Only one space mission has gone to Venus in the last 30 years. NASA and the European Space Agency are going to launch three new missions to Venus by the early 20th century.

The EnVision mission will take pictures of the planet's surface. To slow down and lower its altitude through the planet's hot, thick atmosphere, a special maneuver is needed. Aerobraking and EnVision will take about two years to complete.

There is a necessity for the maneuver.

Thomas Voirin said that EnVision cannot take place without this lengthy phase of Aerobraking. We need to get down to a 500 km altitude polar circle for science operations after injecting the spacecraft into Venus. We can't afford all the extra fuel it would take to get us to our destination. We will pass through the upper atmosphere of Venus, coming as low as 130 km from the surface.

Aerobraking has been done by several Mars craft to slow them down and place them in the correct location. The European Space Agency said that they are testing candidate materials to make sure they can survive the atmospheric surfing on Venus.

This won't be the first time a craft has flown at Venus. During the final months of its mission, the Venus Express collected valuable data on the technique. The Venus Express mission was supposed to last 500 days, but it only lasted eight years due to lack of fuel. It began a controlled descent, dipping further and further into Venus's atmosphere.

The gravity of Venus is ten times higher than that of Mars. The heat generated as a cube ofvelocity is two times higher than at Mars. The lower aerobraking regime has to be targeted by EnVision.

Artist impression of ESA’s EnVision mission at Venus. Credit: ESA/VR2Planets/Damia Bouic

We are going to experience double the solar intensity of Earth's, with the thick white clouds of the atmosphere reflecting a lot of sunlight straight back to space, which needs to be taken into account. We had to reckon with the fact that atomic oxygen was only experienced in low Earth orbit.

During the first decades of the space age, this was not known. The thermal blankets of the Space Shuttle were severely eroded when it returned from low altitude in the early 1980's.

The culprit was a group of individual atoms of oxygen at the fringes of the atmosphere that were broken apart by the sun's rays. All missions below 1000 km need to resist atomic oxygen.

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

The atomic oxygen at the top of the Venusian atmosphere is more than 90 times thicker than the Earth's.

The concentration is quite high, with one pass it doesn't matter, but over thousands of times it starts to accumulate and ends up with a level of atomic oxygen fluence.

At the end of the year, the results of a test of materials will be announced.

To understand how Venus and Earth evolved differently, EnVision will use an array of instruments.

DAVINCI+ is a mission to understand the atmospheric evolution of Venus and VERITAS is a mission to map the Venusian surface. There are two missions that are going to be launched in the next two decades.

There is a press release from the European Space Agency.

The EnVision mission summary.