Low Cost Planetary Missions Conference 2013 Picture: Etna lava flow, with Catania in the background
Venus Express: a low cost mission Mars Express Venus Express Astrium, ESA Astrium, ESA 2001: Call for ideas for re-flight of Mars Express spacecraft bus 2002: Selection & approval Nov 2005: launch Apr 2006: Venus Orbit Insertion
VEx science payload Name Instrument Principal Investigator ASPERA Analyser of Space Plasma and Energetic Ions S. Barabash, IRF,. MAG* Magnetometer T. Zhang, IWF, Graz, Austria. PFS Planetary Fourier Spectrometer (IR) SpicaV/SOIR* UV-IR spectrometer for stellar and solar occultation V. Formisano, IFSI- CNR, Rome, Italy. J.-L. Bertaux, LATMOS, France. VERA Venus Radio Science B. Häusler, Uni-BW, Muenchen, Germany. VIRTIS* VMC* UV-Vis-IR Mapping spectrometer Venus Monitoring Camera P. Drossard, Obs de Paris, Meudon, France, G. Piccioni, IASF- CNR, Rome, Italy. W. Markiewicz, MPS, Germany Payload is (mostly) recycled from Mars Express and Rosetta missions
Venus Express results The original science objectives for Venus Express were organized in seven themes Atmospheric Dynamics Atmospheric Structure Atmospheric Chemistry and Processes Clouds and Hazes Energy balance and greenhouse effect Surface, Geology and Surface-Atmosphere interaction Plasma environment and solar wind interaction Most of the original objectives have been reached and/or superseded. By now we have well over 300 (peer-reviewed) VEx publications The following slides present just a few recent highlights...
Atmospheric Dynamics: Winds at different levels Venus Express provided the first ever 3-D determination of winds at different altitudes on Venus. Hueso et al., 2012 Now VEX reveals dramatic 30% increase in super-rotation rate over 6 years. Kouyama et al., 2013; Khatuntsev et al., 2013.
Atmospheric Dynamics Polar Vortex Polar vortex circulation a generic feature of planetary atmospheres is particularly spectacular and chaotic on Venus (Garate-Lopez et al., 2013) Upper cloud/haze (~70 km) Middle cloud-tops (~60 km) Limaye et al., 2009 IAPS/INAF
Upper Atmosphere Dynamics Evidence of Solar to anti-solar circulation in the upper atmosphere by oxygen glow at and around the anti-solar point from recombination of oxygen atoms. O, NO, CO2, H non-lte emissions mapped. Pag. 7
Upper Atmosphere Dynamics O2 airglow emission at ~ 97 km suggest weak or no super-rotation VIRTIS, SPICAV Pag. 8
Upper Atmosphere Dynamics O2 airglow emission at ~ 97 km suggest weak or no super-rotation VIRTIS, SPICAV Pag. 9 NO airglow emission at ~ 115 km suggests super-rotation! Stiepen et al., in press, 2013 If there is no longer super-rotation at 100 km altitude, how do its effect persist at 115 km?!?
Atmospheric structure & convection A mystery: why are more gravity waves observed at high latitudes? Influence of topography? Latitude [deg] 90 60 30 0-30 -60 >9.0 9.700 9.000 8.000 7.000 6.000 5.000 4.000 3.000 2.000 1.000 0.0-1.000-2.000-2.0 Topographic elevation [km] E p < 1.0 1.0 < E p < 2.0 2.0 < E p < 3.0 E p > 3.0 Magellan topographical map [Ford & Pettengill, 1992] -90 0 60 120 180 240 300 360 East Longitude [deg] [Tellmann et al., 2012]
Atmospheric structure Radio occultation profiles 10 1 DOY 122 2007 lat: - 7.5 DOY 132 2007 lat: - 46.1 DOY 142 2007 lat: - 77.3 DOY 148 2007 lat: - 87.0 86 Pressure [Pa] 10 2 10 3 10 4 10 5 Clouds 76 65 50 Altitude, km 150 200 250 300 350 400 450 Temperature [K] Tellmann et al. 2009
Atmospheric structure Radio occultation profiles low latitudes middle latitudes high latitudes Tropopause Tellmann et al. 2009
Atmospheric structure & convection Imamura et al., 2013
Atmospheric structure & convection Convection is suppressed, not enhanced, at subsolar point! Cloud-level convection is enhanced at high latitudes and at night. Imamura et al., 2013
Atmospheric structure & convection At high latitudes, gravity waves from deep atmosphere can filter through to mesosphere where they are detected by radio scence. Latitude [deg] 90 60 30 0-30 -60-90 0 60 120 180 240 300 360 East Longitude [deg] >9.0 9.700 9.000 8.000 7.000 6.000 5.000 4.000 3.000 2.000 1.000 0.0-1.000-2.000-2.0 Topographic elevation [km] E p < 1.0 1.0 < E p < 2.0 2.0 < E p < 3.0 E p > 3.0 Magellan topographical map [Ford & Pettengill, 1992] [Tellmann et al., 2012]
Atmospheric chemistry Solar and stellar occultation
Atmospheric chemistry Summary of VEx preliminary measurements O 3
Tsang et al., 2008
Cottini et al., 2012
Belyaev et al., 2012
Atmospheric chemistry - Mesospheric SO 2 changes Venus Express finds episodic injection of SO 2 into mesosphere. Marcq et al, 2012 Is this an connected with volcanic activity (like Pinatubo)? Or is it dynamical variability (like El Niño / La Niña)?
Clouds & Hazes
Clouds & Hazes Ignatiev et al., 2009 Cloud-top height measured on the dayside by measuring depth of CO 2 absorption line in reflected sunlight (Ignatiev et al., 2007) No variation at low latitudes; decrease of ~7 km toward poles
Clouds & Hazes Zhang et al, 2010 H2SO4 hazes extend to > 90 km, are very variable. Complex mixed phase chemistry similar to Earth polar stratospheric cloud chemistry. Wilquet et al, 2012
Surface mapping - Thermal emission at 1 µm Idunn Mons VEx has found high emissivity areas interpreted as fresh (unweathered) lava flows around volcanoes. The search for temperature anomalies continues. VIRTIS, Mueller, Smrekar et al.
Induced magnetosphere response to changing solar wind Wei et al., 2012
Induced magnetosphere response to changing solar wind Wei et al., 2012 ASPERA, MAG
Upper atmosphere density variations VEx atmospheric drag experiment ESA Large day-to-day density variations found.
VEx aerobraking phase - 2015 VEx propellant will run out in 2015 (TBC). Before end of mission, an aerobraking phase is proposed. Draft orbit control plan Pericentre altitude (km) Permits density measurement down to 130 km (below homopause). Only limited science pointings will be supported in this phase.
Conclusions 10 productive (Venus) years at Venus First global monitoring of the composition of the lower atmosphere in the near IR transparency windows First application of the solar/stellar occultation technique at Venus First coherent observations of Venus in the spectral range from UV to thermal infrared First coherent study of the atmospheric temperature and dynamics at different levels First study of the middle and upper atmosphere dynamics from O2, O, and NO emissions First use of 3D ion mass analyzer, high energy resolution electron spectrometer, and energetic neutral atom imager First measurements of the non-thermal atmospheric escape First measurements of global surface temperature distribution from orbit First operational experience of aerobraking for ESA 2015?
VEx aerobraking phase - 2015 Draft orbit control plan Pericentre altitude (km) Science during aerobraking: atmospheric densities will be obtained down to 130 kilometres altitude (c.f. 165 km in nominal science operations).