Helios-1
Parameters
12/16/1974 - 6/30/1977
07/01/1977 - 12/31/1978
01/01/1979 - 12/31/1980
01/01/1981 - 12/31/1982
Helios-2
Parameters
01/19/1976 - 06/06/1977
07/01/1977 - 12/31/1978
01/01/1979 - 12/23/1979