NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

VLF Electromagnetic Radiation

NSSDCA ID: 1962-067B-09

Mission Name: Injun 3
Principal Investigator:Prof. Donald A. Gurnett


This experiment was designed to study very low frequency (VLF) noise phenomena received at low earth-orbital altitudes. It was possible that noise sources included man-made signals from the ground or satellites, spherics, ionospheric or magnetospheric noise, and noise from other extraterrestrial sources. The receiver system used a 30.5-cm diameter magnetic loop antenna mounted above the spacecraft on a stubby support. The plane of the loop antenna was maintained parallel to the earth's magnetic field lines, in order to receive magnetic wave components perpendicular to the field with a spectral density greater than 5.E-11 sq nT (sq gammas) per Hz. This experiment had three data outputs: (1) wideband (0.5 to 7.0 kHz) spectral information in analog form, (2) wideband (0.5 to 7.0 kHz) signal strength in digital form, and (3) 6 channels (0.7, 2.7, 4.3, 5.5, 7.0, and 8.8 kHz) of spectral data in digital form. The wideband analog data were mixed with the spacecraft digital data and transmitted to 16 ground-tracking stations in real time. Wideband signal strength was derived from the experiment automatic gain control (AGC) voltage, and provided a 40-dB dynamic range from 1.E-3 to 1.E-1 nT. These digital data were read out every 4 s. The onboard spectrum analyzer provided absolute amplitude information for the minimum amplitude from the six channels (50 Hz bandwidth). The amplitude data were obtained typically every 2 s over a dynamic range of 40 dB, ranging from 1.E-11 to 1.E-7 sq nT per Hz, with an additional two satellite-controlled attenuation steps of 20 dB each. Digital resolution was 2.5 dB. Both digital and analog data were recorded almost continuously from launch to spacecraft failure on October 28, 1963. More details about the VLF experiment construction, calibration, and operation are in D. A. Gurnett and B. J. O'Brien, J. Geophys. Res., v. 69, n. 1, p. 65, 1964.

Alternate Names

  • Injun3/VLFElectromagneticRadiation


  • Space Physics: Ionospheric Studies
  • Space Physics: Magnetospheric Studies

Additional Information

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



NameRoleOriginal AffiliationE-mail
Dr. Stanley D. ShawhanOther InvestigatorUniversity of Iowa
Dr. Brian J. O'BrienOther InvestigatorDepartment of Environmental
Prof. Donald A. GurnettPrincipal InvestigatorUniversity of Iowa
[] NASA Logo -