Explorer 39


Explorer 39
Mission typeEarth science
COSPAR ID1968-066A
SATCAT no.3337
Spacecraft properties
ManufacturerLangley Research Center
Launch mass9.4 kg (21 lb)
Start of mission
Launch date8 August 1968, 20:12 (1968-08-08UTC20:12) UTC[1]
RocketScout B S165C[1]
Launch siteVandenberg SLC-5
End of mission
Decay date22 June 1981 (1981-06-23)[2]
Orbital parameters
Reference systemGeocentric
RegimeLow Earth
Perigee altitude670 km (420 mi)[2]
Apogee altitude2,538 km (1,577 mi)[2]
Period118.2 minutes[2]
Epoch8 August 1968[2]

Explorer 39, also known as AD-C (Air Density C), was an American scientific satellite belonging to series Air Density. It was launched on August 8, 1968, join with Explorer 40, from Launch Complex 5 of the Vandenberg Air Force Base, through a Scout rocket.[2] Explorer 39 orbited the Earth once every 118.2 minutes, at an inclination of 80.6°. Its perigee was 680 kilometres (420 mi) and apogee was 2,522 kilometres (1,567 mi).[3]

Explorer 39 was an inflatable sphere, 3.6 m in diameter. It was orbited to make atmospheric density determinations. The satellite was successfully launched into a nearly polar, highly elliptical orbit. It was folded and carried into orbit, together with ejection and inflation equipment, as part of the payload of Explorer 40. Two density experiments were performed.[2]

One involved the study of systematic density variation, and the other was concerned with nonsystematic density changes. The upper atmospheric densities were derived from sequential observations of the sphere by use of an attached 136.62 MHz radio tracking beacon and by optical tracking. The radio beacon ceased transmitting in June 1971. Since that time it has been necessary to rely solely on the SAO Baker-Nunn camera network for tracking.[2]

Explorer 39 re-entered the atmosphere on June 22, 1981.[4]

See also


  1. ^ a b "Launch Log". Jonathan's Space Page. Retrieved June 10, 2018.
  2. ^ a b c d e f g h i j "AD-C". NSSDCA. NASA. Retrieved June 17, 2018. This article incorporates text from this source, which is in the public domain.
  3. ^ "ADE (Air Density Explorer)". David Darling. 2012. Retrieved 17 June 2018.
  4. ^ "EXPLORER 39 (ADI-3)". n2yo.com. 2011. Retrieved June 17, 2018.

External links