EnVision - European Space Agency
EnVisionCDF Study – ExecutiveSummaryPrepared by ESA Study and CDF*Teams(*) ESTEC Concurrent Design FacilityESA UNCLASSIFIED – Releasable to the Public
Outline Introduction System design CDF Study Objectives Mass budgets Mission and System DesignSummary Conclusions Points for attention for phase A(spacecraft platform) Driving requirements andconstraints Payload System trade-offs, system options Concept of operationsEnVision Slide 2ESA UNCLASSIFIED – Releasable to the PublicSystem
IntroductionESA UNCLASSIFIED – Releasable to the Public
Introduction The Call for M5 Mission Proposals was issued in April 2016. ESA received 25 valid proposalsthat underwent a selection process that has led the recommendation of three ESA-ledcandidates missions by the Space Science Advisory Committee (SPC(2018)17):– EnVision, to determine the nature and current state of geological activity on Venus,and its relationship with the atmosphere, in collaboration with NASA– SPICA, the Space Infrared observatory for Cosmology and Astrophysics using a 2.5m cryogenic telescope, in collaboration with JAXA– THESEUS, a transient high energy sky and early universe surveyor, to explore theearly universe with Gamma-ray bursts and to monitor the X-ray transient universe. ESA Phase 0 internal studies were carried out for all 3 missions within ESA’s ConcurrentDesign Facility, between June 2018 (SPICA) and November 2018 (ENVISION). Note : Envision original M5 proposal is publicly available s/2011-07-07/envisionm5 proposal without annexes pdf 12334.pdfEnVision Slide 4ESA UNCLASSIFIED – Releasable to the PublicSystem
Context for Envision---Envision is a Venus orbiter mission addressing the following science questions :-is Venus geologically active ? How has Venus geologically evolved with time ?-How Venus atmosphere is linked to its geology ? How does Venus interior work ?Carrying 6 experiments (an S-band Synthetic Aperture Radar performing Interferometry SAR, aSubsurface Radar Sounder, a suite of 3 spectrometers, a Radio Science Experiment), Envisionwill answer these questions by a set of complementary measurements :-cm-scale surface change detection mapping by radar interferometry (InSAR) over themost likely active regions of interest ( 20% of the surface)-Nearly-global Topography, mineralogy, thermal emissivity, sub-surface and gravity fieldmapping-Nearly-global atmosphere characterizationThe mission is studied in collaboration with NASA, with the potential sharing of responsibilitiescurrently under assessmentEnVision Slide 5ESA UNCLASSIFIED – Releasable to the PublicSystem
CDF Study objectivesESA UNCLASSIFIED – Releasable to the Public
CDF Study Objectives1. Design-to-cost a reference mission, spacecraft design and mission profile– Accommodation of the instruments– Orbital / mission trajectory design– Science operations plan2. Assess and consolidate potential NASA contributions to the mission-Details for NASA-provided contributions were not available at the time of theCDF-CDF technical assessment was performed with the initially proposed radarinstrument concept-CDF outcomes were used to derive requirements towards potential NASAprovisions3. Identify technology development activities4. Estimate the cost of the mission, its development time, and risksEnVision Slide 7ESA UNCLASSIFIED – Releasable to the PublicSystem
