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S 55A



Explorer 13 (S-55A) was injected into a geocentric orbit of moderate eccentricity using a Scout launch vehicle. The objectives of the flight were to test vehicle performance and guidance and to investigate the nature and effects of micrometeoroids on the spacecraft systems. The scientific instrumentation consisted of cadium sulfide-cell, wire-grid, piezoelectric, pressurized-cell, and foil-type micrometeoroid detectors. The spacecraft was a 1.93-m-long, 61-cm-diameter cylinder. The orbit was lower than planned, and the spacecraft reentered the atmosphere on August 28, 1961, after only slightly more than 2 days in orbit. No penetrations were recorded by this satellite during experiment operations. This aided in determination of useful flux limits for subsequent experiment design.

The S-55A satellite was the fourth Altair stage of the launch vehicle. It had a diameter of 61 cm (24 in.), a length of 193 cm (76 in.), and a mass of 85 kg (187 lbs.). Four whip antennas extended from the nose section, and two separate telemetry transmitters, at 136.86 and 136.20 MHz could be turned on for a minute at a time by ground command. At these times it would read out from a data storage unit. A beacon also operated continuously at 136.86 MHz, powered by mercury batteries. Power was supplied by solar cells mounted on the side of the nose section, charging nickel-cadmium batteries.

The payload consisted of six experiments. The first comprised 160 half-cylinder cells, pressurized with nitrogen and made of varying thickness of beryllium-copper. The second had 60 triangular foil gauge detectors mounted under stainless steel skins. The third had 46 copper wire grids wound on melamine cards. The fourth consisted of two cadmium-sulfide cells mounted in aluminized glass flasks. Piezoelectric crystal impact transducers made up the fifth experiment, and the sixth had five groups of p-on-n solar cells with various protective coverings.

Alternate Names

  • 00180
  • 1961 Chi 1
  • Explorer 13
  • S55A

Facts in Brief

Launch Date: 1961-08-25
Launch Vehicle: Scout
Launch Site: Wallops Island, United States
Mass: 85 kg

Funding Agency

  • NASA-Office of Aeronautics and Space Technology (United States)


  • Planetary Science

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Mr. Charles T. d'AiutoloProject ManagerUnknown

Selected References

  • D'Aiutolo, C. T., Micrometeoroid satellite Explorer 13 (1961 Chi), NASA, TN D-2468, Wash., D.C., Nov. 1964.
  • Micrometeoroid satellite S-55, NASA, N-90,006, Wash., D.C., June 1961.
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