Explorer 50 (IMP-8).
|Mission type||Magnetospheric research|
|Mission duration||33 years|
|Manufacturer||Goddard Space Flight Center|
|Launch mass||900 lb (410 kg)|
|Dry mass||818 lb (371 kg)|
|Dimensions||Polyhedron of 16 faces|
157.4 cm (62.0 in) height
135.6 cm (53.4 in) diameter
|Start of mission|
|Launch date||26 October 1973, 02:26:03UTC|
|Rocket||Delta 1604 582/D97|
|Launch site||Cape Canaveral LC-17B|
|End of mission|
|Last contact||7 October 2006|
|Perigee altitude||141,185 km (87,728 mi)|
|Apogee altitude||288,857 km (179,487 mi)|
|Epoch||29 October 1973|
Explorer 50 was launched on 23 October 1973 at 02:26:03 UTC, by a Delta 1604 rocket from Cape Canaveral AFS, Florida. The spacecraft functioned nominally until 7 October 2006. The satellite orbited the Earth once every 12 days, at an inclination of 28.6 degrees. Its perigee was 22 earth radii and apogee was 45 earth radii.
Explorer 50 was a drum-shaped spacecraft, 135.6 centimetres (53.4 in) across and 157.4 centimetres (62.0 in) height, with propulsion Star-17A, instrumented for interplanetary and magnetotail studies of cosmic rays, energetic solar particles, plasma, and electric and magnetic fields. Its initial orbit was more elliptical than intended, with apogee and perigee distances of about 45 earth radii and 25 earth radii. Its eccentricity decreased after launch. Its orbital inclination varied between 0° and about 55° with a periodicity of several years. The spacecraft spin axis was normal to the ecliptic plane, and the spin rate was 22.3 rpm. The data telemetry rate was 1600 bps. The spacecraft was in the solar wind for 7 to 8 days of every 12 days orbit.
Telemetry coverage was 90% in the early years, but only 60-70% through most of the 1980s and early 1990s. Coverage returned to the 90% range in the mid to late 1990s. The objectives of the extended Explorer 50 operations were to provide solar wind parameters as input for magnetospheric studies and as a 1 AU baseline for deep space studies, and to continue solar cycle variation studies with a single set of well-calibrated and understood instruments. In October, 2001, Explorer 50 was terminated as an independent mission. The last useful science data from Explorer 50 was acquired on 7 October 2006.
PLA (Plasma Faraday Cup Assembly). The objective is to study the positive ions and electrons in the solar wind, transition region, and magnetotail. Parameters derived on a routine basis are proton velocity, number density, and temperature.
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