Sputnik 7 was the first Soviet attempt at launching prode to explore Venus. The probe was successfully launched into Earth orbit with a SL-6/A-2-e launcher. The launch payload consisted of an Earth orbiting launch platform (Tyazheliy Sputnik 4 ) and the Venera probe . The fourth stage (a Zond rocket ) was supposed to launch the Venera probe towards a landing on Venus after one Earth orbit but ignition failed, probably due to a faulty timer, and the spacecraft remained in Earth orbit. Because of its large size (6483 kg), the mission was originally thought by non-Soviet observers to be a failed manned mission, and later was described as a test of an Earth orbiting platform from which an interplanetary probe could be launched.