Venera-5 Automated Interplanetary Station delivered a descent module into the atmosphere of Venus.
The Venera-5 Automated Interplanetary Station was a further development of the Venera-4 program. Following the results of the flight of Venera-4 the orbiter remained virtually unchanged (only the SG 59M magnetometer was removed), but the descent module was significantly redesigned.
Basing on the data obtained from the Venera-4 descent module, the model of the Venus atmosphere was revised. Therefore, the Venera-5 descent module was designed for the external pressure of 25 atmospheres and the temperature of 290±10°С at the planet's surface, versus 10 atmospheres and 425°С in the previous model, respectively.
All the above forced a significant increase in the strength of the DM design by increasing the thickness of the walls. In addition, the gas pressure inside the descent module was improved to increase its rigidity from 2 to 2.5 atmospheres. At the same time, the mass of the DM was increased by 33 kgs. In order to keep up with the capabilities of the Molniya-M launch vehicle and the VL upper stage, the mass of the orbiter was reduced by 14 kgs due to removal of the magnetometer.
The increase of the estimated atmospheric pressure also allowed to decrease the sizes of the domes of the brake and the main parachutes - 1.9 instead of 2.2 m² and 12 instead of 55 m² respectively, which should have led to decrease of the descent time in the atmosphere before the DM touchdown to the surface of the planet. The parachute dome was made of a special heat-resistant fabric, preserving its operability at the ambient temperatures exceeding 500°С.
Due to the unstable operation of the «Venera-4» radio altimeter, a modified radio altimeter was installed on the Venera-5 descent module.
The composition of the scientific equipment of the descent module was also changed. As for Venera-4, the landing area was chosen on the night side of the planet.