Two pairs of early Soviet scientific spacecraft, launched in 1964, which
observed Earth's inner and outer radiation belts, cosmic rays, and the upper
atmosphere. One of each pair (Elektrons 1 and 3) were placed in a lower
orbit to take measurements of the inner Van
Allen belt; the other of each pair (Elektrons 2 and 4) were placed in
a higher orbit to study the outer Van Allen belt.
| Elektron 2
AND SPACE PROBES