Thomas Widemann. Richard Ghail. Colin Wilson. Lead Proposer. Science Investigation Lead. Programme Management Lead

Transcription

1 Richard Ghail Lead Proposer Thomas Widemann Programme Management Lead Colin Wilson Science Investigation Lead 30 th November 2016 VEXAG 14 Rich Ghail EnVision: European Plans for Venus

2 Key Science Goals: Determine the level and nature of current geological 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. Using r.m.s. slope as a proxy for crustalscale strain reveals strain partitioning into strong lowland terranes bounded by weak deformation belts and weaker uplands 30 th November 2016 VEXAG 14 Slide 2 Rich Ghail EnVision: European Plans for Venus

3 Key Science Goals: Determine the level and nature of current geological 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. Using r.m.s. slope as a proxy for crustalscale strain reveals strain partitioning into strong lowland terranes bounded by weak deformation belts and weaker uplands 30 th November 2016 VEXAG 14 Slide 3 Rich Ghail EnVision: European Plans for Venus

4 Key Science Goals: Determine the level and nature of current geological 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. Using r.m.s. slope as a proxy for crustalscale strain reveals strain partitioning into strong lowland terranes bounded by weak deformation belts and weaker uplands 30 th November 2016 VEXAG 14 Slide 4 Rich Ghail EnVision: European Plans for Venus

5 Key Science Goals: Determine the level and nature of current geological activity Determine the sequence of geological events that generated its range of surface features We are more used to thinking about rifts and other structural features than the terranes bounded by them. Note the distributed low level interior strain 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. 30 th November 2016 VEXAG 14 Slide 5 Rich Ghail EnVision: European Plans for Venus

6 Key Science Goals: Determine the level and nature of current geological 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 Global Zonal Reconnaissance Exploration Locality Coverage >95% >95% >20% >2% >0 2% Unit Area Global km km km 5 5km Resolution 50km 150m 30m 6m 1m Feature Size 150 km 500 m 100 m 20 m <4 m Geomorphological Features Structures Terra continents, Planitia Chasmata, Dorsa Folds, graben Fault scarps Volcanoes Volcanic rises (Regio) Volcanic edifices Lava Flows Flow textures Sediments Featureless plains Parabolas, halos Landslides Dunes Understand the organising geodynamic framework that controls the release of internal heat over the history of the planet. 30 th November 2016 VEXAG 14 Slide 6 Rich Ghail EnVision: European Plans for Venus

7 Key Science Goals: Determine the level and nature of current geological 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 Goal Measurement Resolution Instrument Surface change < ±1cma ¹ at m spatial VenSAR I Geomorphology Images at m spatial VenSAR P Topography at m vertical, m spatial VenSAR P Specified targets Images at 1 10 m spatial VenSAR H / VenSAR S Subsurface structure Profiles at m vertical and m spatial SRS Thermal emissivity Signal to noise >100 at <50 km spatial VEM M, VenSAR R SO₂ concentration < ±1% at <300 km spatial and km altitude VEM H / VEM U H₂O concentration < ±10% at <300 km spatial and <15 altitude VEM H / VEM U D/H ratio < ±10% at <300 km spatial and <15 altitude VEM H Gravity field Spherical harmonic degree and order 120 Tracking Spin Rate < ±10 ⁸ (1 minute in one Venus day) VenSAR S + Tracking Spin Axis < ±0 001 in right ascension and declination VenSAR I Understand the organising geodynamic framework that controls the release of internal heat over the history of the planet. 30 th November 2016 VEXAG 14 Slide 7 Rich Ghail EnVision: European Plans for Venus

8 Shrouded in permanent clouds, the 90 bar, 750 K Venus atmosphere is prohibitive for surface rovers and opaque at wavelengths shorter than ~3 5 cm. In other respects the atmosphere is benign: The total electron count is <1 TeV IR brightness temperature ~50 K cooler than Earth Drag free orbits above 220 km altitude EnVision s InSAR coherence requirement drives our choice for an S band radar. 30 th November 2016 VEXAG 14 Slide 8 Rich Ghail EnVision: European Plans for Venus

9 NovaSAR will consist of four small low cost SAR satellites providing global continuous environmental management and disaster monitoring. The first is being funded by the UK government for launch in early VenSAR is undergoing design work to harden against thermal and ionising radiation during interplanetary cruise and at Venus. During operations, the extreme thermal range during the short orbit effectively limits the operating time to about 15 minutes per orbit. 30 th November 2016 VEXAG 14 Slide 9 Rich Ghail EnVision: European Plans for Venus

