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Airglow Photometer

NSSDCA ID: 1967-073A-12

Mission Name: OGO 4
Principal Investigator:Mrs. Edith I. Reed


The objective of the main body experiment was to study the characteristics and distribution of airglow and auroral activity by obtaining photometric measurements of several prominent emission lines. An EMR 541E photomultiplier (trialkali cathode and sapphire window) was used with seven interference filters. With the two exceptions noted below, all the emissions in the visible and UV wavelengths were viewed in the nadir direction, i.e., directly below the spacecraft. Eight channels or modes of operation were used and were essentially generated by rotating mirrors. For each position of the mirrors, the light intensity for a particular light path through a different filter was recorded. The mirrors switched at 1-s intervals. In the 8-s interval needed to complete a measurement cycle, the satellite moved 0.5 deg latitude. In the first mirror position, the field of view was blanked, and the noise level of the sensor was measured. The next mirror position presented the nadir emission intensity through an interference filter centered at 2630 A. The third position measured zenith emission intensity through the 6300-A filter. This was the only upward-looking measurement taken. The next mirror position also passed the radiation through a 6300-A filter, except here the incoming light was from below. The fifth mirror position enabled radiation from the nadir at 6225 A to be measured. Subsequent mirror positions permitted measurement of nadir intensities at the following wavelengths: 5892, 5577, and 3914 A. The field of view was 10 deg across in the downward direction and 7 deg across looking upward. An assessment of the stability of the experiment's response was obtained by comparing measured moonlit earth radiance over oceans on repeated passes. Absolute "responsivity" was determined from the overhead transit of Saturn and Jupiter. In addition to the main body photometer, there was a photometer mounted in the OPEP that scanned the earth's limb. It projected the light through a 6300-A filter. NSSDC has all the useful data that exist from this investigation.

Alternate Names

  • OGO4/AirglowPhotometer

Facts in Brief

Mass: 13 kg
Power (avg): 11 W


  • Space Physics: Ionospheric Studies
  • Space Physics: Thermospheric Studies

Additional Information

Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Prof. Jacques E. BlamontOther InvestigatorCNRS, Service d'Aeronomie
Mrs. Edith I. ReedPrincipal InvestigatorNASA Goddard Space Flight Center
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