|Mission duration||4.5 years (nominal)|
|Launch mass||2607 kg|
|BOL mass||2537 kg (notional)|
|Dry mass||1277 kg|
|Payload mass||255 kg|
|Power||Max. 2.35 kW|
|Start of mission|
|Launch date||2032 (proposed)|
|Launch site||Guiana Space Centre (CSG)|
|Peri altitude||220 km|
|Apo altitude||470 km|
|Band||X band, Ka band|
EnVision is a proposed orbital mission to Venus that would perform high-resolution radar mapping and atmospheric studies. The mission would help scientists understand the relationships between its geological activity and the atmosphere, and it would investigate why Venus and Earth took such different evolutionary paths. The mission is studied in collaboration with NASA, with the potential sharing of responsibilities currently under assessment.
The concept was selected in May 2018 as a finalist to become the fifth Medium-class mission (M5) of the Cosmic Vision programme by the European Space Agency (ESA). The mission is studied in collaboration with the United States' National Aeronautics and Space Administration (NASA), with the potential sharing of responsibilities currently under science, technical and programmatic assessment. The other finalist is THESEUS, a gamma-ray space observatory. The winner will be selected in 2021 and it would launch in 2032.
If selected, EnVision would be launched on an Ariane 6.2 launch vehicle, giving a cruising time of about five months; after six months of aerobraking around Venus, it would begin a four-year mission at 259 km (161 mi) above Venus' surface. EnVision would be capable of detecting centimetre-scale surface changes that would enable characterisation of volcanic and tectonic activity, and estimate rates of weathering and surface alteration. The mission cost is estimated at €544 million.
The Lead Scientist of EnVision is Richard Ghail, Royal Holloway, University of London. The two deputy lead scientists are Colin Wilson, University of Oxford, UK (Science investigation lead) and Thomas Widemann, LESIA, Paris Observatory, France (Programme management lead).
Core science measurements are: high-resolution mapping of specific targets, surface change, geomorphology, topography, subsurface, thermal emission, SO
2O, D/H ratio, gravity, spin rate, and spin axis. The specific mission's goals are:
Any orbiting spacecraft is sensitive to the local gravity field, plus the gravity field of the Sun and, to a minor extent, other planets. These gravitational perturbations generate spacecraft orbital velocity perturbations, from which the gravity field of a planet can be determined. EnVision's low-eccentricity, near-polar and relatively low altitude orbit offers the opportunity to obtain a high-resolution gravity field at each longitude and latitude of the Venusian globe. The analysis of the gravity field together with the topography gives insights on the lithospheric and crustal structure, allowing to better understand Venus's geological evolution. In the absence of seismic data, the measurements of the tidal deformation and proper motion of the planet provide the way to probe its deep internal structure (size and state of the core). The tidal deformation can be measured in the EnVision orbital velocity perturbations through the gravitational potential variations it generates (k2 tidal Love number).
The co-Principal Investigators of EnVision Radio Science and Gravity experiment are Caroline Dumoulin, LPG, Université de Nantes, France, and Pascal Rosenblatt, LPG, Université de Nantes, France.