Presentazione sul tema: "LISA Pathfinder Preventivi 2013 Gruppo di Trento Principal investigator della missione LISA Pathfinder Testing a terra del sensore gravitazionale con pendoli."— Transcript della presentazione:
LISA Pathfinder Preventivi 2013 Gruppo di Trento Principal investigator della missione LISA Pathfinder Testing a terra del sensore gravitazionale con pendoli di torsione Testing a terra della fase di rilascio in volo della test mass Padova, 09/07/2012 1
Scopo di LISA PAthfinder Laser link Soppressione delle accelerazioni parassite a meglio di 3×10 -14 ms -2 Hz (10 volte meno stringente di LISA) Sensitivity of LISA Padova, 09/07/2012 2
LISA PF a Trento France: Laser modulator Germany: Co - PI, LTP Architect (Astrium), Laser Italy: PI, Inertial Sensor (ISS), Caging Mechanism Netherlands: ISS SCOE Spain: Data Diagnostics System, Data Management Unit Switzerland: ISS Front End Electronics United Kingdom: Optical Bench, Phase-meter, Charge Management LISA PF in Italia Collaborazione INFN LISA PF AQ, FI, NA,RM2 eTN: circa 30 persone (19 FTE) LISA PF in Europa Padova, 09/07/2012 3
ATTIVITA DEL GRUPPO di TRENTO Principal investigator della missione LISA Pathfinder Testing a terra del sensore gravitazionale con pendoli di torsione Testing a terra della fase di rilascio in volo della test mass ----- Il monitoraggio dello sviluppo del programma e delle prestazioni ----- Attività di shadow engineering : supporto allindagine/soluzione delle non-conformances riportate sullhardware consegnato ------ Supporto alla missione: sostegno alla Mission Critical Design Review, supporto allanalisi degli aspetti critici della missione ------ Sviluppo dellesperimento in orbita e dellanalisi dati ------ Sviluppo dei tool di analisi dati: nel 2012 Release 3.0 del software di analisi dati LTPDA ------ Preparazione delle operazioni di LISA PF Padova, 09/07/2012 4
Stato di avanzamento di LISA Pathfinder LTP status: all parts delivered and working to specs excepts for: - EH repairing activity underway (guardring detachment during vibration test) - Charge management sistem underperforming: fix under finalisation -TM launch lock: found technically feasible solutions; CDR is underway. -In 2011 a quite important test of all the optical metrology integrated into the complete spacecraft (except for the inertial sensor) and within a full space simulator, has been performed. The test has been a success. Padova, 09/07/2012 5 LANCIO NEL 2014 Science Module: H/W complete - except -LTP Core assembly -Micro-propulsion system: identified more that one viable alternatives, including a cold- gas based one with off-the-shelf maturity that is now the likely adopted baseline. Final decision in 2012.
GRS on ground testing with torsion pendulum Padova, 09/07/2012 6
Mo / Shapal EM Mo / Sapphire LPF EM GRS prototypes and LPF-like Test Masses : increasing representativeness Padova, 09/07/2012 7 Lightweight : empty TM in gold coated Al GRS 4 mm gaps, LPF geometry LPF-like TM nm roughness ! LPF FM-replica Same FM TM finishing NOW !
GRS on ground testing with torsion pendulums Results 2011-2012 GRS Flight Model Replica and 4 mass pendulum: Study of UV discharge performance after bakeout at 110° C completed, demonstrating marginal performance (still allows use as is in flight) Tests of dc stray electrostatic bias, temperature gradient effects (radiometer, radiation pressure, temperature dependet outgassing), and Brownian noise completed: all effects are within requirements GRS prototype and 1 mass pendulum (high sensitivity pendulum ): Experimental investigation of TM charge interaction with stray electrostatic fields inside GRS with upper limits below for the surface potential fluctuations 12 mV/Hz1/2 between 5 cm2 patches on a Au surface at 1 mHz Refined technique for directly measuring stray DC field coupling to TM charge in flight on LPF / LISA [PRL 108, 181101 (2012)] Measurement of electrostatic dissipation in nominally-vacuum gap capacitors inside GRS detection of transient forces associated with dissipation at 10-17 Nm level meausuement of loss angle d 3 10-7 for 2 electrode pairs, consistent with frequency independent loss model sufficiently small for LISA Development of nrad-interferometric angular readout for torsion pendulum Bench top preliminary (in air) measurements within factor 10 of goal Vacuum testing and pendulum integration upcoming Padova, 09/07/2012 8
GRS on ground testing with torsion pendulums Activity 2012-2013 Torsion pendulum upgrades: integration of new (1 TM) torsion pendulum with interferometric angular readout (will allow for measurement of force noise from GRS at levels beyond LPF goal and Improved measurement of stray potential fluctuations) Completion of test campaign with current-baseline flight-model GRS Flight model replica + flight-representative TM (upper limit of the overall force disturbance form the GRS) Integration in the 4 TM pendulum of a new TM with AuPt inserts+ GRS with the same cleaning procedure of the Filght Model ( particularly relevant for the UV discharge procedure performances) Support for definition / testing of LPF flight measurement sequence (including free fall mode) and associated data analysis procedures using LTPDA toolbox Padova, 09/07/2012 9
