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What world-wide firsts will EnVision accomplish during its mission?

What is the expected science return from EnVision?


While still fitting in the medium class mission price envelope, EnVision aims to deliver never before accomplished science and capability. EnVision is the first mission specifically designed to measure the nature and rate of change of geological processes on Venus. To enable this it embarks as prime payload a highly capable Interferometric Radar (VenSAR), the first ever delivered to another planet. The instrumental suite of EnVision boasts benefits from the latest technology developments and will provide orders of magnitude improvement over previous measurements. The NASA Magellan and ESA Venus Express missions revealed a complex and dynamic planet, demonstrating that the next stage of Venus exploration must focus on its surface as a way to understand its puzzling interior and atmosphere.

Viking and MRO image resolution comparison
Figure 1 : Viking MDIM 230 m/pixel comparable to Magellan. (left) MRO CTX, 7 m/px comparable to proposed VenSAR (right)


Magellan data was capped at 100m best resolution with most of the planet actually covered at around 500m. Compared to the geological process of Venus, this in analogous to the capabilities of the Viking missions to Mars of the 1970s. 
The VenSAR instrument will provide global stereoscopic coverage at 20m resolution as well as be able to operate in a High Resolution mode to image specific target areas at 5m/pixel or better. EnVision will do for this planet what Mars Reconnaissance Orbiter (2005) did for Mars: the potential is a paradigm shift in our understanding of Venus with side effects splashing on comparative planetology on our solar system and beyond.
Lunar exploration has also revealed the importance of good topography to complement high spatial resolution in the interpretation of images and geomorphological processes they uncover. Vertical to horizontal ratio of 1/10 is required for adequate differentiation of overlapping processes significant to uncovering surface history.

simulation of Magellan and EnVision topography capabilities

Figure 2 : Equivalent Magellan topography applied to Tycho crater on the Moon (left) Simulated VenSAR topography (right) [Herrick]

To adequately quantify the rate of change of the surface expression of geological processes, EnVision will make the first interferometric measurements on a planetary body other than Earth. Effectively transposing Earth Observation technology to Venus special constraints, it will provide centimetre scale sensitivity of surface movements. This will allow for first ever direct evidence of ongoing geological activity at Venus. Long term tracking of these changes will yield precious insight into interior dynamics and allow scientists to discriminate between competing models.

Figure 3 : InSAR change tracking of Etna volcano, an Earth based example of VenSAR capabilities. ©ESA/NASA/JPL-Caltech

Related questions:
Official Science Case of the proposal
What is the legacy of Venus Express?
What world-wide firsts will EnVision accomplish during its mission?
What is a Radar exactly? How will the radar work?