•Several successive observations of the celestialsphere enable to measure relative motionsbetween stars, but in 2D => 2D dynamicsmapping•Radial distance and radial velocity (along observer line ofsight) are missing to complete a complete 3 D dynamicsmeasurement Radial distance: Parallax measurement Radial velocity: Doppler effect (light spectrum of astar is shifted toward blue (short wavelength) whenstar is coming closer and shifted to the red whenstar is moving away)=> spectrometry
p4Gaia main objectiveImprove star positioningknowledge by a factor 100,stars up to magnitude 20Observe more than one billion of objects, without any a priori Position => astrometry + chromaticity correction Distance => astrometry Proper motion => astrometry + HR spectrometry Physical properties => photometry + HR spectrometry=> 3 instruments on board the spacecraft
p61,5 millions km far away from EarthThere are 5 equilibrium positionsfor a 3 body system, one of thembeing provided with a marginalmass. Soleil+Earth+spacecraftLagrangian point L2 is wellsuited for cosmos observation= Stability
16 years from concept to launchProposalConcept & Technology StudyMission SelectionRe-Assessment StudyPhase B1Scientific operationLaunch 2013FinalStudiesData ProcessingImplementationData ProcessingDefinitionOperationMission ProductsIntermediateSelection of Prime Contractor (EADS Astrium SAS)Phase B2Phase C/DSoftware Development (DPAC)
p83 instruments sharing the same focalplane• Photometry & RVS: spectral dispersion is produced in the imagespace, in front of the focal plane => common detection & processing Blue & red photometrywith 2 prisms in the FPA& dedicated CCDs: Chromaticity correctionsimultaneous to astrometry Medium Band Photometry[330-1000 nm] Radial Velocity Spectrometerwith grating & afocal corrector& 12 dedicated CCDs: Spectrometry in [847-874nm] Radial Velocity measurement
p11Two telescopes combined on the samefocal plane • 2 Three Mirror Anastigmat telescopes M1-M3aperture 1450x500 mm², focal length f = 35 mangular separation = basic angleCommonfoldingmirrorsM1M3M2M1M3M2M4M’4M1M3M4 - beamcombinerM2 Intermediate image used for field discrimination Beam combiner at their exit pupil => common FPAM’1M1 LOS 2LOS 1M’2M2M3M’3M4/M’4(combiners)M5M6CommonFPALOS1LOS2M1M2M3M’1M’2M’3Beam combinerCommonFPA
p12A stable opto-mechanical design• Full silicon carbide architecture• Passive thermal design• Decoupling by release of launchbipodsM’3M’2M1M’1FPA withradiatorsIsostaticmountsPLMopticalbenchFolding optics structurewith RVS opticsM5M6M’4M4(CDR design status)
30/07/2010 Service Module (SVM) arrival in ToulouseCarbon fiber structure (made by CASA, Spain), Propulsionelements (CPS system made by ASTRIUM UK, and part ofMPS system made by TAS Italy), electrical harness (CASA),previously assembled and tested in Stevenage (UK)22/10/2010, first switch ON of the SVM electrical firstequipments : power, calculator, interfaces and first centralsoftwareOctober 2011, the SunShield (DSA) is delivered by SENER (Spain)
Autumn 2011 : Mechanical testsVibrations, acoustics noise are simulated to the Spacecraft to verify if thestructure and the differents fixations could resist to the future launchThe missing equipments are simulated by loads (for example, thePayload). The tanks are full of Helium, Nitrogen or Isopropylic alcohol tosimulate the future propellant gaz.Beginning of 2012, new DSA deployment to verify if it passed successfully the mechanical tests = successful launch
Test de vibrations mécaniquesBeginning 2012 : mechanical tests of the PayloadAcceleration up to 10G !
April 2012, delivery of the Phase Array AntennaThis antenna will allowed to send the data recorded on board to the EarthA new step to the complete Spacecraft !
Summer 2012, SVM Thermal VacuumWith captors inside, the SVM is placed into a vacuum chamberto simulate the temperature into Space. The objectives is toverify that all the equipments are well running onto vacuum andthat thermal predictions are confirmed.December 2012, Payload Thermal VacuumThe performance of the 3 instruments are verify in vaccum andlow temperature (stability, good images, …)
February 2013 Payload deliveryGAIA became a complete satellite !In order to avoid any contamination on mirrors and CCD, theassembly is done in a class 100 clean room (less than 10000particles of 0,1µm or less than 30 particles of 1µm in 1m3 air).
March 2013, beginning of the final verificationsThe spacecraft is measured : weight, Center of gravity, inertiamoment
EMC TEST in anechoic chamberVerification that all equipmentsare not « noisy » to others, inparticular the PAA
Automn 2013: launch on Soyouz from Kourou, french Guyana
Key Numbers Mass spacecraft at launch : 2 100 kg Mass propellant : 300 kg Diameter of the Sunshield in orbit configuration : 10 m Primary mirrors : 1.45 m x 0.5 m Focal Distance : 35 m CCD : 1 Gpixels @ 160 K Mass memory : 1 Tb Science Telemetry : 10 Mbits/sWith about 100 Go of data each day, 1 Peta-octet (1000 To)of data at the end of the GAIA mission !
News about GAIA on my blog :http://idariane.wordpress.comOn ESA page :http://sci.esa.int