222 



GEODETIC EXPLORERS 



EXPLORERS 29 (launched 1965) and 36 (1968). 



IONOSPHERIC EXPLORERS 



Four U.S. [EXPLORERS 8 (1960), 20 (1964), 22 (1964), and 27 

 (1965)] and nine International satellites [U.K. -U.S.: ARIEL 1 

 (1962) and ARIEL 4 (1971); U.S. -Canada: ALOUETTE 1 (1962), ISIS-X 

 (1965), ISIS A (1969), and ISIS B (1971); U.S. -France: FR-1 

 (1968); and the European Space Agency (ESA) : ESRO I (1969) and 

 ESRO IB (1969)] were designed to determine the nature, dynamic 

 behavior, and distribution of changed particles, electrons, and 

 ions as observed from above the ionosphere. 



MAGNETOSPHERE EXPLORERS 



General: EXPLORERS 6 (1959) and 10 (1961) were designed to 

 measure radiation levels in space. EXPLORER 45 (1971) was designed 

 to measure ring currents and magnetic storms. 



In jun-Hawkeye : EXPLORERS 25 (1964) and 40 (1968) were de- 

 signed to measure the radiation of atomic ions into the Earth's 

 atmosphere. EXPLORER 52 (1974) was designed to measure the solar 

 wind and magnetic field interactions in the polar regions of the 

 Earth. 



Interplanetary Monitoring Platforms (IMPs): Ten missions 

 [EXPLORERS 18 (1963), 21 (1964), 28 (1965), 34 (1966), 34 (1967), 

 35 (1967), 41 (1969), 43 (1971), 47 (1972), and 50 (1973)] were 

 designed to study interplanetary magnetic fields between the 

 Earth and the Moon. [1984 $$ : $80 million] 



International Sun-Earth EXPLORERS (ISEE): U.S.: ISEE 1 

 (1977); U.S.-E.S.A.: ISEE 2 (1977) and ISEE 3 (1978). ISEE 2 

 had Swedish instruments and ISEE 3 had Swedish, Dutch, and British 

 instruments. These satellites were designed to study the solar- 

 terrestrial relationships at the outermost boundary of the mag- 

 netosphere. [1984 $$ : $60 million] 



Dynamics EXPLORER A/B: Launched in August 1981 to image the 

 polar caps. It continues to investigate the plasma of the mag- 

 netosphere. [1984 $$ : $52.9 million] 



Active Magnetospheric Particle Trace EXPLORERS (AMPTE): 

 Launched on August 16, 1984, to study entry windows, entry 

 mechanisms, energization, and transport of energetic particles in 

 magnetospheric radiation. International participation in the 

 program includes the Federal Republic of Germany (spacecraft and 

 experiments), United States (spacecraft, experiments, launch 

 site, and operations), and the U.K. (extreme ultraviolet camera). 



SOLAR-PHYSICS EXPLORERS 



EXPLOPvERS 7 (1959), 20 (1964), 37 (1968), and 44 (1971) were 

 designed to monitor solar x-rays and solar radiation. 



