Latest developments in LISA PathFinder and the … · LISA PathFinder and the Munich Test Alberto...

IGWM-2, 15-Feb-2012 A. Lobo, LPF and the OSTT 1

Latest developments inLatest developments inLISA PathFinder and theLISA PathFinder and the

Munich TestMunich Test

Alberto LoboICE (CSIC) & IEEC


Plan of talk

1. LISA PathFinder and the LTP2. The Diagnostics subsystem and the DMU

a. Magnetic diagnosticsb. Radiation Monitorc. Thermal diagnosticsd. The DMU, payload computer

3. The OSTT in Munich, Oct-Nov 2011:a. The TOQMb. Test Pland. DI heaters runs

4. Conclusion


1. One LISA arm is squeezed to 30 centimetres:

2. Relax sensitivity by one order of magnitude, also in band:

30 cm

LTP Objectives :

• Drag-free• Interferometry• Phasemeter• Diagnostics• Telemetry• Data processing

LPF basic concept

S Δaω ≤ 3×10−14[1 ω/2π3 mHz

2

] m s−2 Hz−1 /2 , 1 mHz ≤ ω/2π ≤ 30 mHz


LTPLTP


Parts of the DDS(Data and Diagnostics Subsystem)

Diagnostics items:

• Purpose:– Noise split up

• Sensors for:– Temperature– Magnetic fields– Charged particles

• Calibration:– Heaters– Induction coils


Problem: to assess the contribution of a given perturbation to

the total noise, f.Approach: 1) Apply controlled perturbation α to the system

2) Measure “feed-through” coefficient between force and perturbation:

3) Measure actual α with suitable sensors

4) Estimate contribution of α by linear interpolation:

5) Subtract out from total detected noise:

6) Iterate process for all identified perturbations

Noise reduction philosophy

F =∂ f∂

f lin = F

f reduced = f − f lin


Temperature and temperature gradients:– Sensors: thermometers at suitable locations– Control: heaters at suitable locations

Magnetic fields and magnetic field gradients:– Sensors: magnetometers at suitable locations– Control: induction coils at suitable locations

Charged particle showers (mostly protons):– Sensors: Radiation Monitor– Control: N/A

Various diagnostics items


Magnetic sensors

4 tri-axial fluxgates Somewhat distant from TMs


Magnetic field in LTP

Basically caused by spacecraft sources Profile has a clear trough between TMs Linear interpolation is strongly biased (up to 1000%)


Neural network interpolation

12 B-readoutchannels

16 B + ∂B valuesat TM locations

Much improved performance: 5-10% Reliable net training is an issue


Thinking of future GW missions

LTP fluxgate magnetometers have excellent sensitivity, but: They are large → poor space resolution Only a few can be installed They are far from TMs Field and gradient interpolation have unreliabilities

Alternatives are currently investigated at IEEC, e.g. AMRs: They are small → increased significantly space resolution Many can be installed, and closer to TMs Possible back-action sets limits to proximity –under study Detailed field reconstruction accessible Sensitivity is already better than fluxgate's, and improving


Calibration coils

Induction coils cangenerate controlledmagnetic fields.

Analysis of TM responsepermits to estimatesusceptibility andremnant magneticmoments of TMs

Magnetic noise can thenbe precisely quantified


The LPF Radiation Monitor

EQM Radiation Monitor

RM concept

RM shield


– The LPF RM lies outside the LTP, hence is not shielded against incoming particles.

– It is based on a two PIN diodes in telescopic configuration.

– In order for it to be sensitive only to E > 70 MeV, the PINs are placed in the interior of a copper cube, some 6 mm thick, which will prevent particles with energies below that threshold from hitting the detector devices:

The LPF Radiation Monitor


The LPF Radiation Monitor: PSI 2010

RM

Beamcollimator

Beam line


The LTP thermal diagnostics items

– 24 high precision temperature sensors (NTCs)

– 14 precision heaters for noise calibration (NTC + kapton)


The LTP thermal diagnostics items


Precision thermometers

LTP temperature sensors


Precision heaters

– Heat effects are usually difficult to model/study in complex systems like the LTP: Radiation pressure Radiometer effect Outgassing Thermo-elastic phenomena Opto-elastic (induced e.g. from previous) ...

– Analytic approach is thus impracticable in essentially all cases of interest

– Numerical modelling (ESATAN and more) is necessary

– A (copyrighted) model of the LTP exists, which can be (and is) used to define and quantify heater activation schemes

– That allows for a calibration procedure of the sensors as regards the effect of temperature fluctuations on the LTP performance

– Like all models, though, these have to be validated by experiment


Precision heaters

* There are three sets of precision heaters in the LTP

* Total number is 14

* Signals are injected from DMU, normally periodic (square) pulses in the LTP MBW

Placement Type Resistance Peak power Comments

EH walls NTCVariable,2 kΩ at 298K

45 mWPairs of NTCs form single “logical” heaters

OW flanges Kapton 45 Ω 1 W --

Suspension srtuts Kapton 44 Ω 2 W

Only 6 out of 8 struts have a heater

FG

2005


Precision heaters

* There are three sets of precision heaters in the LTP

* Total number is 14

* Signals are injected from DMU, normally periodic (square) pulses in the LTP MBW

Placement Type Resistance Peak power Comments

EH walls NTCVariable,2 kΩ at 298K

45 mWPairs of NTCs form single “logical” heaters

OW flanges Kapton 45 Ω 1 W --

Suspension srtuts Kapton 44 Ω 2 W

Only 6 out of 8 struts have a heater

FG

2005

OSTT


The DMU

• Purpose:– LTP computer

• Hardware:

– Power Distribution Unit (PDU)– Data Acquisition Unit (DAU)– Data Processing Unit (DPU)

• Software:

– Boot SW– Application SW:

Diagnostics items Interfaces: routing to and from OBC

HK acquisition and monitor PM acquisition and processing (DFACS) Laser loop controls

Fully redundant

Fully redundant

Parts of the DDS(Data and diagnostics subsystem)


DMU interfaces


DMU chassis


PDU (nominal)


DPU (nominal)

MIL-STD-1553 Bus(OBC & LTP)

CPU (ERC-32)

EEPROM

CPU (ERC-32)

FPGAPROM

RAM


DAU (nominal)


DMU (finished)


The Munich On Station Thermal Test (OSTT)3 Oct 2011 – 17 Nov 2011

IGWM-2, 15-Feb-2012 A. Lobo, LPF and the OSTT 34Harness

DTA

TOQM


Flight representative parts: OMS: RLU, LMU, LCU, OBI ULU IS FEE DMU RM & Magnetometers Suspension Struts (SS) DI SS heaters DI TS at SS and OB

Non-Flight representative parts: TM dummies No OWs No CM No ISH2 harness OBI wrapped in Al foil Rest of DI TS, placed elsewhere

TOQM summary


OSTT at IABG, Munich Oct-Nov 2011


OSTT test plan


OSTT at IABG, DI cyclings, TP-14


OSTT at IABG, single ST heaters


Conclusions

– DIs are an essential part of the LTP. Nominally, they work OK

– DMU is working very well, ASW 3.4 is stable

– OSTT has shown that: OMS works largely better than requirement Thermal stability is also fully compliant Diagnostics thermal cyclings produce expected response levels Test report is due mid March-2012

– Raw test data will be made available to IEEC for detailed analysis

– LPF is in good state several months ahead of launch


End of presentationEnd of presentation

Latest developments in LISA PathFinder and the … · LISA PathFinder and the Munich Test Alberto...

Documents

Transcript of Latest developments in LISA PathFinder and the … · LISA PathFinder and the Munich Test Alberto...