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Radio Propagation

NSSDCA ID: 1964-054A-05

Mission Name: OGO 1
Principal Investigator:Dr. John K. Hargreaves


This experiment was used to explore the exosphere by studying the behavior of the columnar electron content between ground and satellite as the spacecraft rose from perigee in its very eccentric orbit. Simultaneous measurements were made of the differential Doppler frequency and the Faraday rotation angle. The instrumentation consisted of a pair of radio beacons operating at harmonically related frequencies (40.01 and 360.09 MHz), which were modulated by 20- and 200-kHz signals. The 40-MHz transmitting antenna was a simple dipole with a gain of 2 dB, while the 360-MHz antenna was a Yagi with a gain of 8 dB. Signals were received by two sets of tracking antennas at Boulder from a maximum distance of 60,000 km. Each set of tracking antennas consisted of a 28-ft paraboloid to receive the 360-MHz signal and a 6-element Yagi to receive the 40-MHz signal. In using Faraday rotation techniques on the 40-MHz signal, the electrons affecting the signal are assumed to occur near the foF2 maximum. In the Doppler (also called group-delay or modulation-phase) technique, the total electron content (TEC) is independent of the electron density distribution. The two kinds of TEC measurements should thus be comparable at lower altitudes. At higher altitudes, the measurements should differ due to electrons which are far removed from the foF2 maximum. OGO 1 was planned as an earth-stabilized satellite, but difficulties that appeared immediately after launch caused the satellite to spin at a rate of about 5 rpm. This introduced a number of unexpected complications in the interpretation and analysis of the data. The spin axis orientation was not precisely known. Values of 42.5 deg in right ascension and -9 deg in declination, suggested by independent experiments, were used in interpreting the beacon data, although the results did not require an accurate knowledge of this orientation. During winter (January and February) and summer (June through August) months, there was insufficient spacecraft power due to the unfavorable sun angle. During the remaining months, observations of several hours were possible once or twice during each 8-day period. On May 27, 1967, this experiment produced interference with the command receiver and the experiment was turned off when the interference problem was confirmed as being caused by this experiment.

Alternate Names

  • OGO1/RadioPropagation

Facts in Brief

Mass: 0.5 kg
Power (avg): 4 W

Funding Agency

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


  • Space Physics: Ionospheric Studies

Additional Information

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



NameRoleOriginal AffiliationE-mail
Mr. Richard B. FritzOther InvestigatorNOAA Environmental Research Laboratories
Dr. Owen K. GarriottOther InvestigatorNASA Johnson Space Center
Mr. Robert S. LawrenceOther InvestigatorNOAA Environmental Research
Dr. John K. HargreavesPrincipal InvestigatorUniversity of Lancaster
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