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Explorer: BE A, B, C

Explorer 27 (BE B) [NASA]

The BE (Beacon Explorer) satellites provided Laser reflectors for geodetic measurements as well measured the electron density in the ionosphere. The main purpose of this satellite is to record observations of electron content between the earth and the satellite worldwide. Other duties include using a three-axis magnetometer and sun sensors to determine satellite spin rate and attitude data. Information could only be connected when the satellite was in range of a ground telemetry station, because it did not have a tape recorder. Initially, the Beacon-C was spin stabilized; however, after the solar paddles were erected, the satellite was despun. A strong bar magnet and damping rods were used to align the satellite axis of symmetry with the local magnetic field. Transmitters operated at 162 and 324 MHz and were turned off on 20 July 1973 because these frequencies interfered with more important spacecraft.

SLR (Space Laser Reflector) data from Beacon-C is used to monitor the secular and long period tidal variations in the Earth's gravity field. SLR provides a critical global constraint on the geophysical modeling to improve our understanding of the rheology of Earth, such as the mantle viscosity and anelasticity, and the postglacial rebound since the last ice age.

Instrumentation: BEACON-C has the following instrumentation onboard:

  • Radio Beacons
  • Doppler Navigation System
  • Electrostatic Probe
  • Passive Laser Tracking Reflector consisting of 160 cube corners.
Nation: USA
Type / Application: Geodesy, Ionospheric research
Operator: NASA
Contractors: Johns Hopkins University Applied Physics Laboratory (APL)
Equipment: Radio Beacons, Doppler Navigation System, Electrostatic Probe, Passive Laser Tracking Reflector
Configuration: Transit-Bus
Propulsion: ?
Power: 4 deployable solar arrays, batteries
Mass: 120 kg (#A); 53 kg (#B); 60 kg (#C)
Orbit: 886 km × 1079 km, 79.69 (#B); 936 km × 1316 km, 41.18 (#C)
Satellite COSPAR Date LS Launch Vehicle Remarks
Explorer (20) (BE A, S 66) 1964-F02 19.03.1964 CC LC-17A F Delta-B
Explorer 22 (BE B, S 66a) 1964-064A 10.10.1964 Va PALC-D Scout-X4
Explorer 27 (BE C) 1965-032A 29.04.1965 Va PALC-D Scout-X4


Further Explorer missions: