26-29 March, 2007 Arena Workshop, Tenerife 1

SIAMOIS Sismomètre Interférentiel A Mesurer les Oscillations des Intérieurs Stellaires

Seismic Interferometer to Measure Oscillations in the Interior of Stars

Tristan Buey, Benoît Mosser, Claude Catala, Pernelle Bernardi, Jean-Christophe Leclech, Alain Piacentino, Thierry Appourchaux, Jean-Pierre Maillard, François-Xavier Schmider, Jean-Baptiste Daban, François Fressin, Frédéric Thévenin, Stéphane Charpinet, Michel Dupieux, Denis Fappani, Philippe Mathias et al.

 Observatoire de Paris/LESIA, IAS, UNSA/LUAN, OMP/LATT, IAP, OCA

26-29 March, 2007 Arena Workshop, Tenerife 2

Asteroseismology

Two methods: photometry = space-based observations spectrometry = ground-based observations

Advantages of Doppler measurements:- complementary observations • Bright stars• Low mass starsreduced granulation noise, modes l=3

Scientific requirements: continuous observations & long duration

26-29 March, 2007 Arena Workshop, Tenerife 3

SIAMOIS at Dome C

Observing conditions Consequences

Seeing Fibre = 5" on the sky

No big telescope available at Dome C

Science with a 40-cm telescope

Only circumpolar targets Enough interesting bright targets for more than 6 winters

Duty cycle ~ 90% ! Scientific specification #1 : duty cycle > 85%

Polar night = 3 months Scientific specification #2 : 100-day long run on the same target

Demanding siteProject ~ spatial organizationQuasi-automatic, simple setupReduced mass, power, telemetry

26-29 March, 2007 Arena Workshop, Tenerife 4

InstrumentInstrument

Thermo-mechanical structure.

Optical bench.

Interferometer

Camera

Dedicated Telescope

Bonnette

Calibration

Optical fibers : signal and calibration

Command/control system: Acquisition,image processing …

Vacuum pump

26-29 March, 2007 Arena Workshop, Tenerife 5

Overall description • Divided in four sub-systems :

– a dedicated Telescope with its Bonnette (telescope guiding and fiber coupling).

– an Interferometer and a CCD Camera.

– a structure for thermal and mechanical control.

– a command/control software system (CCS).

• Divided among five laboratories :

– GIGT / OMP (Observatoire Midi-Pyrénées): Bonnette

– LUAN / OCA (Observatoire Côte d’Azur): Telescope

– IAS (Institut d’Astrophysique Spatiale): Thermal structure

– LESIA / OPM (Observatoire Paris-Meudon): Interferometer

– CSIC from Institutode Astrofisica de

Andalusia (in discussion). CCS

• One associated private contractor :

– SESO (Société Européenne de Systèmes Optiques). Optics

26-29 March, 2007 Arena Workshop, Tenerife 6

Instrument

• 40-cm telescope low cost, dedicated to the project • Interferometer monolithic instrument

no moving parts, reduced sizefiber fed

• Post-dispersion efficiency, photon noise limited performances, wide spectral range from 400 to 560nm.

Optical Fiber

For more technical details have a look at the poster.

26-29 March, 2007 Arena Workshop, Tenerife 7

PlanningPlanning

• 2006- design- Achievement of the feasibility phase.

• 2007- thermo-mechanical analysis - Qualification tests.

• 2008- PDR- FDR

• 2009- integration

• 2010- tests- summer campaign: Dome C

• 2011

- first winter at Dome CCost : 860 k€Including ANR : 460 k€

For phase A in 2006(ACI + CSA + PNPS) : 116 k€

26-29 March, 2007 Arena Workshop, Tenerife 8

The constraints

Of development:• Small budget and short planning…• Observation requirements : 90% of duty cycle.

Of the site:• Very difficult to fix anything at Dome C • Wintering assumes a minimum maintenance.• Rather hard environmental conditions; large temperature range, • long travel to the site; shocks and vibrations.

Design:• Highly reliable instrument with easy set up and maintenance.• Qualification like a space instrument for the critical components• Commercial approach for the delivery • Minimal customization and technological developments.• Fully automated instrument for the main (and very simple) mode of observation. • Spares to replace the malfunctioning elements.

26-29 March, 2007 Arena Workshop, Tenerife 9

Response to the Dome-C constraints

Qualification :• Telescope and bonnette outside --> Fully qualified (-100°C/+25°C).• Mechanical bench, thermal control --> No need to be qualified.• Optical components --> Light qualification(-30°C/+25°C), care during transportation, inside a heated shelter.

Simplification :• The instrument is completely tested and set up before arriving in Dome-C. Only standard mechanical integration and simple good health tests are needed.• Apart from calibration modes at the beginning of the observation, only one observation mode, requiring no human intervention (or by remote control).• Apart from the active tracking control loop, no complex control inside the instrument, no critical moving parts (simple shutter).

Specific optical fiber connector to be qualified (soon) at -100°C.

26-29 March, 2007 Arena Workshop, Tenerife 10

Response to the Dome-C constraints

Automation:• Pointing and tracking star: Telescope may point a region of the sky, the bonnette uses a guiding CCD to track the target (control loop).• The telescope makes a U-turn every 24 hours to follow the movement of the Earth (specific mechanism allows the rolling-up of the cables). • Frame Acquisition: the spectra are automatically acquired by the control/command system with all the house-keeping of the instrument.• The thermal control is based on a simple heating system and passive filtering and is naturally automatic.• The mechanical control is based on active autonomous suspension. • The data during the main observation mode are processed via a constant pipeline for: visualization (remote control), data sending to Europe, storage.

26-29 March, 2007 Arena Workshop, Tenerife 11

The Command/Control System

Guiding systemThermal control

systemCamera and HK

Commande/controlsystem

HK

HK : T,PWMCommand : T, PWM

ImageHK (T, P)Exposure, windowing

Raw storageBackup

Pre-processingIHM

Quick-LookData sending

First estimation around 200ko/day

26-29 March, 2007 Arena Workshop, Tenerife 12

• Dome C: a unique site for Asteroseismology3-month of continuous observation with duty cycle ~ 90%

• A specific scientific program after• High performances possible with a 40-cm collector

– Pioneering project at Dome C– FT seismometer: suitable concept for installation and setup at Dome C– Multiplex advantage of FT spectrometry– Small instrument : < 300kg, < 2m3, < 1kW, …– Fairly fast development with a demonstrated feasibility.– Fully automated for the main observational mode.

Conclusion

‘‘Big science’’  at Dome C with a budget < 1 M€, with little maintenance and limited human intervention.