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S 55C



The Explorer 23 micrometeoroid satellite was the third in the series of S 55 micrometeoroid satellites orbited by NASA. Its purpose was to obtain data on the near-earth meteoroid environment, thus providing an accurate estimate of the probability of penetration in spacecraft structures by meteoroids and allowing a more confident definition of the penetration flux-material thickness relation to be derived. It was also a test of the Scout rocket system's reaction to high air loads, having been purposely launched to encounter winds of 70 mph or higher at 25,000 to 40,000 feet altitude.

The cylindrically shaped spacecraft, about 61 cm in diameter and 234 cm long, was built around the burned out Altair II fourth stage of the Scout launch vehicle, which remained as part of the orbiting satellite. Explorer 23 carried stainless steel pressurized-cell penetration detectors, impact detectors, and cadmium sulfide cell detectors to obtain data on the size, number, distribution, and momentum of dust particles in the near-earth environment. In addition, the spacecraft was designed to provide data on the effects of the space environment on the operation of capacitor penetration detectors and solar-cell power supplies, and carried two groups of n-on-p solar cells, one unshielded and one with a 2 cm (3/16 in) quartz cover. The spacecraft mass, neglecting the fourth stage vehicle hardware and motor, was 96.4 kg. Power was supplied by solar cells charging nickel-cadmium batteries. Telemetry systems operated at 136.08 and 136.86 MHz. A timing device was set to cut off transmissions after one year.

Explorer 23 launched from Wallops Island on 6 November 1964 and entered a 451 x 865 km orbit with an inclination of 51.9 degrees. The spacecraft was spin-stabilized and operated satisfactorily during its 1 year life (November 6, 1964, through November 7, 1965). All mission objectives were accomplished, except for the cadmium sulfide cell detector experiment, which was damaged on liftoff and provided no data.

Alternate Names

  • 00924
  • Explorer 23
  • S55C

Facts in Brief

Launch Date: 1964-11-06
Launch Vehicle: Scout
Launch Site: Wallops Island, United States
Mass: 133.8 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

Selected References

  • Naumann, R. J., The near-earth meteoroid environment, NASA-MSFC, TN D-3717, Huntsville, Ala., Nov. 1966.
  • O'Neal, R. L., Explorer XXIII micrometeoroid satellite description and results for the period, NASA, TN D-4284, Wash., D.C., June 1968.
  • D'Aiutolo, C. T., et al., Recent NASA meteoroid penetration results from satellities, in NASA, SP-135, Wash., D.C. and Smithsonian Contrib. Astrophys., 11, 239-252, 1967.
  • Explorer 23 micrometeoroid satellite - description and preliminary results for the period November 6, 1964 through February 15, 1965, NASA, TM-X-1123, Washington, DC, Aug. 1965.
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