EnVision (spacecraft)

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EnVision is a proposed orbital mission to Venus, considered for ESA's fifth medium class mission (M5) in its Cosmic Vision programme. Design by the ESA/ESTEC EnVision study team. Artwork by VR2Planets.

EnVision
Mission typeReconnaissance
OperatorESA
Websiteenvisionvenus.eu
Mission duration4.5 years (nominal)
Spacecraft properties
ManufacturerThales Alenia Space[1]
Launch mass2607 kg
BOL mass2537 kg (notional)[1]
Dry mass1277 kg
Payload mass255 kg
PowerMax. 2.35 kW
Start of mission
Launch date2032 (proposed)
RocketAriane 6.2[2][1]
Launch siteGuiana Space Centre (CSG)
ContractorArianespace
Venus orbiter
Orbital parameters
Peri altitude220 km
Apo altitude470 km
Transponders
BandX band, Ka band[1]
← ARIEL
 

EnVision is a proposed orbital mission to Venus that would perform high-resolution radar mapping and atmospheric studies.[3][1] 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.

Overview[edit]

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 other two finalists are SPICA, an infrared space telescope, and THESEUS, a gamma-ray space observatory. The winner will be selected in 2021 and it would launch in 2032.[4][5]

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.[4] EnVision would be capable of detecting centimeter-scale surface changes that would enable characterisation of volcanic and tectonic activity, and estimate rates of weathering and surface alteration.[1] The Subsurface Radar Sounder would image faults, stratigraphy and weathering in the upper ~100 m of the areas mapped, to identify structural relationships and geological history.[2] The mission cost is estimated at €544 million euros.[1]

The Lead Scientist of EnVision is Richard Ghail, Royal Holloway, University of London.[6] The deputy lead proposers are Colin Wilson, University of Oxford, UK (Science investigation lead) and Thomas Widemann, Paris Observatory, France (Programme management lead).[2][7]

Science goals[edit]

The core goal of EnVision is to detect activity and measure small-scale changes on Venus, including geological and geochemical cycles involving the interior, surface and atmosphere. EnVision will use a number of different techniques to search for active geological processes, measure changes in surface temperature associated with active volcanism, characterise regional and local geological features, determine crustal support mechanisms and constrain mantle and core properties. The mission would repeatedly observe specific targets (~20% of the surface) with the widest possible range of measurements to fully characterise these areas.[2] Core science measurements are: high-resolution mapping of specific targets, surface change, geomorphology, topography, subsurface, thermal emission, SO
2
, H
2
O
, D/H ratio, gravity, spin rate, and spin axis. The specific mission's goals are:[1]

  • Determine the level and nature of current activity.
  • Determine the sequence of geological events that generated its range of surface features.
  • Assess whether Venus once had oceans or was hospitable for life.
  • Understand the organising geodynamic framework that controls the release of internal heat over the history of the planet.

Science payload[edit]

The notional payload consists of three instruments:[1][2][4]

  • Venus Synthetic Aperture Radar (VenSAR) operates at 3.2 GHz in the S band (9.4 cm wavelength) for spatial resolutions of 1 – 30 m.[8] Operating at a frequency below 30 MHz has the advantage that the signal penetrates the ground, providing information on subsurface structures that are crucial to understanding the history of Venus. A sounder in the 9-30 MHz range is able to penetrate to a crustal depth of 750–340 m respectively and image subsurface features at a vertical resolution of 5–16 m. An earlier version of the proposal intended to use spare parts produced for the Earth-orbiting Sentinel-1 satellite.[9] The Principal Investigator of VenSAR is Richard Ghail, Royal Holloway, University of London, UK.[2]
  • Venus Spectroscopy suite (VenSpec) consists of three channels: VenSpec-M, VenSpec-H and VenSpec-U.
    VenSpec-M would provide compositional data on rock types; VenSpec-H would perform extremely high resolution atmospheric measurements; and VenSpec-U would monitor sulphured minor species (mainly SO and SO2) as well as the mysterious UV absorber in Venusian upper clouds. This suite would search for temporal variations in surface temperatures and tropospheric concentrations of volcanic gases, indicative of volcanic eruptions. The Principal Investigator of the Venus Spectroscopy suite and PI of VenSpec-M is Jörn Helbert, DLR Institute of Planetary Research, Berlin, Germany. The PI of VenSpec-H is Ann Carine Vandaele, Royal Belgian Institute for Space Aeronomy (BIRA/IASB), Belgium. The PI of VenSpec-U is Emmanuel Marcq, LATMOS, IPSL, France.[2]
  • Subsurface Radar Sounder (SRS) would image faults, stratigraphy and weathering in the upper ~100 m of the areas mapped by VenSAR, to identify structural relationships and geological history. The Principal Investigator of the Subsurface Radar Sounder is Lorenzo Bruzzone, Università di Trento, Italy.[2]

Gravity Science[edit]

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 low-eccentricity, near-polar and relatively low altitude orbit[2] offers the opportunity to obtain a high-resolved 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’ 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 Principal Investigator of EnVision Radio Science and Gravity experiment is Caroline Dumoulin, LPG, Université de Nantes, France. Deputy Principal Investigator is Pascal Rosenblatt, LPG, Université de Nantes, France.[2]

See also[edit]

References[edit]

  1. ^ a b c d e f g h i EnVision: Understanding why our most Earth-like neighbor is so different. M5 proposal. Richard Ghail. arXiv.org
  2. ^ a b c d e f g h i j EnVision M5 Venus Orbiter Proposal: Opportunities and Challenges. (PDF). R. C. Ghail1, C. F. Wilson and T. Widemann. 47th Lunar and Planetary Science Conference (2016)
  3. ^ "ESA selects three new mission concepts for study". Retrieved 10 May 2018.
  4. ^ a b c New ESA Orbiter Might Explain Why Venus Went So Wrong. Bruce Dorminey, Forbes. 8 May 2018.
  5. ^ ESA names space mission concepts in running for Cosmic Vision mission slot. David Szondy, New Atlas. 7 May 2018.
  6. ^ Planet Venus: Hopes rise of new mission to the hothouse world. Paul Rincon, BBC New. 22 March 2019.
  7. ^ "EnVision - Europe's Revolutionary Mission to Venus". EnVision. Retrieved 2019-05-12.
  8. ^ EnVision: understanding why our most Earth-like neighbour is so different. Richard Ghail, Colin Wilson, Thomas Widemann, Lorenzo Bruzzone, Caroline Dumoulin, Jörn Helbert, Robbie Herrick, Emmanuel Marcq, Philippa Mason, Pascal Rosenblatt, Ann Carine Vandaele, Louis-Jerome Burtz. arXive.org; 27 Mar 2017.
  9. ^ Ghail, R; EnVision Team (2012). "EnVision – where next for Venus?" (PDF). European Planetary Science Congress. Retrieved 2018-05-13.