EnVision M5 Venus Orbiter Proposal: Opportunities and Challenges

Richard Ghail, Colin F. Wilson, Thomas Widemann

Research output: Contribution to journalArticle


The core goal of EnVision is to detect activity and measure rates of change on Venus, including geological and geochemical cycles involving the interior, surface and atmosphere.It will observe >20% of the surface with all instruments and will obtain gravity and emissivity data globally. The instrument suite for M5 is under review but will likely comprise the same three instruments as at M4: VenSAR, VEM and SRS.VenSAR. The largest payload instrument is a phased array S-band radar, developed from the UK's low-cost NovaSAR-S instrument optimized for Venus. Use of spacecraft pointing for side-looking, instead of a fixed slant, simplifies the observation strategy to three pairs of ~9 minute/orbit (~36° latitude, ~3800 km) pass-to-pass InSAR swaths, two ~9 minute/orbit multipolar (HH-HV-VV) swaths at lower incidence angle for stereo mapping, two ~3 minute/orbit (~12° latitude, ~1300 km) high resolution swath and 1 to 2 S-band emissivity swaths per day plus 50 km2 ~1 m resolution sliding spotlight images. In addition, InSAR will be acquired along a narrow equatorial strip and across the North Pole to measure variability in the spin rate and axis.VEM. The Venus Emissivity Mapper suite comprises two UV and IR spectrometer channels in addition to the VEM-M IR mapping. A filter array provides wavelength stability and maximizes signal to the focal plane array (FPA). VEM-H is high-resolution, nadir-pointing, infrared spectrometer, the ideal instrument to enable characterization of volcanic plumes released from the surface of Venus by observing SO2, H2O and HDO through the 1 µm, 1.7 µm, and 2-2.3 µm atmospheric windows. Specifically, VEM-H is a redesign of the LNO (Limb, Nadir and Occultation) channel of NOMAD, retaining much heritage from the original with minor modifications to meet the science objectives of the M5 EnVision mission. The third channel, VEM-UV is an upper-atmosphere UV spectrometer dedicated to global SO2 & sulfur cycles.SRS. The Subsurface Radar Sounder will image faults, stratigraphy and weathering in the upper ~100 m of the areas mapped by VenSAR, to identify structural relationships and geological history.
Original languageEnglish
JournalAmerican Astronomical Society, DPS meeting #48
Publication statusPublished - 1 Oct 2016

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