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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. Scopo di LISA PAthfinder. Sensitivity of LISA.

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LISA PathfinderPreventivi2013 Gruppodi Trento

Principalinvestigator 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

Scopo di LISA PAthfinder

Sensitivityof LISA

Laser link

Laser link

  • Soppressionedelleaccelerazioniparassite a megliodi 3×10-14 ms-2√Hz

  • (10 volte menostringentedi LISA)

LISA PF a Trento

LISA PF in Europa


Laser modulator


Co - PI, LTP Architect (Astrium), Laser


PI, Inertial Sensor (ISS), Caging Mechanism




Data Diagnostics System, Data Management Unit


ISS Front End Electronics

United Kingdom:

Optical Bench, Phase-meter, Charge


LISA PF in Italia

Collaborazione INFN LISA PF

AQ, FI, NA,RM2 eTN: circa 30 persone (19 FTE)


Principalinvestigator della missione LISA Pathfinder

  • ----- Il monitoraggio dello sviluppo del programma e delle prestazioni

  • -----Attività di “shadowengineering” :

    • supporto all’indagine/soluzione delle non-conformances riportate sull’hardware consegnato

  • ------ Supporto alla missione:

    • sostegno alla MissionCritical Design Review, supporto all’analisi degli aspetti critici della missione

  • ------ Sviluppo dell’esperimento in orbita e dell’analisi dati

  • ------Sviluppo dei tool di analisi dati: nel 2012 Release 3.0 del software di analisi dati LTPDA

  • ------ Preparazione delle operazioni di LISA PF

Testing a terra del sensore gravitazionale

con pendoli di torsione

Testing a terra della fase di rilascio in volo della test mass

  • Stato di avanzamento di LISA Pathfinder

  • LTP status: allpartsdelivered and workingtospecsexceptsfor:

  • - EH repairingactivityunderway (guardringdetachmentduringvibration test)

  • - Charge management sistemunderperforming: fix under finalisation

  • TM launchlock: foundtechnicallyfeasiblesolutions; CDR isunderway.

Science Module: H/W complete - except

-LTP Coreassembly

-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.

  • 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.


GRS on groundtestingwithtorsionpendulum

GRS prototypes and LPF-like Test Masses :

increasing representativeness



4 mm gaps,

LPF geometry

Mo / Shapal EM

LPF FM-replica

Mo / Sapphire LPF EM

LPF-like TM

nmroughness !

Lightweight : empty TM in goldcoated Al

Same FM TM finishing

  • GRS on groundtestingwithtorsionpendulums

    Results 2011-2012

  • GRS Flight Model Replica and 4 mass pendulum:

  • Studyof UV discharge performance afterbakeout at 110° C completed , demonstratingmarginal performance (stillallows “useasis” in flight)

  • Testsofdcstrayelectrostaticbias, temperature gradienteffects (radiometer, radiationpressure, temperature dependetoutgassing), and Browniannoisecompleted: alleffects are withinrequirements

  • GRS prototype and 1 mass pendulum (high sensitivitypendulum):

  • Experimentalinvestigationof TM chargeinteractionwithstrayelectrostaticfields inside GRS

  • with upper limitsbelowfor the surfacepotentialfluctuations 12 mV/Hz1/2 between 5 cm2 patches on a Au surface at 1 mHz

  • Refinedtechniquefordirectlymeasuringstray DC fieldcouplingto TM charge in flight on LPF / LISA

  • [PRL 108, 181101 (2012)]

  • Measurementofelectrostaticdissipation in nominally-vacuum gap capacitors inside GRS

  •  detection oftransientforcesassociatedwithdissipation at 10-17 Nmlevel

  • meausuementof loss angle d ≈ 3 10-7 for 2 electrodepairs, consistentwithfrequencyindependent loss model

