fig 1. EnVision concept
|EnVision is a proposed ESA medium-class mission to determine the nature and current state of geological activity on Venus, and its relationship with the atmosphere, to understand how Venus and Earth could have evolved so differently.
It will use a subsurface radar sounder to obtain profiles of the upper few hundred metres, and an IR mapper and spectrometer to detect volcanic eruptions and a world-leading European phased array synthetic aperture radar, VenSAR, to obtain global topography at 27m and imagery at up to 1m resolution, and us InSAR to detect changes of < 1cm/yr
The use of a low frequency nadir looking radar sounder provides the ideal complementary information to the SAR data acquired by the S-band VenSAR, enabling a full and detailed investigation of the surface and subsurface geology of Venus. The combination of InSAR data (intensity, topography and displacement variables) with the sounder data results in an exceptional ability to understand the link between the surface and subsurface processes on Venus.
fig 2. Nominal Spacecraft Layout. Credits EnVision Team.
To achieve the science requirements, the radar shall be designed to work with a central frequency in the range 9 to 30 MHz for optimal ground penetration capability. The radar bandwidth shall be of several MHz to achieve adequate range resolution. The SRS maximum penetration depth, which has been inferred from the various dielectric measurements in different types of basaltic rocks.
fig 3. Scheme illustrating data processing flow and related data products. Credits EnVision Team.
The pipeline for Level 1b (L1b) processing will use as input both scientific and engineering telemetry of the instrument, and the orbital information of the spacecraft. Data will be split into individual files, one for each type of telemetry and for every observation, with packets arranged in time order, and corrupted or duplicated packets removed. For scientific telemetry packets, a set of parameters describing the geometry of observation will be computed using orbital information of the spacecraft
SRS heritage includes RIME (Radar for Icy Moon Exploration) onboard JUICE (Jupiter Icy Moon Explorer), MARSIS (Mars Express) and SHARAD on NASA’s Mars Reconnaissance Orbiter.
- Ghail, Richard, et al. “EnVision: understanding why our most Earth-like neighbour is so different.” arXiv preprint arXiv:1703.09010 (2017).