Mission Summary - Chemical PropulsionScience Case Is Venus geologically active ? How has Venus geologically evolved withtime ? How Venus atmosphere is linked to itsgeology ? How does Venus interior work ?PayloadTotal mass: 254 kg (incl. 30% payloadmargin)Synthetic Aperture Radar (VenSAR)Subsurface Radar (SRS)Spectrometer (VenSpec)Radio Science Experiment (No payload equip.)MeasurementPrinciple cm-scale surface change detectionmapping by radar interferometry over themost likely active regions of interest( 20% of the surface) Nearly-global Topography, mineralogy,thermal emissivity, sub-surface andgravity field mapping by complementarymeasurements Nearly-global atmosphere characterizationSpacecraftMissionProfile Launch with A6.2 into HEO then Escape Baseline launch date 2032 / back-up 2033 0.5 years transfer, 2 years aerobraking(3kW/m2, 0.3 N/m2 – TGO envelope) 2.66 years of science (4 Venus cycles) Science orbit: 220-470 km nearly-polar“frozen ecc. Orbit” 15.7 m2 Solar Arrays incl. 40% OSR Battery 67 kg Fixed 3m HGA, Ka-Band (science), 100WTWTA 2*3.35 m2 radiators on opposite faces Reaction-wheel based slews for sciencetarget acquisitions and Earth pointing Bi-propulsion system, with Large ApogeeEngine for Escape and VOI, and 16 10Nthrusters 2 2 Tbit SSMM included in OBC 242 Tbit data returnMass(with 20%system margin)Dry mass 1277 kgWet mass 2537 kgTotal (wet adapter) 2607 kgPowerPeak: 2.3kWEnVision Slide 8ESA UNCLASSIFIED – Releasable to the PublicSystem
Spacecraft Design – Chemical PropulsionEnVision Slide 9MassDry mass 1277.5 kgWet mass 2537kgTotal (wet adapter) 2607 kgMission Duration4.5 – 6.3 yearsData HandlingOBC with SSMM (2 Tbit 2 Tbit in cold red.), RTUAOCS2x2x2x2xCommunicationsHGA, 2x LGA, Ka-band TWT/EPC, X-band TWT/EPC, RFharness, 2x transpondersChemicalPropulsionBipropulsion System: MON/MMH420 N Main Engine8 8 10 N thruster for AOCSMechanismsSADE, 2x SADM, SRS deployable dipole antennaPowerSolar array (total 15.7 m²), 67 kg battery, PCDU 25 kgStructuresAssembly panels, adapter ring and mountings, bottompanel, HGA bracket, radiator panel, SA attachmentframe, SAR mounting brackets, shear panels, SRSmounting brackets, substrate SA, substrate SAR, toppanel, tank strutsThermal ControlBlack paint, constant conductance heat pipe, hightemperature MLI, heater, Multi Layer Insulation 10 layer,Optical Solar Reflector, thermal filler, doubler,thermistor, thermal strap, thermal washerstar trackersgyros 4x reaction wheelssun sensorsaccelerometersESA UNCLASSIFIED – Releasable to the PublicSystem
Spacecraft Design – Electric PropulsionEnVision Slide 10MassDry mass 1619.5 kgWet mass 2368 kgTotal (wet adapter) 2438 kgMission Duration7-8 yearsData HandlingOBC with SSMM (2 Tbit 2 Tbit in cold red.), RTUAOCS2x2x2x2xCommunicationsHGA, 2x LGA, Ka-band TWT/EPC, X-band TWT/EPC, RFharness, 2x transpondersChemicalPropulsionBipropulsion System: MON/MMH420 N Main Engine8 8 10 N thruster for AOCSMechanismsSADE, 2x SADM, SRS deployable dipole antennaPowerSolar array (total 53.4 m²), 79 kg battery, PCDU 62 kgStructuresAssembly panels, adapter ring and mountings, bottompanel, HGA bracket, radiator panel, SA attachmentframe, SAR mounting brackets, shear panels, SRSmounting brackets, substrate SA, substrate SAR, toppanel, tank strutsThermal ControlBlack paint, constant conductance heat pipe, hightemperature MLI, heater, Multi Layer Insulation 10 layer,Optical Solar Reflector, thermal filler, doubler,thermistor, thermal strap, thermal washerstar trackersgyros 4x reaction wheelssun sensorsaccelerometersESA UNCLASSIFIED – Releasable to the PublicSystem
Driving requirements& constraintsESA UNCLASSIFIED – Releasable to the Public
Driving Requirements and m resolution)20%min. 2- roll-up max. 35deg.- angular baseline 1.4degStereoPol SAR(30m resolution)20%- roll-up max. 35deg.HiRes SAR(6m resolution)2%- roll-up max. 35deg.Spotlight SAR(1m resolution)0.1%- roll-up max. 35deg.SRSGlobal- Night sideVenSpec-M & H60%- Night sideVenSpec-U50%- Day side- Observations on several consecutive orbitsRadio Science 50% with mostinterest in Southhemisphere-EnVision Slide 12Antenna pointed to EarthNo maneuversAt least 6 hours tracking per day250-300km altitudeESA UNCLASSIFIED – Releasable to the PublicSystem
