Explorer 24


Explorer 24
Explorer 24.jpg
Explorer 24.
Mission typeEarth science
COSPAR ID1964-076A[1]
SATCAT no.931
Mission duration1,426 days[2]
Spacecraft properties
BusADE bus
ManufacturerLangley Research Center
Launch mass8.6 kg (19 lb)
Start of mission
Launch date21 November 1964, 17:09:39 (1964-11-21UTC17:09:39) UTC[3][4]
RocketScout X-4[5]
Launch siteVandenberg SLC-5[5]
End of mission
Decay date18 October 1968 (1968-10-19)[1]
Orbital parameters
Reference systemGeocentric
RegimeLow Earth
Perigee altitude525 km (326 mi)[1]
Apogee altitude2,498 km (1,552 mi)[1]
Period116.3 minutes[1]
Epoch21 November 1964[1]
Nonsystematic Changes of Air Density
Systematic Changes of Air Density

Explorer 24 (also called AD-B and S-56C) was a U.S. satellite designed for atmospheric studies. Explorer 24 was launched on 21 November 1964 from Vandenberg Air Force Base, Lompoc, California, with a Scout rocket. Explorer 24 was launched along with its successor satellite, Explorer 25.


Explorer 24 was placed in orbit together with Explorer 25 from a single launch vehicle. Explorer 24 was identical in configuration to the previously launched balloon satellites Explorer 9 and 19. The spacecraft was 3.6 m in diameter, was built of alternating layers of aluminum foil and plastic film, and was covered uniformly with 5.1-cm white dots for thermal control.

It was designed to yield atmospheric density near perigee as a function of space and time from sequential observations of the sphere's position in orbit. To facilitate ground tracking, the satellite carried a 136 MHz tracking beacon.

The satellite reentered the earth's atmosphere on October 18, 1968.[1]


Explorer 24 helped determine the variation in density between the day and night of the Earth and gave rise to studies on the zone winds in the exosphere, at an altitude of between 450 kilometres (280 mi) and 620 kilometres (390 mi).[6][7]


  1. ^ a b c d e f g h i "S 55C". NSSDC Master Catalog. NASA Goddard Space Flight Center. Retrieved 10 June 2018. Public Domain This article incorporates text from this source, which is in the public domain.
  2. ^ "1964-076A - Explorer 24". Space 40 (in Czech). Lubor Lejček, Antonín Vítek. Retrieved 10 June 2018.
  3. ^ "Launch Log". Jonathan's Space Page. Retrieved June 10, 2018.
  4. ^ "Letter dated 5 February 1965 from the Permanent Representative of the United States of America addressed to the Secretary-General" (PDF). COMMITTEE ON THE PEACEFUL USES OF OUTER SPACE. UNOOSA. November 30, 1964. Archived from the original on 5 May 2018. Retrieved 10 June 2018.
  5. ^ a b "Explorer". Encyclopedia Astronautica. Mark Wade. Retrieved 10 June 2018.
  6. ^ Jacchia, L. G.; Slowey, J. (1966). "The Shape and Location of the Diurnal Bulge in the Upper Atmosphere". SAO Special Report (207). Jacchia, L. G. & Slowey, J. 207. Bibcode:1966SAOSR.207.....J.
  7. ^ Blum, P. W.; Schuchardt, K. G. H. (June 24, 1976). "Exospheric zonal winds between 540 and 620 km from the orbit of Explorer 24". Planetary and Space Science 24: 529–539. Blum, P. W.; Schuchardt, K. G. H. 24 (6): 529. Bibcode:1976P&SS...24..529B. doi:10.1016/0032-0633(76)90131-8.