Efir was a series of Soviet scientific spacecraft based on the Vostok/Zenit design; "Efir" is Russian for "ether". They were used to measure the energy spectrum and charge composition of primary cosmic rays with energy above 2 TeV. The Efirs were announced under the catchall Cosmos designation.
|spacecraft||launch date||launch vehicle||site||orbit||duration||mass|
|Cosmos 1543||Mar 10, 1984||Soyuz-U||Plesetsk||214 × 401 km × 62.8°||26 days||6,300 kg|
|Cosmos 1713||Dec 27, 1985||Soyuz-U||Plesetsk||215 × 397 km × 62.8°||26 days||6,300 kg|