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Imaging Photopolarimeter (IPP)

NSSDCA ID: 1973-019A-07

Mission Name: Pioneer 11
Principal Investigator:Dr. Tom Gehrels


The Imaging Photopolarimeter (IPP) experiment used during Jovian and Saturnian encounter made simultaneous, two-color (blue - 3900 to 4900 A, red - 5800 to 7000 A) polarimetric and radiometric measurements, and moderate-resolution (about 200 km at best) spin-scan images of Jupiter and the Jovian satellites and Saturn and some of its satellites. The polarimetric and radiometric work was performed using an 8- by 8-mrad field-stop aperture, while the spin-scan imaging used a 0.5- by 0.5-mrad aperture stop. Relative radiometric calibration was derived using an internal tungsten lamp. Long-term absolute calibration of the instrument was accomplished by means of a sunlight diffusor/attenuator element located in the spacecraft antenna structure. Primary radiometric calibration was obtained throughout the mission by periodically commanding the telescope to view this diffuse backlighted (sunlight) source. The experimental train for the IPP package consisted of the following elements: (1) a near-diffraction-limited 2.54-cm Maksutov telescope of focal ratio f/3.4, (2) a focal-plane wheel containing field-of-view (FOV) apertures, depolarizers, calibration source, etc., (3) a Wollaston prism to split the light into two orthogonally polarized beams, (4) a 45-deg dichromatic mirror that reflected wavelengths of less than 5500 A (blue beam) and transmitted all light of longer wavelength (red beam), (5) a filtering-coated relay lens and folding mirrors for each spectral beam (the two polarizations were separated), and (6) two Bendix channeltron (blue - bialkali S-11, red - S-20) photocathodes for each spectral beam to register the intensity in each polarization component. Polarization data included the interplanetary region. This instrument was originally turned off in February 1984 but is periodically used now to gather star roll and cone angle information for use in spacecraft attitude determination.

Alternate Names

  • IPP
  • Pioneer11/IPP

Funding Agency

  • NASA-Office of Space Science (United States)


  • Planetary Science: Atmospheres
  • Planetary Science: Small Bodies
  • Astronomy: Visible
  • Planetary Science: Geology and Geophysics

Additional Information

Questions and comments about this experiment can be directed to: Dr. John F. Cooper



NameRoleOriginal AffiliationE-mail
Dr. David L. CoffeenOther InvestigatorNASA Goddard Institute for Space Studies
Prof. Kaarle A. Hameen-AnttilaOther InvestigatorUniversity of Arizona
Mr. Robert F. HummerOther InvestigatorSanta Barbara Research Center
Dr. Charles E. KenknightOther InvestigatorUniversity of Arizona
Dr. Martin G. TomaskoOther InvestigatorUniversity of
Mr. W. SwindellOther InvestigatorUniversity of Arizona
Dr. Tom GehrelsPrincipal InvestigatorUniversity of Arizona
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