Free fall test overview

Hanns Selig(ZARM)

F. Liorzou(ONERA)

MICROSCOPE Colloquium II

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CNESS. Leon, M. Bach, A. Robert et al.

ONERAP. Touboul, M. Rodrigues et al.

OCAG. Metris et al.

ZARMC. Lämmerzahl, H. Selig et al.

PTBF. Löffler, D. Hagedorn et al.

MICROSCOPE

Cooperation

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Free Fall

Test and

Verification Payload

Modellingand

Simulation

In‐Orbit Calibration

Data Processing

WPs at ZARM

Work Packages at ZARM for MICROSCOPE

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• Project leader: Claus Lämmerzahl

• Project members: - Free fall tests

Hanns SeligMarcus StadtlanderManfred Behrens

- Modelling and mission simulation

Stefanie BremerMeike ListBenny RieversHanns Selig

funded by DLR Agency

MICROSCOPE

The MICROSCOPE-Team at ZARM

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• Standard Capsule / Freeflyer / Catapult

MICROSCOPE

Free fall tests – Drop Tower Facility

Drop Tower facility research areas• Fundamental physics

• Fluid dynamics

• Combustion research

• etc.

7 MICROSCOPE

Carbon‐Freeflyer

Power supply

Computer

AccelerometerONERA

Radio‐modul

Power supply

Computer

Drop capsule

Free‐Flyer

radio‐moduls

Free fall tests - Freeflyer

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Catapult

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Standard* Freeflyer Catapult CatapultFreeflyer

µg-duration

4.7 s 3.5 stoo short

> 9 s 8 snot yet available

µg-quality 10-6 g 10-8 (-7) g 10-6 g 10-8 g (tbc)

* blocked Freeflyer

Comparison of modes

10 MICROSCOPE

Free fall tests QM

11 MICROSCOPE

Free fall tests QM

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ONERA ULTRA SENSITIVE ACCELEROMETERTestability on ground

Their testability on ground requires creating a low gravity environment to verify their functionalities and partially their performances

Ultra sensitive accelerometers are optimised for the in orbit environment

operate within ranges up to 10-6 ms-2

Reach performances of 10-12 ms-2/sqrtHz: heavy test masses

Free fall tests are the only way to obtain such amicrogravity environment that represent space conditions.

Pt/Rh : 1.6kg

Pt/Rh : 0.47kg

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MICROSCOPE SENSOR DEVELOPMENT

•PRE QUALIFICATION TEST=> Several drops in order adjust the parameters to control the Proof

Masses for all axis in the drop tower condition

•REFERENCE DROP

•ENVIRONMENTAL TEST• Vibration test • Thermal vacuum• Shock

•VERIFICATION DROP

•SAME sequence for Flight models

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DROP TEST CONFIGURATION

FEEU:Control voltages boosted to 100V

ICU:Servo Control laws Parameters patchableadjusted for the drop

24 V

Batteries

• A challenge for getting a convergence within 4.7 seconds

• Electrode voltage control boosted from 50V to 100V

• Servo control (PID type) optimized

PXI spyFor data acquisition

• Data acquisitionData, sampled at 1kHz, are acquired by the ICU from the FEEU via one bi-directional RS422 link at 1.25Mbaud. A spy line has been implemented from this link to an acquisition and storage system in order to collect data during the drop.

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Control type implemented for the fall: simulation

DROP SIMULATIONS

• They allow to tune the corrector and optimise it for the test

Position Velocity Acceleration

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Capsule integration: Drop in Y direction

• Optimisation of the capsule balance is a key point in the experiment preparation

=> part of the residualatmospheric drag can betransferred from the fallaxis to axis of thehorizontal plan.

Perturbation minimization• Outside win• Total immobility • Switch off on board

computer fans

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Test result: control of 6x2 degree of freedom of both internal and external mass

X Y

Z

Position and rotation

Accelerations

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Qualification tests: tool for data extension

DROP SIMULATIONS

• They allow to interpret the measured data by extending by calculation, the not yet converged curve to check the trend.

T0 for the simulation Convergence at about 9 seconds

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Conclusion for the free fall test

• Five campaigns, with a total of 50 falls, have been so far conducted in order to provide a better assessment of the dynamical behaviour of the instrument.

• Thanks to this approach, a typical dynamical response, with optimised control laws versus controllers bandwidth and fall duration, has been defined.

• This allows the establishment of qualification and acceptance criteria for the flight models.

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Conclusion for MICROSCOPE mission

The acquisition and control of the 6 degree of freedom of the two cylindrical shape proof masses with significant weight constituting the MICROSCOPE instrument core has been successfully tested for the first time in the BREMEN drop tower.

This success is an important step for MICROSCOPE mission that contributes to the qualification of the instrument by confirming good operations of the twelve electrostatic digital loops in micro gravity and the good reliability and robustness of the configuration.