Driving Requirements and ConstraintsCoverageRepeatpassesOperations planning20%StereoPol SAR(30m resolution)20%HiRes SAR(6m resolution)2%Spotlight SAR(1m resolution)0.1%SRSGlobal- Night sideVenSpec-M & H60%- Night sideVenSpec-U50%- Day side- Observations on several consecutive orbitsRadio Science 50% with mostinterest in Southhemisphere-Power( Solar arrays andbattery)Orbit- roll-up max. 35deg.- angular baseline 1.4degReaction wheels,operationsInSAR(30m resolution)EnVision Slide 13min. 2Data volume(SSMM andcommunications)Constraints- roll-up max. 35deg.- roll-up max. 35deg.- roll-up max. 35deg.Antenna pointed to EarthNo maneuversAt least 6 hours tracking per day250-300km altitudeESA UNCLASSIFIED – Releasable to the PublicSystem
Areas of Most Interest for VenSAREnVision Slide 14ESA UNCLASSIFIED – Releasable to the PublicSystem
Expected Data ReturnTo fulfill all instruments data return requirements (related to coverage)a total of 278Tbits: 118Tbits (basic profile) 160Tbits (enhanced profiles) “Basic” mission profile: 118Tbits (123Gbits/day over mission duration –requirement is over at least two cycles)– InSAR, VenSpec, SRS and radio science (assumed in to communications) “Enhanced” mission profile(s): 160Tbits (to be spread over mission duration)– To fulfil the coverage requirements for StereoPol, HiRes and Spotlight SAR– HiRes and SpotLight SAR observations are mostly at the expense of VenSpec-UEnVision Slide 15ESA UNCLASSIFIED – Releasable to the PublicSystem
Additional Design Drivers Mission cost ceiling 550MEuros– Design to cost approach Launcher interface– Fairing max. diameter 4.570m– VenSAR antenna: 5.47m– HGA: 3m– SRS antenna: 16m (launched stowed) Launcher performance– Launch mass (depending on orbit)– Aerobraking is enabling the mission (chemical)EnVision Slide 16ESA UNCLASSIFIED – Releasable to the PublicSystem
Payload overviewESA UNCLASSIFIED – Releasable to the Public
Payload overview Scientific context of instruments VenSAR – synthetic aperture radar SRS – subsurface radar VenSpec – the spectrometer suite Radio Science – radio science experiment Resource budgets Follow-up tasksEnVision Slide 18ESA UNCLASSIFIED – Releasable to the PublicSystem
Detecting active geologic processes on Venus-past and todayMeasurementVenSpec-UMapping SO, SO2 and UV absorberat cloud top. @210-240nmHigher atmosphere (0.2nm), @190-380 (2nm), 100km spatial resolutionLower atmosphereVenSpec-HSurfaceVenSpec-MCrust profileSRSMapping of near surfaceatmosphere H2O, HDO at 0-15 km@1.08-1.2 µm, H2O, HDO, OCS,SO2 at 30-40 km @ 2.44-2.47 µm, 100 km spatial resolutionVenSARmapping mineralogy by surfaceemission at 6 channels 0.82-1.2µm at 50 km resolutionSubsurface radar down to1000 m depth and 10mresolution @ 9 MHzatmosphere, crust, RadioScienceplanet mantle and 2-way mapping, radio occultations,gravity field, love number k2coreEnVision Slide 19ESA UNCLASSIFIED – Releasable to the PublicSystemSurface morphology,1-30 m, cm changes byinter-ferometricmeasurements, @ 3.2GHz, radiometry withrelative precision of 1Kat 5x38 km resolution
VenSAR – Synthetic Aperture Radar 16-34VDC SUPPLY 16-35V Primary Power in(one of 18 individually switched)HIGH RATEDATA TOPLATFORMPLATFORMCMD/CTRLGPS1PPSPCMWIZARDLINK28 to 12VDC-DC28 to 5VDC-DC28 to 10VDC-DC28 to-12VDC-DC28 to 3.3VDC-DCOCXOx2CTG,DIGx2RF,CTGRFDIGVOLTAGE &CURRENTMONITORINGCTGCHIRPGENERATORPCU28 to 7V UBULKCHARGESTORAGECAPACITORS 7V BLE TRANSMITUNITMainTxBTx LORBUPLL/VCO3- ‐WAYPLL/VCODIGXilinx V5FPGADSP CHAIN2- P2HCalP2VCalLNA18- ‐wayRxCorporateFeedWIZRxLOThe instrument consists of 3 units SYNTHRXMS-band at 3.2 GHz (182 MHzbandwidth)ChargeControlMainTxAMUXADC The NIA backend x2 (cold redundant)The antenna unit incl. front end electronics,TX/RX and radiatorHarness 5.47m x 0.60m antenna (VenSAR) 300x270x220 mm backend end (2x) 254.4 -2352.0 W (different modes) 154 kg (no antenna structure, nodeployment device) Data rate 0.25 kb/s – 513 Mb/s Pointing (RPE) 300 arcsec 1000 sCTGClockTXMOCXO- ‐SPA synthetic aperture radarHeritage from NovaSAR-S (GaN hipower amplifiers), launched inSeptember 2018 28V18- ‐wayTxCorporateFeedTIMING& CONTROLGENERATORMUXDAC28 to 12V DC/DCI/OBUFFERSXilinx V5FPGAADCCHARGECONTROLCIRCUIT28 to 28V DC/DC LNAMainRxAMainRxBNIABack- ‐Endx2EnVision Slide 20x18ESA UNCLASSIFIED – Releasable to the PublicSystem