On ground Test Mass release testing Attività gennaio-giugno 2012 Misura del trasferimento di quantità di moto utilizzando lattuatore attualmente a disposizione (PILine)con i mock-up intermedio (100g) e pesante (1kg) di test mass. Elaborazione dei dati sperimentali raccolti al fine di ricavare la legge forza-elongazione del legame adesivo Lavorazione di inserti Au/Pt con morfologia superficiale rappresentativa del recesso piramidale della test mass di volo per successive prove di trasferimento di quantità di moto in assenza di coating doro o in presenza di coating antiadesivo Attività previste 2012-2013 Misura del trasferimento di quantità di moto utilizzando lattuatore attualmente a disposizione (PILine)con il mock-up pesante (1kg) di test mass impiegando inserti Au/Pt privi di coating doro o dotati di coating antiadesivo Misura del trasferimento di quantità di moto installando il GPRM nella facility. Padova, 09/07/2012 10
The Test Mass release testing Padova, 09/07/2012 The Grabbing Positioning and Release Mechanism (GPRM) is designed to hold and release the TM into free fall. The release is performed by quick retraction of two tips. The TM may be captured by the capacitive actuation system if its residual velocity after release is less than 5 micron/s (10 -5 Ns impulse). Gold coated surfaces (tip/TM) develop strong adhesive bonds. Adhesion between the tips and the TM produces a pull (a momentum transfer) during release. The verification of the requirement of residual velocity is part of the LISA PF ground testing activities. The Transferred Momentum Measurement Facility is developed to characterize the TM release velocity 11
Richieste 2013 (preliminare) Nessuna richiesta ai Servizi Composizione LISA PF Trento Padova, 09/07/2012 12
Thermal gradient related forces: Radiometer Radiation pressure Temp dependent outgassing LPF GRS replica after bake-out at 110 C Slope affected by the accuracy of the Ion P gauge, which is nominally 15% T(K) Slope (N/K/mbar) stat. error (N/K/mbar) Intercept (pN/K) stat. error (pN/K) 289.202.47e-42e-6263 295.462.39e-43e-6361 304.302.75e-44e-6534 Close to the expected @293 K @ P=2e-8 mbar Radiometer 23 pN/K 5 pN/K T dependent Outgassing probably dominates Padova, 09/07/2012 14
Brownian noise LPF FM-replica Same FM TM finishing The GRS contribution is obtained as difference between this value and the simulated one for 4TM pendulum without GRS Simulation without GRS Padova, 09/07/2012 15
Compensazione dc bias Random TM charging andDC stray potential: LISA Pathfinder GRS replica Force +Veq -Veq Force +Veq -Veq +Veq-Vcomp=0 -Veq+Vcomp=0 +Veq-Vcomp=0 -Veq+Vcomp=0 -Vcomp +Vcomp Force -Vcomp +Vcomp compensation to <1 mV demonstrated Error due to shear force compensation not present with TM charge, order of 10 mV control with real TM charge variation Padova, 09/07/2012 16
Interaction of stray electrostatic fields and TM charge Upper limits on surface potential fluctuations < 12 V/Hz 1/2 at 1 mHz on 5 cm 2 Au surfaces < 2 fm/s 2 /Hz 1/2 for LISA /LPF TM Direct measurement of stray DC field coupling to noisy TM charge refines in-flight technique to nulling surface potential differences to < 1 mV Padova, 09/07/2012 17
Experimental investigation of electrostatic dissipation Thermodynamic force noise source for LISA and experimental gravitation vnvn V Stochastic surface potential fluctuations from surface dissipation mixes with static potential differences to give force noise Squarewave modulation technique, 10 -17 Nm transient torque resolution Detect loss angle 3 10 -7 for 2 electrode pairs small enough for LISA! Waveform and distance dependence consistent with independent of frequency Padova, 09/07/2012 18
Angular interferometer: nrad/Hz1/2 sensing for sub-fN force detection Bench-top development Status: Working heterodyne modulation bench, homemade phasemeter, and single bounce Mach-Zehnder IFO In vacuum rotational noise test summer 2012, torsion pendulum integration Fall- Winter 2012-2013 1 2 3 4 Rotation cancelling phase combination Preliminary in-air noise measurements Padova, 09/07/2012 19
Padova, 09/07/2012 Impulse (N*s) vs. tip orientation Test performed exploring different directions of retraction searching the maximum impulse With 100g TM dummy the max measured impulse is 3.5×10 -5 N*s (3.5 times the requirement) Possible margin hidden by the slow tip retraction performed in the experiment wrt the GPRM Extrapolation to in-flight release made with the identified mathematical model of the mechanism shows compliance with the requirement (2.6 margin factor) Due to the criticality of the release, the testing of the GPRM EQM in the TMMF is foreseen for improved representativeness Grabbing Positioning and Release Mechanism (GPRM) Impulse (N*s) vs. tip orientation 20
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