  • sufficientlysmallfor LISA

  • Developmentofnrad-interferometricangularreadoutfortorsionpendulum

  • Bench top preliminary (in air) measurementswithinfactor 10 of goal

  • Vacuumtesting and pendulumintegrationupcoming

  • GRS on groundtestingwithtorsionpendulums

  • Activity 2012-2013

  • Torsionpendulumupgrades: integrationofnew (1 TM) torsionpendulumwithinterferometricangularreadout

  • (willallowformeasurementofforcenoisefrom GRS at levelsbeyond LPF goal and Improvedmeasurementofstraypotentialfluctuations)

  • Completionof test campaignwithcurrent-baselineflight-model GRS Flight model replica + flight-representative TM (upper limitof the overallforcedisturbanceform the GRS)

  • Integration in the 4 TM pendulumof a new TM withAuPtinserts+ GRS with the samecleaning procedure of the FilghtModel ( particularlyrelevantfor the UV discharge procedure performances)

  • Supportfordefinition / testingof LPF flight measurementsequence (including free fall mode)

  • and associated data analysisproceduresusing LTPDA toolbox

On ground Test Mass releasetesting

  • Attività gennaio-giugno 2012

  • Misura del trasferimento di quantità di moto utilizzando l’attuatore 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 d’oro o in presenza di coating antiadesivo

  • Attività previste 2012-2013

  • Misura del trasferimento di quantità di moto utilizzando l’attuatore attualmente a disposizione (PILine)con il mock-up pesante (1kg) di test mass impiegando inserti Au/Pt privi di coating d’oro o dotati di coating antiadesivo

  • Misura del trasferimento di quantità di moto installando il GPRM nella facility.

The Test Mass release testing

  • 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

Composizione LISA PF Trento

Richieste 2013 (preliminare)

Nessuna richiesta ai Servizi


LPF GRS replica afterbake-out at 110 C






Slope affected by the accuracy of the Ion P gauge, which is nominally 15%

Closeto the expected @293 K

@ P=2e-8 mbar

Radiometer 23 pN/K  5 pN/K

T dependentOutgassingprobablydominates

Brownian noise

LPF FM-replica

Same FM TM finishing

The GRS contributionisobtainedasdifferencebetweenthisvalue and the simulatedonefor 4TM pendulumwithout GRS

Simulationwithout GRS

Random TM chargingandDCstraypotential: LISA Pathfinder GRS replica

Compensazione dcbias
































compensationto <1 mVdemonstrated

Error due toshearforcecompensationnotpresentwith TM charge, orderof 10 mV controlwithreal TM chargevariation

Interactionofstrayelectrostaticfields and TM charge

  • Upper limits on surfacepotentialfluctuations

  • < 12 mV/Hz1/2 at 1 mHz on 5 cm2 Au surfaces

  • < 2 fm/s2/Hz1/2for LISA /LPF TM

  • Directmeasurementofstray DC fieldcouplingtonoisy TM charge

  • refinesin-flighttechniquetonullingsurfacepotentialdifferencesto < 1 mV


Thermodynamicforcenoise source for LISA and experimentalgravitation




  • Squarewavemodulationtechnique, 10-17Nmtransienttorqueresolution

  • Detect loss angle d≈ 3 10-7for 2 electrodepairs smallenoughfor LISA!

  • Waveform and distancedependenceconsistentwithdindependentoffrequency

Angularinterferometer: nrad/Hz1/2 sensingforsub-fNforce detection


  • Status:

  • Workingheterodynemodulationbench, homemadephasemeter, and single bounceMach-Zehnder IFO

  • In vacuumrotationalnoise test summer 2012, torsionpendulumintegrationFall-Winter 2012-2013






“Rotation cancelling” phasecombination

  • Test performed exploring different directions of retraction searching the maximum impulse

  • With 100g TM dummy the max measured impulse is 3.5×10-5N*s (3.5 times the requirement)

  • Possible margin hidden by the “slow” tip retraction performed in the experiment wrt the GPRM

Grabbing Positioning and Release Mechanism (GPRM)

Impulse (N*s) vs. tiporientation

Impulse (N*s) vs. tiporientation

  • 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