10 Level 1 data Single look complex images (SLC) Multi look map oriented images (GRD) Radiometry profiles Initial ephemeris data Level 2 data Interim geocoded image mosaics Orbit orbit interferograms Revised ephemeris data Level 3 data Ground surface change / deformation maps Geocoded & orthorectified image mosaics Digital Elevation Models (gridded at 60 m) Resolution Looks Tx Incidence Sensitivity Swath Duration Data VI1 InSAR 27 m 18 4% dB 53km 498s 66Mbps VI2 InSAR 27 m 18 4% dB 53km 498s 68Mbps VI3 InSAR 27 m 18 4% dB 53km 498s 66Mbps VP1 StereoPolSAR 30 m 9 4% db 53 km 873 s 127 Mbps VH1 HiRes 6 m 6 20% db 22 km 291 s 353 Mbps VH2 HiRes 6 m 6 20% db 32 km 291 s 513 Mbps VS1 Spotlight 1 m 1 20% db 5 km 4 s 468 Mbps 30 th VR1 Radiometry 5 30 km n/a 0% 4 +4 ~1 K 38 km <2760 s <0 25 kbps November 2016 VEXAG 14 Slide 10 Rich Ghail EnVision: European Plans for Venus

11 Simulated Magellan 110 m resolution SAR image of Holuhraun, Iceland (derived from Sentinel 1a data). Notice the low contrast from 2 bit BAQ compression and foreshortening due to lack of appropriate DEM. Simulated 30 m resolution HHVHVV StereoPolSAR image (derived from Sentinel 1a data). Note the new lava flow in blue at lower left. Scale bar in all images is 2 km. 30 th November 2016 VEXAG 14 Slide 11 Rich Ghail EnVision: European Plans for Venus

12 Simulated Magellan 110 m resolution SAR image of Holuhraun, Iceland (derived from Sentinel 1a data). Notice the low contrast from 2 bit BAQ compression and foreshortening due to lack of appropriate DEM. Simulated 6 m resolution HiRes image (derived from TerraSAR X data). Simulated 30 m resolution HHVHVV StereoPolSAR image (derived from Sentinel 1a data). Note the new lava flow in blue at lower left. Scale bar in all images is 2 km. 30th November 2016 VEXAG 14 Slide 12 Rich Ghail EnVision: European Plans for Venus

13 NovaSAR 6 m airborne test data, Pembroke Dock Simulated Magellan 110 m resolution SAR image of Holuhraun, Iceland (derived from Sentinel 1a data). Notice the low contrast from 2 bit BAQ compression and foreshortening due to lack of appropriate DEM. Simulated 6 m resolution HiRes image (derived from TerraSAR X data). Simulated 30 m resolution HHVHVV StereoPolSAR image (derived from Sentinel 1a data). Note the new lava flow in blue at lower left. Scale bar in all images is 2 km. 30th November 2016 VEXAG 14 Slide 13 Rich Ghail EnVision: European Plans for Venus

14 The Radar Sounder for EnVision can acquire information on the shallow subsurface with the following main scientific goals: Characterisation of the different stratigraphic and structural patterns of the subsurface. Study the volcanism phenomena and their impact on the geological evolution of the Venusian topography. Detection of subsurface structures non directly linked with surface. Analysis of the materials in the surface and subsurface and their metamorphism linked to the burial process. Synergistic analysis of the data provided by SAR and radar sounder sensors to study the evolution of the planet. Analysis of the total electron content of the ionosphere. One of the main issues for the design of the radar sounder instrument for EnVision concerns the physical and electromagnetic modelling of the surface and subsurface targets. Transmitted central frequency (fc) Transmitted bandwidth (Bw) Antenna type Antenna dimension Power Along track resolution Across track resolution Vertical resolution Estimated maximum penetration depth Data rate Mass (without antenna) Size Pointing requirements In the range 6 30 MHz In the range 2 10 MHz Dipole (deployable) TBD (depending on the central frequency) 30 W < 1 km < 5 km 75 m (Bw=2 MHz) 15 m (Bw=10 MHz) (vacuum) 1.5 Km (fc=6 MHz) 600 m (fc=30 MHz) kbps (depending on selected parameters and operation scenarios) 10 kg cm Nadir SHARAD radargram over a portion of western Medusae Fossae Formation, a lowdensity pyroclastic deposit spanning across the crustal dichotomy of Mars. The deposit labelled "North Hill (nh) is about 500 m thick (taken from [6]). 30 th November 2016 VEXAG 14 Slide 14 Rich Ghail EnVision: European Plans for Venus