VenSAR – Synthetic Aperture RadarVenSAR uses 24 separatelycontrollable phase centres (6x4) Antenna length driven by imagingrequirements Reduction in length is not consistent with(low) pulse repetition frequency requiredby the swath width of 50 km. A shorterantenna illuminates a wider zone in alongtrack direction (ie wider Dopplerspectrum) which this PRF cannot sampleadequately. This would result in azimuthambiguities A narrower antenna would not deliverenough power through thick atmosphereresulting in too low S/N Chosen frequency is a goodcompromise between: H2SO4 droplet causes phase shift anddrives towards lower frequencies Too low frequency are less sensitive tosurface displacements Front surface coated by RFtransparent Ge-coated sunshield, innerside of the honeycomb panel coveredwith MLI to thermal isolate the unit fromthe S/C (NovaSAR-S approach) Implementing antenna supportstructure Implementing of folding mechanismEnVision Slide 21ESA UNCLASSIFIED – Releasable to the PublicSystem
SRS – Subsurface RadarPwrTxDCGCMDs,TLMsandDataSpWI/FCtrl RxA subsurface radar sounderHeritage from RIME (JUICE) 9 MHz with 6 MHz bandwidth Pwr Cond.DESEnVision Slide 22ADC RDSESA UNCLASSIFIED – Releasable to the PublicThe instrument consists of 4 units Receiver and digital subsystemTransmitterMatching networkDeployable antenna RDS (256x180x140 mm), TX(362x182x140 mm), MN(280x142x50 mm), antenna (16 m) 120.0 W (different modes) 12 kg (RDS/TX/MN) 14 kg antenna (CDF choice) Data rate 3.14 Mb/s – 12.6 Mb/s Pointing (APE) 5 degree RPE n/aSystem
SRS – subsurface radar antenna 16 m deployable boom, stowed 1.85 m Mass 14.4 kg Synchronized deployment Spring actuated first segment BeCu segments Preferred solution wrt to current RIME antennaheritage due to more challenging Venus thermalenvironment First assessment indicates compatibility toaerobraking and thermal load design has reached TRL4EnVision Slide 23ESA UNCLASSIFIED – Releasable to the PublicSystem
VenSpec – The Spectrometer SuiteEnVision Slide 24 Suite of spectrometers Strong heritage from various precursormission Physically separated instrument boxes,controlled by a single control unit (CCU) Total mass 31.63 kg Power 45.2 W -M (590x215x204 mm)-H (380x144x173 mm)-U (500x200x200mm)-CCU (200x200x200mm) ESA UNCLASSIFIED – Releasable to the PublicVenspec-MVenSpec-HVenSpec-UCCUSystem
VenSpec –M Pushbroom multispectral imaging system, nadir pointing Telecentric design with 3 lenses FOV of 45 results in 207km swath width, 50 km spatial res. 14 strip filter array at intermediate focus, covering all 5surface windows between 0.8 and 1.2 µm APE 1 mrad, RPE 0.5 mrad over 90 msec Camera including optics and detector Baffle functionally dedicated to the camera includingthe transparent window unit Electronics including PCB’s for power supply andinstrument control and internal harness InGaAs detector by Xenics with TEC Heritage from Mertis and breadboardingAccommodation itemMass (kg) CBE/CBE contingencyPower (W) CBE/CBE contingencyPeak (Science, Test, Diagnostic, Science idle modes)Average (Science, Test, Diagnostic, Science idlemodes)Standby (Diagnostic safe mode)Dimensions (mm3) Incl. baffleInstrument body5.00/5.8515.0/19.511.5/15.08.0/10.5590 215 204380 144 173Data interface/ rate46.4 37.8 SpaceWire, 500kb/s8Data rate (kpbs) 33 33, 5 5 binning190, 850Effective focal length (mm)16.4Data rate, raw (kbps)4500F/#2.04Temperature range ( C) Operational / NonoperationalOpticsDesign ParameterValueFOV ( ) ACTxALT46.4 37.8Entrance pupil diameter (mm)EnVision Slide 25Unobstructed FOVValueESA UNCLASSIFIED – Releasable to the PublicSystem0 to 35 / -20 to 50
