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On February 12, 1961, 00:34:36 UTC, the first planetary probe was launched to Venus by the Soviet Union. The Venus-1 Automatic Interplanetary Station, or Venera 1, was a 643.5 kg probe consisting of a cylindrical body 1.05 meter in diameter topped by a dome, totaling 2.035 meters in height. This was pressurized to 1.2 atmospheres of dry nitrogen, with internal fans to maintain even distribution of heat. Two solar panels extended from the cylinder, charging a bank of silver-zinc batteries. A 2 meter parabolic wire-mesh antenna was designed to send data from Venus to Earth on 922.8 MHz. A 2.4 meter antenna boom was used to transmit short-wave signals during the near-Earth phase of the mission. Semidirectional quadrapole antennas mounted on the solar panels provided routine telemetry and telecommand contact with Earth during the mission, on a circularly-polarized decimeter radio band.
The probe was equipped with scientific instruments including a flux-gate magnetometer attached to the antenna boom, two ion traps to measure solar wind, micrometeorite detectors, and Geiger counter tubes and a Sodium Iodide scintillator for measurement of cosmic radiation. An experiment attached to one solar panel measured temperatures of experimental coatings. Infrared and/or ultraviolet radiometers may have been included. The dome contained a KDU-414 engine used for mid-course corrections. Temperature control was achieved by motorized thermal shutters.
Soviet experts launched Venera-1 in two steps, first placing the 7-ton Sputnik 8 into terrestrial parking orbit with a Molniya launcher. From a 229 × 282 km orbit, the automatic interplanetary station was launched towards Venus with a fourth stage engine. This was the first demonstration of the highly efficient maneuver of launching from orbit. The 11D33 engine was the world's first staged-combustion-cycle rocket engine, and also the first use of a ullage engine to allow a liquid-fuel rocket to start under weightlessness.
Three successful telemetry sessions were conducted, gathering solar-wind and cosmic-ray data near Earth, at the Earth's magnetopause, and on February 19 at a distance of 1,900,000 km. After discovering the solar wind with Luna-2, Venera-1 provided the first verification that this plasma was uniformly present in deep space. Seven days later, the next scheduled telemetry session failed to occur. On May 19 and 20, 1961, Venera 1 passed within 100,000 km of Venus and entered a heliocentric orbit. With the help of the British radio telescope at Jodrell Bank, some weak signals from Venera-1 may have been detected in June. Soviet engineers believe that Venera-1 failed due to the overheating of a solar-direction sensor.
Venera-1 was an important milestone in spacecraft design -- the first truly modern planetary probe. During most of its flight, it was spin stabilized. It was the first spacecraft designed to perform mid-course corrections, by entering a mode of 3-axis stabilization, fixing on the Sun and the star Canopus. Had it reached Venus, it would have entered another mode of 3-axis stabilization, fixing on the Sun and Earth, and using for the first time a parabolic antenna to relay data.
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