into the Venusian atmosphere, the heat shield temperature rose to and at one point the cabin deceleration reached 300 G. The descent lasted 93 minutes. The capsule deployed its parachute at an altitude of about , and started sending data on pressure, temperature and gas composition back to Earth. The temperature control kept the inside of the capsule at . The temperature at was recorded as , and the pressure as less than . At the end of the descent, the temperature reached and pressure increased to , 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. Radar altimeter The altitude of the Venera probe relative to the surface was measured using a radar altimeter operating at 770 MHz. The altimeter had an integer ambiguity of : that is, the same radar signal would be given at an altitude of X, X plus , X plus , etc. (an effect known as "aliasing"). At the time the distance of the cloud tops above the surface was not known, and due to this ambiguity, the first radar return, now believed to be at an actual altitude of about , was initially misinterpreted as . Therefore, based on the misinterpreted radar results, the Soviet team initially announced the probe descended to the surface. This result was quickly dismissed as inconsistent with the planetary diameter measured by radar, and the pressure readings by the capsule were much lower than predicted by the recently developed models of the Venus atmosphere. Analysis The Venera 4 data was analysed together with the data of the Mariner 5 probe, under a combined Soviet–American working group of COSPAR in 1969, an organization of early space cooperation, allowing a more complete drawing of the profile of the atmosphere of Venus. Achievements For the first time, in situ 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 measured ratio of carbon dioxide to nitrogen of about 13 corrected the previous estimates so much (an inverse ratio was expected in some quarters) that some scientists contested the observations. The main station detected no radiation belts; relative to Earth, the measured magnetic field was 3000 times weaker, and the hydrogen corona was 1000 times less dense. No atomic oxygen was detected. All the