Interstation Rendezvous: The 1986 Mir–Salyut 7 Crew Transfer
Cosmonauts Leonid Kizim and Vladimir Solovyov conducted the only crewed transfer between two space stations, flying from Mir to Salyut 7 in 1986, spending 50 days there, and returning with 350–400 kg of instruments after a 29-hour transfer each way, for a total mission of 125 days.