“EnVision as currently conceived cannot take place without this lengthy phase of aerobraking,” said EnVision study manager Thomas Voirin. “The spacecraft will be injected into Venus orbit at a very high altitude, at approximately 250,000 km, then we need to get down to a 500 km altitude polar orbit for science operations. Flying on an Ariane 62, we cannot afford all the extra propellant it would take to lower our orbit.
However, this won’t be the first time a spacecraft has used aerobraking at Venus. ESA’s Venus Express, performed experimental aerobraking during the final months of its mission in 2014, gathering valuable data on the technique. The Venus Express mission was supposed to last 500 days, but the robust spacecraft ultimately spent eight years orbiting Venus before running out of fuel.
This is a phenomenon that remained unknown during the first decades of the space age. It was only when early Space Shuttle flights returned from low orbit in the early 1980s that engineers received a shock: the spacecraft’s thermal blankets had been severely eroded. Space Shuttle Endeavour’s tail aglow with atomic oxygen, as seen during the STS-99 mission in February 2000. Highly erosive atomic oxygen turned out to eat away at unprotected thermal blankets during early Shuttle missions, until countermeasures were put in place. Credit: NASA