EnVision Mission

EnVision is ESA's next mission to Venus, and consists of an orbiter hosting five payloads and one experiment exploiting the spacecraft radio link.

Spacecraft

The spacecraft will be a roughly rectangular three-axis stabilised satellite, weighing approximately 4.1 tonnes at launch (1.7 tonnes dry mass), measuring approx. 2 m x 2 m x 3 m in stowed configuration, with two deployable solar arrays. It will have a power budget of around 3 kW and a large volume (200 Tbits) of science data to be downlinked to Earth with a fixed 2.5 m High Gain Antenna. Notable characteristics are the high-thruster main engine, the X-Ka band TT&C system, and the reltively long aerobraking phase (11 months).

High-thrust main engine

The mission profile requires a high thrust (1kN) main engine for orbital manoeuvres. The identified engine, LEROS 4 from Nammo (UK), is under development. It uses bi-propellant (MON-3/MMH) and its specific impulse is ~320s. It has achieved TRL5 as of November 2023 as part of an ESA-led Technology Development Activity. Testing of the Engineering Model (EM) has been completed successfully, and the Critical Design Review is planned in Q4 2024. A Qualification Model will then be built, and the qualification testing is planned in Q2 2025.

Artist impression of EnVision spacecraft deployment. Copyright: European Space Agency / Paris Observatory / VR2Planets / Damia Bouic.

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Launch, planetary transfer, and Venus orbit phases

The EnVision launch is scheduled for November 2031, with back-up dates in 2032 and 2033. The mission will launch with an Ariane 64 rocket (direct escape).

The interplanetary cruise phase will take around 15 months.

The Venus orbit insertion will be highly elliptic, and the final science orbit will be reached by means of Aerobraking. The Aerobraking phase will take around 11 months, and will be followed by a 2-months in-orbit commissioning phase prior to the science operation phase.

The EnVision science operation phase duration is 6 Venus cycles (about 4 Earth years), and is schedule to start mid-2034.

Scetch of EnVision launch, inter-planetary transfer, Venus orbit launch insertion, aerobraking, and science orbit.

Science Data downlink

The science data downlink capability is ~200 Tbits using Ka-/X-band comms system with a >2.5 m diameter fixed high-gain antenna.

Science orbit and data coverage

The spacecraft orbit will be polar, with a duration of ~92 minutes and an inclination between 87o and 89o. The orbit will be elliptical, with spacecraft altitudes varying between ~220 and 510 km above the surface.

The slow rotation rate of Venus leads to a slow build-up of the observation coverage of the planet during the 6 Venus sideral days (~4 Earth years) mission duration. The orbit will drift during the science operations phase, but will be phase controlled.

Simulation of the measurement track of one of the EnVision payloads during half an orbit.

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