Lyle BroadfootCo-InvestigatorUniversity of
Dr. Donald E. ShemanskyCo-InvestigatorUniversity of Arizona 
Dr. A. Ian StewartCo-InvestigatorUniversity of
Dr. William E. McClintockCo-InvestigatorUniversity of
Dr. Joseph M. AjelloCo-InvestigatorNASA Jet Propulsion
Dr. Arthur Lonne LaneCo-InvestigatorNASA Jet Propulsion
Prof. Gary E. ThomasCo-InvestigatorUniversity of

Selected References

Hord, C. W., et al., Galileo ultraviolet spectrometer experiment: Initial Venus and interplanetary cruise results, Science, 253, No. 5027, 1548-1550, Sep. 1991.

Hord, C. W., et al., Galileo ultraviolet spectrometer experiment, Space Sci. Rev., 60, No. 1/4, 503-530, May 1992.

Image of the Ultraviolet Spectrometer and Extreme Ultraviolet Spectrometer (UVS/EUVS) experiment

Ultraviolet Spectrometer and Extreme Ultraviolet Spectrometer (UVS/EUVS)

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