This van-sized spacecraft will surf Venus' atmosphere to understand why it's so different from Earth

Venus and Earth are quite similar in terms of size, composition and distance from the Sun, yet they have evolved very differently. To understand why our closest neighbour is so different, a new ESA-led mission, EnVision, will perform optical, spectral and radar mapping of the planet.

EnVision is targeting a launch in the early 2030s from ESA's Spaceport in Kourou, French Guiana on an Ariane 62. It will be the first mission to investigate Venus from its inner core to its upper atmosphere to provide a holistic view of the Earth's sister planet, studying the planet's history, activity and climate.

Before getting down to work, the van-sized spacecraft needs to perform aerobraking - lowering its orbit with thousands of passages through Venus' hot, thick atmosphere for up to two years.

This phenomenon was used operationally for the first time in 2017 by the agency's ExoMars Trace Gas Orbiter (TGO) to lower its orbit around Mars over an 11-month period.

"Aerobraking around Venus is going to be much more challenging than for TGO. To begin with, the gravity of Venus is about 10 times higher than that of Mars. This means velocities about twice as high as for TGO will be experienced by the spacecraft when passing through the atmosphere – and heat is generated as a cube of velocity," explains ESA's EnVision study manager Thomas Voirin.

EnVision is currently undergoing testing at a unique ESA facility to check if its material can safely withstand this challenging process of atmospheric surfing. The Low Earth Orbit Facility (LEOX) is specifically built by ESA to simulate atomic oxygen in orbit.

"We want to check that these parts are resistant to being eroded, and also maintain their optical properties – meaning they do not degrade or darken, which might have knock-on effects in terms of their thermal behaviour, because we have delicate scientific instruments that must maintain a set temperature. We also need to avoid flaking or outgassing, which lead to contamination," Thomas added.

For this mission, NASA will be providing its Synthetic Aperture Radar instrument, VenSAR and Deep Space Network support for critical mission phases.