Explorer 17


Explorer 17
Ae-a explorer-17.jpg
Mission typeEarth science
COSPAR ID1963-009A
SATCAT no.564
Mission duration1,325 days
Spacecraft properties
Launch mass185 kilograms (408 lb)
Start of mission
Launch dateApril 3, 1963, 02:00:02 (1963-04-03UTC02:00:02Z) UTC
RocketDelta B
Launch siteCape Canaveral LC-17A
End of mission
Last contactJuly 10, 1963 (1963-07-11)
Decay date24 November 1966, 09:45:32 UTC
Orbital parameters
Reference systemGeocentric
RegimeLow Earth
Semi-major axis6,963.64 kilometers (4,327.01 mi)
Perigee altitude255 kilometers (158 mi)
Apogee altitude916 kilometers (569 mi)
Period96.39 minutes
RAAN347.3897 degrees
Argument of perigee125.5060 degrees
Mean anomaly234.7807 degrees
Mean motion16.38971129
Epoch10 July 1963
Revolution no.20364
Pressure gauges
mass spectrometers
electrostatic probes

Explorer 17 (also known as Atmosphere Explorer-A (AE-A) and S6) was a United States satellite, launched at Cape Canaveral from LC-17B on a Delta-B booster, on April 3, 1963, to study the Earth's upper atmosphere. It was the first satellite of five Atmosphere Explorers.

Technical specifications

Explorer 17 was a spin-stabilized sphere 0.95 m in diameter. The spacecraft was vacuum sealed in order to prevent contamination of the local atmosphere. Explorer 17 carried four pressure gauges for the measurement of total neutral particle density, two mass spectrometers for the measurement of certain neutral particle concentrations, and two electrostatic probes for ion concentration and electron temperature measurements. Battery power failed on July 10, 1963. Three of the four pressure gauges and both electrostatic probes operated normally. One spectrometer malfunctioned, and the other operated intermittently.

The successful launch and operating of Explorer 17 allowed scientists for the first time to obtain instantaneous atmospheric density measurements using several independent measuring systems, to measure the atmosphere during a single day under nearly constant local time conditions and geomagnetic activity, and to compare direct measurements of density with those inferred from measurements of perturbations in the satellite period orbit.[1]

The spacecraft decayed from orbit after 1,325 days on November 24, 1966.


  1. ^ Newton, George P.; Horowitz, Richard; Priester, Wolfgang (July 1965). "Atmospheric Density and Temperature Variations from the Explorer XVII Satellite and a Further Comparison with Satellite Drag". Planetary and Space Science. 13 (7): 599–616. Bibcode:1965P&SS...13..599N. doi:10.1016/0032-0633(65)90042-5.

External links

  • NASA's Explorer Missions
  • Gunter's Space Page - information on Explorer 17
  • Space History Notes