1

LISA PathfinderPreventivi 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

2

Scopo di LISA PAthfinder

Laser

link

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

3

LISA PF a TrentoRICERCATORIDolesi Rita associato Ricercatore 90Giuliana Russano associato Dottoranda 100Vitale Stefano associato Prof. Ordinario 80Weber William associato Ricercatore 90Antonucci Federica associato Assegnista 100Tu Hai Bo associato Assegnista 100Congedo Giuseppe da associare Assegnista 100Ferroni Valerio da associare Assegnista 100Wen Shyang da associare Assegnista 100Cavalleri Antonella da associare Ricercatore (CNR FBK) 90

Tot RICERCATORI (FTE) 9,5

Hueller Mauro Non associabile Co Co Co 50

TECNOLOGIBenedetti Matteo associato Ricercatore 40Bortoluzzi Daniele associato Prof. Associato 70Bosetti Paolo associato Ricercatore 10Cristofolini Ilaria associato Ricercatore 10De Cecco Mariolino associato Prof. Associato 10Da Lio Mauro associato Prof. Ordinario 10Mezzena Renato associato Tecnologo E.P. 10

Tot TECNOLOGI (FTE) 1,6Tot TECNOLOGI (FTE) >10% 1,1

France:Laser modulator Germany: Co - PI, LTP Architect (Astrium), LaserItaly: PI, Inertial Sensor (ISS), Caging MechanismNetherlands: ISS SCOESpain: Data Diagnostics System, Data Management UnitSwitzerland:ISS Front End ElectronicsUnited Kingdom: Optical Bench, Phase-meter, Charge Management

LISA PF in ItaliaCollaborazione INFN LISA PFAQ, FI, NA,RM2 eTN: circa 30 persone (19 FTE)

LISA PF in Europa

Padova, 09/07/2012

4

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 all’indagine/soluzione delle non-conformances riportate

sull’hardware consegnato

------ Supporto alla missione: • sostegno alla Mission Critical 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

Padova, 09/07/2012

5

Stato di avanzamento di LISA PathfinderLTP 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

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.

6

GRS on ground testing with torsion pendulum

TM

Autocollim ator beam

X sensing electrodes

shaft

fiber

Padova, 09/07/2012

7

Mo / Shapal EM Mo / Sapphire LPF EM

GRS prototypes and LPF-like Test Masses :

increasing representativeness

Padova, 09/07/2012

Lightweight : empty TM in gold coated Al

GRS4 mm gaps,

LPF geometry

LPF-like TM

nm roughness !

LPF FM-replica

Same FM TM finishing

NOW !

8

GRS on ground testing with torsion pendulumsResults 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

9

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

10

On ground Test Mass release testing

 

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.

Padova, 09/07/2012

11

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

12

Richieste 2013 (preliminare)Nessuna richiesta ai Servizi

RICERCATORIDolesi Rita Ricercatore 90Giuliana Russano Dottoranda 100Vitale Stefano Prof. Ordinario 80Weber William Ricercatore 90Antonucci Federica Assegnista 100Tu Hai Bo Assegnista 100Congedo Giuseppe Assegnista 100Ferroni Valerio Assegnista 100Wen Shyang Assegnista 100Cavalleri Antonella Ricercatore (CNR FBK) 90

Tot RICERCATORI (FTE) 9,5

Hueller Mauro Co Co Co 50

Composizione LISA PF Trento

Missioni 8000Consumo Ricerca 9000Manutenzione 6000

I nventariabile (pompa turbo 400 l/s, lettore di pressione calibrato, RGA, 4 controller per motor, posizionatore lineare piezoelettrico) 33000Costruzione apparati (specchi per interferometro e per pendoli, refurbishment GRS Replica) 30000Totale Richieste 2013 86000

Cavalleri Antonella

TECNOLOGIBenedetti Matteo Ricercatore 40Bortoluzzi Daniele Prof. Associato 70Bosetti Paolo Ricercatore 10Cristofolini Ilaria Ricercatore 10De Cecco Mariolino Prof. Associato 10Da Lio Mauro Prof. Ordinario 10Mezzena Renato Tecnologo E.P. 10

Tot TECNOLOGI (FTE) 1,6Tot TECNOLOGI (FTE) >10% 1,1

Padova, 09/07/2012

13Padova, 09/07/2012

EXTRA

14

Thermal gradient related forces:

2

04

03

0

05

20

03

00

2931034.1

)(40293

2729310

18

)(38

4)(

TK

KsnJTQ

KpN

KTk

KpN

TK

PaPk

KpN

TTAQT

ck

TPAk

TddF

rpR

rpRx

x Radiometer

Radiationpressure Temp dependent

outgassing

LPF GRS replica after bake-out at 110 C

0 0.5 1 1.5 2 2.5x 10

-6

0

1

2

3

4

5

6

7 x 10-10

dFor

ce/d

T (N

/K)

Pressure (mbar)

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)

289.20 2.47e-4 2e-6 26 3295.46 2.39e-4 3e-6 36 1304.30 2.75e-4 4e-6 53 4

Close to the expected @293 K

@ P=2e-8 mbar

Radiometer 23 pN/K 5 pN/KT dependent Outgassing probably dominates

Padova, 09/07/2012

15

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

16

Compensazione dc bias

Random TM charging andDC stray potential: LISA Pathfinder GRS replica

mHz 1 /s1000mV 10

fN/Hz 2.02 2/1

1/22

2/1 fxC

Ce

S EFFxx

T

EFFF

ForceForceForceForce

+Veq

+Veq

-Veq

-Veq

Force

+Veq

+Veq

-Veq

-Veq

+Veq-Vcomp=0

+Veq-Vcomp=0

-Veq+Vcomp=0

-Veq+Vcomp=0

+Veq-Vcomp=0

+Veq-Vcomp=0

-Veq+Vcomp=0

-Veq+Vcomp=0

-Vcomp

-Vcomp

+Vcomp

+Vcomp

ForceForce

-Vcomp

-Vcomp

+Vcomp

+Vcomp

compensation to <1 mV demonstratedError due to shear force compensation not present with TM charge,

order of 10 mV control with real TM charge variation Padova, 09/07/2012

17

Interaction of stray electrostatic fields and TM charge

Upper limits on surface potential fluctuations• < 12 mV/Hz1/2 at 1 mHz on 5 cm2 Au surfaces• < 2 fm/s2/Hz1/2 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

18

Experimental investigation of electrostatic dissipationThermodynamic force noise source for LISA and experimental gravitation

n vVdCF

CTkv B

4n vn

V

Stochastic surface potential fluctuations from surface dissipation mixes with static potential differences to give force noise

0 0.2 0.4 0.6 0.8 1 1.2 1.40

0.5

1

1.5

2

2.5

3

3.5

capacitance (pF)

freq

-ind

ES *

107

1N/2S

slope = 2.44(0.03)e-7 /pFchi2 = 1.1 (2 DOF)

0 500 1000 1500-0.6

-0.4

-0.2

0

0.2

0.4

0.6

time (s)

co

ntrib

utio

n to

rque

(fN

m)

averaged residual torque (1N/2S electrodes,from 200 modulation cyc)

averaged torqueafter LPFilter (fcut=10mHz)VMOD (f=1.25mHz,amp=8V)theroretical Prediction (

ES=3.48e-7)

TMOD

• 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 frequencyPadova, 09/07/2012

19

Angular interferometer: nrad/Hz1/2 sensing for sub-fN force detectionBench-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

1 234

3421 “Rotation cancelling” phase combination

Preliminary in-air noise measurements

Padova, 09/07/2012

20Padova, 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

3.5×10-5N*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