HELAS, Nice 27 September 2006 Visible light Imager and Magnetograph T.Appourchaux on behalf of the VIM team IAS

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HELAS, Nice 27 September 2006

Visible light Imager and Magnetograph

T.Appourchaux on behalf of the VIM teamIAS






Contents

• Scientific objectives• Instrument design• Instrument challenges• What now ?






Scientific objectives

• Probe the Solar Dynamo:– High-latitude fields, flows and seismic waves

• Explore at all latitudes:– Energetics, dynamics and fine-scale structure of the

Sun’s magnetized atmosphere

• Investigate links:– Between the solar surface, corona and inner heliosphere






Stereoscopic helioseismology






What are the observables?

• High and low resolution imaging• Vector magnetic field• Solar radial velocities






How can we do that?

• High and low resolution imaging– Full Disk Telescope (FDT), Field of view >2.5 deg, 2.5 cm dia.– High Resolution Telescope (HRT), 150 km resolution at 0.22 AU (1”), Field of view >15, 16 cm dia;

• Vector magnetic field– Stokes polarimetry in FeI 6173 Angström

• Solar radial velocities– 5 to 6 positions on the line profile






VIM: Subsystems• FDT:

– Off-pointing mechanism: wedge prism (2.5 deg)

• HRT:– Image Stabilization System (0.02” overs 10 s)– Filtergraph (passband of 75 mAngström)– Polarization modulation package (PMP based on Liquid

Crystal Variable Retarder)

• Camera: 2k x 2k Active Pixel Sensor• Electronic box






The VIM team• Germany:

– PI ship, management, HRT, Structure:MPS– Pointing: KIS

• Spain:– FDT, PMP: INTA– E-box: IAA– Structural and thermal analysis: IDR

• France:– Filtergraph: IAS






Filtergraph concept• Telecentric

– No velocity change– Passband shifted and widened– All defects imaged on the solar image– Aperture apodization

• Baseline solution: Lithium Niobate Fabry-Pérot, 6 cm dia.

• Back-up: Fabry-Pérot with piezoelectric spacers






Tunability requirement(TN-VIM-2005-02 and 03)






Response (TN-VIM-2005-01)











Challenges

• Space qual. of LCVR

• Space qual. Of LiNb03 etalons

• High solar flux 25 solar constant…

• Reduced telemetry: 20 kbits/s






What now ?

• Call for Letter of Intent (ESA, 11 July 06)

• MPS response as of 15 September 06

• Heat Shield study till end 2007

• AO hopefully in 2008

• Launch in 2017

• Observation till 2023-2028…

Documents

HELAS, Nice 27 September 2006 Visible light Imager and Magnetograph T.Appourchaux on behalf of the VIM team IAS