Explorer 18

USA

Interplanetary Monitoring Probe, also called IMP 1 (or IMP-A)

Launch data:

Designation	00693 / 63046A
Launch date	27 Nov 1963 - 02:30 UT
Launch site	CC, LC17B
Launch vehicle	Delta-B (#387/D21)
Mission	Scientific: magnetosphere study
Perigee/Apogee	192/197616 km
Inclination	33.3°
Period	5666.2 min
Dry mass on-orbit	138 kg

Description

Explorer 18 (IMP 1) was a solar-cell and chemical-battery powered spacecraft instrumented for interplanetary and distant magnetospheric studies of energetic particles, cosmic rays, magnetic fields, and plasmas. Initial spacecraft parameters included a local time of apogee of 1020 h, a spin rate of 22 rpm, and a spin direction of 115 deg right ascension and -25 deg declination. Each normal telemetry sequence of 81.9 s duration consisted of 795 data bits. After every third normal sequence there was an 81.9-s interval of rubidium vapor magnetometer analog data transmission. The spacecraft performed normally until May 30, 1964, then intermittently until May 10, 1965, when it was abandoned. The principal periods of data coverage were November 27, 1963 to May 30, 1964; September 17, 1964 to January 7, 1965; and February 21, 1965 to March 25, 1965; however, only the first of these periods was very useful.

End of life

Decay

30 Dec 1965

Ref.: #1, #7, #14, #15, #27 - update: 12.07.04

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