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Ultraviolet Imaging Spectrometer (ALICE)

NSSDCA ID: 2004-006A-03

Mission Name: Rosetta
Principal Investigator:Dr. Alan Stern


The ALICE instrument is a Roland Circle style imaging spectrograph designed to perform far-UV spectroscopy in the range of 0.07 to 0.205 micrometers (700-2050 angstroms). The scientific objectives of the instrument are: 1) determine volatalized rare gas content of the nucleus, which will provide information on the formation temperature and thermal history; 2) characterize the production rates and spatial distribution of H20, CO, and CO2; 3) make atomic budget measurements of C, H, O, N, S to profile the elemental composition of volatiles on nucleus; 4) study the onset of activity as the comet approaches the Sun; 5) spectrally map the nucleus; 6) measure the photometric properties and ice/ice/rock ratio of small grains; and 7) map the time variability of O+, N+, S+, C+ emissions in coma and ion tail.

ALICE is a 32.6 x 14.6 x 9.0 cm box mounted on the Rosetta payload support module. Light goes through an entrance aperture which is boresighted with the imager and IR spectrometer and past a series of telescope baffles which are employed to block stray light and shield the primary mirror from small particles. The light is focused by an f/3 40 x 40 mm off-axis paraboloid mirror onto an entrance slit. The beam enters the detector tube and hits an ellipsoidal reflective holographic diffraction grating, both the mirror and grating are coated with sputtered SiC to improve reflectivity. The grating disperses the beam onto a 512 x 32 pixel microchannel plate detector which uses side-by-side potassium bromide (700-1500 Angstroms) and cesium iodide (1500-2050 Angstroms) photocathodes. The detector uses an MCP Z-stack and a 3-channel wedge-and-strip readout array. The active area is 35 mm in the dispersion direction by 20 mm in the spatial dimension. The instantaneous field of view is 0.1 x 6.0 degrees and the spatial resolution is 0.1 x 0.6 degrees. The spectrograph uses the first diffraction order through the full 700-2050 angstrom spectral passband. The spectral resolution is between 9.8 and 12.5 angstroms with a spectral resolving power of 55-200.

Alternate Names

  • Rosetta/ALICE
  • urn:esa:psa:context:instrument:ro.alice

Facts in Brief

Mass: 2.2 kg
Power (avg): 2.9 W

Funding Agency

  • European Space Agency (International)


  • Planetary Science: Small Bodies

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. Alan SternPrincipal InvestigatorSouthwest Research

Selected References

  • Stern, S. A., et al., ALICE-An Ultraviolet Imaging Spectrometer for the Rosetta Orbiter, Adv. Space Res., 21, No. 11, 1517-1525, doi:10.1016/S0273-1177(97)00944-7, 1998.
  • Stern, S. A., et al., Alice: The Rosetta Ultraviolet Imaging Spectrograph, Space Sci. Rev., 128, 507-527, doi:10.1007/s11214-006-9035-8, 2007.
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