VenSpec-HEnVision Slide 26 1.08-1.2 µm @ R 20002.44-2.47 µm @ R 40000Heritage SPICAV-SOIR/VEX, NOMAD/TGO19.17 kg, 21.74 W Data rate 37 kb/sAPE 3.5 mrad, RPE 3.0 mrad over 60 secNadir pointing, 100 km spatial res.ESA UNCLASSIFIED – Releasable to the Public a hi-res infrared Echellespectrometer with AOTF (tbc) Sofradir HgCdTe detector in amodified integrated detector dewarcooler assembly (detectortemperature at 150 k)System
VenSpec-U Dual channel UV spectral imager, nadir Low-res 190-380nm, hi-res 210-240 Spectr. res. 1.5 nm and 0.2 resp. Heritage from SPICAM/Mex, SPICAV/Vexand PHEBUS/BepiC Mass 4.11 kg, 14.4 W, data rate: 20 kb/s 100km spatial resolution APE 10 mrad, RPE 1 mrad over ½ orbitEntrance objectiveFocal lengthF-#Front lens diameter2 aspheric lenses, UV gradefused silica25.14mm1050mmDetectorCustomized CMOS CAPELLA2nd generation from Teledyne/E2V with innovative “AR” UVcoatingUseful area [mm²]24 (spatial) 12 (spectral)Pixel sizeFull well chargeReadout noisePower [W]40µm 40µm45 ke 6e4EnVision Slide 27ESA UNCLASSIFIED – Releasable to the PublicPHEBUSonBepiColomboSystem
VenSpec – CCUTwo subunits EnVision Slide 28 data handling unit (DHU) power handling unit (PHDU) Partial heritage from MERTIS/BepiC and Cheops 200x200x200 mm 2.5 kg (incl 50% margin)ESA UNCLASSIFIED – Releasable to the PublicSystem
Radio Science – The Gravity Experiment Radio-navigation tracking data, relying on the spacecraft TT&C system No additional H/W required 2-way tracking x-band up / x-band down, x-up /Ka-band down Observations during communication paths Experiment requirement 4 successive orbits per day Gravity field measurements to cover 100% of the planet Coverage better than 50% at spatial resolution better than 200 km Scientifically more interesting region on the southern hemisphere Current S/C sub-system performance matches requirements ESTRACK reaching an accuracy of at least 0.1 mm/sec (including all errorcontributors, like troposphere, clocks, station coordinates knowledge, solarplasma and more), when integrating the Doppler observable over a countinterval of 60 seconds. parasitic deltaV after wheel offloading 0.2 mm/s, measurements also duringwheel offloading sequenceEnVision Slide 29ESA UNCLASSIFIED – Releasable to the PublicSystem
Top level requirements – Resource Budgets(incl. support equipment)VenSARRadioScienceVenSpecSRSMass154 kg22.56 kg (support)22.40 kg (deployment)Experiment,no H/W31.6310.014.4 (antenna)Σ 254.99 kg(incl. instrumentmaturity margin)Power254-2352(InSAR: 641-977)--45.251202352 W max(sequencedoperations)Volume300x270x220(backend x2)5470x600(antenna/front CCU)Data rate(nominal)0.25 kb/s – 513 Mb/s(no compression)---H 37 kb/s-U 20 kb/s-M 500 kb/s(differentcompressionfactors)EnVision Slide 30(-M)(-H)(-U)(-256x180x140 (RDS)362x182x140 (TX)280x142x50 (MN)16000 (2x8000)(ant.)3.8 Mb/s (low res.compressed)ESA UNCLASSIFIED – Releasable to the PublicSystem
Next steps in (pre)-industrial phase Accommodation SRS antenna orientation to be re-assessed position of VenSpec-H wrt cold face during entire operations to be assessed, thermally analysed on S/C level andinstrument level all spectrometer straylight analysis Slanted SAR accommodationOperations In principle surface/atmospheric coverage requirements are achieved but require optimisation VenSAR spotlight and SRS high res. coverage is on the low side, VenSpec-U observation time is short due to VenSARoperationsImplications of frozen eccentricity orbit to be further analysed by RadioScience, VenSAR, VenSpec, SRSproposed is a task force of SEWG/SST and ESA until industrial KO, boundary conditions distributed by ESA, regularteleconfs throughout this phase with science/ instrument consolidation workshopThermal environment and aerobraking more detailed work on
– EnVision, to determine the nature and current state of geological activity on Venus, and its relationship with the atmosphere, in collaboration with NASA – SPICA, the Space Infrared observatory for Cosmology and Astrophysics using a 2.5 m cryogenic telescope, in collaboration with JAXA
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