Venera 4

Launch data: Designation 02840 / 67058A Launch date 12 Jun 1967 - 02:40 UT Launch site Baikonur Launch vehicle Molniya-M (8K78M) Mission Venus lander Satellite type  4V-1 n°310

Specifications: Prime contractor  Lavochkin Operator   Mass at launch  1104 kg Dry Mass   Base probe: Basic shape - Dimension  high= 3.5m Solar array  4 solar panels with an area of 2.5 m² Landing capsule: Basic shape  sphere Dimension  dia= 1m Dry Mass  383 kg Decay: Venus impact:  18 Oct 1967 Lifetime:  128,14 days

Venera 4 Venera 4 lander

Description:

• The main hub of Venera 4 stood 3.5 meters high, its solar panels spanned 4 meters and had an area of 2.5 m². The hub included a 2 meter long magnetometer, an ion detector, a cosmic ray detector and an ultraviolet spectrometer capable of detecting hydrogen and oxygen gases. The devices were intended to operate until entry into the Venusian atmosphere. At that juncture, the station was designed to release the probe capsule and disintegrate. The rear part of the hub contained a liquid-fuel thruster capable of correcting the flight course. The flight program was planned to include two significant course corrections, for which purpose the station could receive and execute up to 127 different commands sent from the Earth.
• The front part of the hub contained a nearly spherical landing capsule 1 meter in diameter and weighing 383 kg. Compared to previous (failed) Venera probes, the capsule contained an improved heat shield which could withstand temperatures up to 11000 °C. Instead of the previous liquid-based cooling design, a simpler and more reliable gas system was installed. The durability of the capsule was checked by exposing it to high temperatures, pressures and accelerations using three unique testing installations. The heat resistance was checked in a high-temperature vacuum system emulating the upper layers of the atmosphere. The capsule was also pressurized up to 100 atmospheres (the surface pressure on Venus was thought to be 72 atm). Finally, it was subjected to accelerations of up to 450 G in a centrifuge. The centrifuge test caused cracking of electronic components and cable brackets, which were all replaced shortly before launch. The timing for launch was rather tight, so as not to miss the "launch window" - the days of the year when the path to the destination planet from Earth is energetically least demanding.
• The capsule could float in case of a water landing. Considering the possibility of such a landing, its designers made the lock of the capsule using sugar; it was meant to dissolve in liquid water, releasing the transmitter antennas. The capsule contained a newly developed vibration-damping system and its parachute could resist temperatures up to 450 °C.
• The capsule contained an altimeter, thermal control, a parachute and equipment for making atmospheric measurements. The latter included a thermometer, barometer, hydrometer, altimeter and a set of gas analysis instruments. The data were sent by two transmitters at a frequency of 922 MHz and a rate of 1 bit/s; the measurements were sent every 48 seconds. The transmitters were activated by the parachute deployment as soon as the outside pressure increased to 0.6 atmospheres, which was thought to occur at the altitude about 26 km above the surface of Venus. The signals were received by several stations, including the Jodrell Bank Observatory.
• The capsule was equipped with a rechargeable battery with a capacity sufficient for 100 minutes of powering the measurement and transmitter systems. To avoid becoming discharged during the flight to Venus, the battery was recharged using the solar panels of the hub. Before the launch, the entire Venera 4 station was sterilized to prevent possible biological contamination of Venus.

Mission details:

• Two nominally identical Venera 4-type probes were launched in June 1967. The first probe, Venera 4, was launched on 12 June from a Tyazheliy Sputnik (67-058B). A course correction was performed on 29 July when it was 12 million km away from Earth; otherwise the probe would have missed Venus. Although two such corrections had been planned, the first one was accurate enough and therefore the second correction was canceled. On October 18, 1967, the spacecraft entered the Venusian atmosphere with an estimated landing place near 19°N 38°E? / ?19°N 38°E? / 19; 38.
• The second, launched on 17 June, experienced a failure of one of its rocket stages and only managed to reach Earth orbit, reentering the Earth's atmosphere 8 days later. This probe was renamed Cosmos 167.
• During entry into the Venusian atmosphere, the surface temperature rose to 11000 °C and at one point the cabin acceleration reached 300 G. The descent lasted 93 minutes. The capsule deployed its parachute at an altitude of about 52 km, and started sending data on pressure, temperature and gas composition back to Earth. The temperature control kept the inside of the capsule at -8 °C. The temperature at 52 km was recorded as 33 °C, and the pressure as less than 1 atm. At the end of the 26-km descent, the temperature reached 262 °C and pressure increased to 22 atmospheres, and the signal transmission terminated. The atmospheric composition was measured as 90-93% carbon dioxide, 0.4-0.8% oxygen, 7% nitrogen and 0.1-1.6% water vapor.
• Misbehavior of the altimeter resulted in the value of initial altitude (deployment of the capsule's parachute and start of the measurements) being transmitted as 26 km. Therefore, some Earth observers interpreted the descent as having continued to the surface of Venus, which was quickly dismissed as inconsistent with other data. In particular, the pressure readings by the capsule were much too low for the Venusian surface
• For the first time, analysis of the atmosphere of another planet was performed and the data sent back to Earth; the analysis included chemical composition, temperature and pressure.
• The mission was considered a complete success, especially given several previous failures of Venera probes. Although the Venera 4 design did allow for data transmission after landing, the Venera 3-6 probes were not built to withstand the pressures at the Venusian surface. The first successful landing on Venus was achieved by Venera 7 in 1970.