15 The Radar Sounder for EnVision can acquire information on the shallow subsurface with the following main scientific goals: Characterization of the different stratigraphic and structural patterns of the subsurface. Study the volcanism phenomena and their impact on the geological evolution of the Venusian topography. Detection of subsurface structures non directly linked with surface. Analysis of the materials in the surface and subsurface and their metamorphism linked to the burial process. Synergistic analysis of the data provided by SAR and radar sounder sensors to study the evolution of the planet. Analysis of the total electron content of the ionosphere. One of the main issues for the design of the radar sounder instrument for EnVision concerns the physical and electromagnetic modelling of the surface and subsurface targets. SHARAD radargram over a portion of western Medusae Fossae Formation, a lowdensity pyroclastic deposit spanning across the crustal dichotomy of Mars. The deposit labelled "North Hill (nh) is about 500 m thick (taken from [6]). 30 th November 2016 VEXAG 14 Slide 15 Rich Ghail EnVision: European Plans for Venus

16 VIRTIS has mapped the hot surface at 1 μm using emissivity data [Helbert, Müller, et al & Müller, Helbert et al. 2009, 2010] VEM M spectral bands and science themes Key Parameter Value Instrument Concept Pushbroom design FOV / swath 60 / 250 km Detector SOFRADIR Neptune 500 X 256 HgCdTe array Cooled focal plane 150 K, pulse tube cooler 14 spectral bands Bandwidth < 10 nm Variation < 1nm Processed Data Rate 190 kb/s (1 Mb/orbit) Mass / Power (CBE) ~5.4 kg / ~18.5 W Volume 30 cm x 30 cm x 40 cm 30 th November 2016 VEXAG 14 Slide 16 Rich Ghail EnVision: European Plans for Venus

17 VEM H is a spectrometer probing the near infrared nightside windows with very high spectral resolution (resolving power ~ 40,000). It will: Quantify SO₂, H₂O and HDO in the lower atmosphere Characterise of volcanic plumes Detect other sources of gas exchange with the surface Complement VenSAR and VEM M surface observations E. Marcq et al. (Venus Express); L. Esposito et al. (earlier data); image ESA/AOES Medialab Left: the optical assembly, which is inverted and mounted on a baseplate on the underside of the radiator. Right: the SOFRADIR detector for NOMAD on ExoMars. VEM U is a small, light, UV spectrometer which will map mesospheric SO₂ abundances on the dayside of Venus. Together with VEM M and VEM H it will link surface, tropospheric and mesospheric changes in SO₂, H₂O and other gases. 30 th November 2016 VEXAG 14 Slide 17 Rich Ghail EnVision: European Plans for Venus

18 Preliminary simulations indicate that an accuracy of ~ in k₂ is achievable by stacking together 3 years of navigation tracking data of EnVision spacecraft, more than sufficient to distinguish between different models of internal structure. Venus apparently rotated more quickly during the period of the Magellan mission (small red error bars, ) than it did in the first Earth based observations (green) or in later measurements from Earth and by Venus Express (blue). Vertical bars indicate measurement uncertainty, horizontal bars the period over which the measurement was made. 30 th November 2016 VEXAG 14 Slide 18 Rich Ghail EnVision: European Plans for Venus

19 EnVision is a 2m cubic platform with a dry mass of 950 kg. Planned for launch from an Ariane 6.2 in October 2029, 200 days aerobraking are anticipated to achieve the 259 km altitude circular polar orbit. The following operating modes are planned during each 24 hour period: Communications mode: 5½hourHGAEarth pointed, solar array oriented towards the Sun, one axis degree of freedom; VenSAR mode: <15 minutes, inertial 3 axes pointed, nadir face facing Venus centre, rolled by up to ±35 around the spacecraft velocity vector (x axis); and Night side science mode: 45 minute nadir face facing Venus centre, inertial 3 axes pointed. Telemetryisprovidedbyafixed3 m, 65 W RF, Ka band high gain antenna. With GMSK (0 5) modulation and 1/4 Turbo codes, a minimum link rate of 4 Mbps is achieved. Platform could support a secondary Cubesat payload 30 th November 2016 VEXAG 14 Slide 19 Rich Ghail EnVision: European Plans for Venus

20 30 th November 2016 VEXAG 14 Slide 20 Rich Ghail EnVision: European Plans for Venus

21 30 th November 2016 VEXAG 14 Slide 21 Rich Ghail EnVision: European Plans for Venus

22 We have a very poor understanding of Venus, particularly its surface materials High resolution imagery, topography and compositional data are needed to understand D InSAR change detection will determine the location and nature of geological activity on Venus today Surface, tropospheric and mesospheric volatile measurements will characterise geochemical cycles Calibrated polarimetric and high resolution contextual imagery of the Venera landing sites is needed to understand what the landers imaged EnVision will take our knowledge of Venus towards that of Mars today Venera 13 landing site [Don P. Mitchell] 30 th November 2016 VEXAG 14 Slide 22 Rich Ghail EnVision: European Plans for Venus