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Molecular Oxygen Distribution

NSSDCA ID: 1967-042A-03

Mission Name: Ariel 3
Principal Investigator:Dr. Kenneth H. Stewart


The experiment was designed to measure the concentration of molecular oxygen in the earth's atmosphere at heights from 150 km to about 300 km, with wide geographical coverage. At these heights, solar ultraviolet light (1425 to 1490 A) is strongly absorbed by molecular oxygen and relatively unaffected by any other atmospheric gas. Hence, by measuring the attenuation of solar ultraviolet light as the satellite entered and left the earth's shadow, the distribution of molecular oxygen in the atmosphere could be deduced. The sensors consisted of four gas-filled ionization chambers. The instrument was mounted on the top of the satellite with the chambers displaced at right angles to each other. The output from each chamber connected into a single electrometer amplifier that then fed straight to the telemetry, the data being telemetered only on a real-time basis. Approximately 30 observations a day were taken, but only about one-third of the measurements could be recorded because many of the observations were taken beyond range of a telemetry station. The experiment was a success in spite of the rapid deterioration of the sensors under the action of solar radiation. The observed half-life of 20 days was close to that predicted as a result of laboratory tests on the ionization chambers. For a further description of the experiment, see K. H. Stewart and P. J. L. Wildman, "Preliminary results of molecular oxygen observations from the Ariel III satellite," Proc. Roy. Soc. A, v. 311, pp. 591-600, 1969.

Alternate Names

  • Ariel3/MolecularOxygenDistribution

Funding Agency

  • Science Research Council, UK (United Kingdom)


  • Earth Science: Atmospheric Chemistry
  • 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
Mr. T. L. Van RaalteOther InvestigatorAustralian Weapons Research Establishment
Dr. Kenneth H. StewartPrincipal InvestigatorMeteorological Office
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