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 through the Van Allen radiation belts 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 Soyuz 11 in June 1971 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.