Explorer 13


Explorer 13
Explorer 13 (S-55A)
Harvard designation1961 χ1
COSPAR ID1961-022A
SATCAT no.180
Mission duration3 days
Spacecraft properties
Launch mass86 kg (190 lb)
Start of mission
Launch dateAugust 25, 1961, 19:26 (1961-08-25UTC19:26) UTC[2]
RocketScout X-1
Launch siteWallops LA-3
End of mission
Last contactAugust 28, 1961 (1961-08-29)
Orbital parameters
Reference systemGeocentric
RegimeLow Earth
Perigee altitude125 km (78 mi)[1]
Apogee altitude1,164 km (723 mi)[1]
Period97.5 minutes[1]
EpochAugust 25, 1961[1]

Explorer 13 (also called S-55A) was an American satellite launched as part of the Explorers program on August 25, 1961 from Wallops Flight Facility, Virginia, U.S.

Weighing 187 pounds, including its fourth stage and transition section, its objective was to test the performance of a scout vehicle and its guidance system and to investigate the nature and effects of space flight on micrometeoroids. Its payload was a 76 inches x 24-inch cylinder, almost covered by five types of micometeoroid impact detectors, two transmitters, solar cells and nickel cadmium batteries. Its orbit was lower than planned and the satellite re-entered on August 27,1961.

Its Orbital Elements: Apogee 722 statute miles; Perigee 74 statute miles; Orbital Period 97.5 minutes.[3]


Explorer 13 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 cadmium sulfide-cell, wire-grid, piezoelectric, pressurized-cell, and foil-type micrometeoroid detectors.

The spacecraft was a 1.93 m × 0.61 m (6.3 ft × 2.0 ft) 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.


  1. ^ a b c d e f g "S 55A". NSSDC Master Catalog. NASA Goddard Space Flight Center. This article incorporates text from this source, which is in the public domain.
  2. ^ "Jonathan's Space Page".
  3. ^ As of July 1962 - Goddard Space Flight Center / NASA * Profile of a satellite