It incorporated a re-entry body (capsule) for landing scientific instruments and test objects. It was a biological satellite that made a sustained biomedical experiment with the dogs Veterok and Ugolyok, after 22 days in orbit around the Earth, they were safely landed.
This spaceflight of record-breaking duration was not surpassed by humans until Skylab 2 in June 1973 and still stands as the longest space flight by dogs.
Payloads are separated by bullets ( · ), launches by pipes ( | ). Manned flights are indicated in bold text. Uncatalogued launch failures are listed in italics. Payloads deployed from other spacecraft are denoted in brackets.