Spacecraft development

Gaia functionalarchitecturePayload ModulePLM Thermal Passive HardwareTimingPayloadDataHandling VPUUnitVPUSpWSpWSpWSpWSpWVPUVPUVPUVPUVPUVPUVPUVPUVPUVPUFocal Plane AssemblyLEGENDStructure optical assemblyVPUSpWVPUVPUInternally redunded unitRedundant unitLaunch bipodsSpWVPUVPUPLM unitsElectrical SVM unitsBasicAngleMonitorWaveFrontSensorM2mechM’2mechPLM units on PLMCDMS unitsClockDistributionCDUUnitBAM & WFSBAM & WFSsourcesourceelectronicselectronicsM2 mirrorsM2 mirrorsmechanismmechanismdrive electronicsdrive electronicsPLM units on SVMAOCS unitsElectrical SVMTimingPkWPayload MIL-STD 1553 busElectrical power unitsTT&C unitsLow GainAntennasystemPhased ArrayAntennaSSPAX-Rx X-RxX-Tx X-TxSpWTransponderTRSPLVDSControl andDataManagementUnitSpWElectricalInterfaceUnitI/O’sSSPASSPAMechanical SVM unitsLinksSVM MIL-STD 1553B busMicropropulsion unitsChemical propulsion unitsSolar arraysSVM MIL-STD 1553 busPLM MIL-STD 1553 busSpace Wire/Packet WireTiming & datationDeployableSunshieldAssemblyThermal tentSolararraysPowerConditioning&DistributionUnitBattery28 VtousersPyropulsesFineFineSunFineSunSensor SunSensorSensorStarTrackerSTREGyrosGyrosGyrosChemical propulsionThermalHeaterssensorsSVM ThermalPassive HardwareDSA, thermal itemsRF signalStructure SVMMechanical SVMMicroPropulsionElect.STRESTREMicropropulsionMicroPropuslionAssemblySTRESTREDynamic and control Design approach‣ 1st step• Considering the required attitude profiles and disturbing torque assessments:– Selection of control concept: passive or active, spinned or 3 axis controlled– Gaia: slow rotation with precession: 3 axes control• Considering the spacecraft configuration and the disturbing torque assessment– Selection of the control (thrusters, micro thrusters, reaction wheels, control momentum gyros…)– Gaia: ultimate stability required: micro thrusters‣ 2nd step• Selection of sensors• Actuator sizing and control bandwidth definition• Gaia– Hybridizing instrument (stability) and star tracker (inertial attitude) in normal mode– Fine sun sensor and gyros for initial acquisition and safe mode– Hybridizing high accuracy gyros/ start tracker for intermediate mode.‣ 3rd step• AOCS modes definition, associated control laws• Definition of failure modes and associated recovery procedures• Pointing budget elaboration, resources budgets (propellant, processing…)