Science Objectives They are two-fold:  Solar Understand plasma processes: current sheets, reconnection, "blinkers", double layers, Alvenic waves heating, plasmoid formation, electrodynamics coupling Untangle magnetohydrodynamic configurations: coronal loops, prominences, chromospheric spicules, sunspots, photospheric flux tubes Probe radiation hydrodynamics: granulation, acoustic heating, shock formation and dissipation Determine fine scale structure activity: evolution of magnetic patterns, flux emergence and disappearance Discover the mechanisms of eruptive phenomena and instabilities: flares, micro-flares, "disparition brusques" of prominences, surges, coronal bullets, ephemeral active region Planetary Atmosphere of the giant planets: Jupiter (balance between solar and auroral energy), Saturn (auroral UV emission) Magnetospheric activity of Mercury Monitoring UV contrasts and Albedo of Venus atmosphere Contribution to the study of minor bodies (comets, asteroids) by images in FUV and UV (over 3 years, up to 40 asteroids will be seen with a size larger than 75 mas)

Mission Description

• 3-Telescope basic imaging interferometer capable of 0.025 arcsec (20 km on the Sun) spatial resolution in the UV of large 40" field-of-view instantaneously
• Suited for optimized low-cost CNES PROTEUS Platform (1 meter baseline)
• Benefits from a Sun-synchronous low earth orbit

Measurement Strategy

• Fast imaging sequences at very high resolution, near processes scales, of the chromosphere, transition region, corona and photospheric magnetic fields
• Focal instrument (a subtrative double monochromator) allows simultaneous high spectral resolution (0.002 nm) on high resolution images in FUV and UV
• High throughtput of the concentrated fine structure emission allow very time resolution down to ms in flares
• Large collecting primaries (3 telescopes of diameter 35 cm) and perfect alignment (cophased interferometry) allow exposures on planets of the order of 10 minutes with a 2.5 times better spatial resolution than the Space Telescope

Technology Requirements

• Compact and robust reference interferometer development for the phase control
• Innovative real-time control approach
• Optimized data compression thechniques for interferograms recording (wavelets)

Status

• To be proposed in answer to the CNES AO for Intermediate Missions, January 7th, 1998
• Under consideration for ESA F2/F3 Medium Mission
• Adaptable (via the Hexapod Pointing Platform) to the Space Station

Spatial and Spectral Possible Characteristics of SOLARNET Focal Plan Instrumentation

Wavelength	Field-of-view	Detectors		Spatial resolu-	Spectral
range (nm)	(arcsec)	Pixels	Type	tion (arcsec)	resolution (nm)
FUV: 117 - 200 130 - 300	40 x 40 60 x 60	2048 x 2048	ICCD	0.025 - 0.04 0.04 - 0.1	0.002 ~ 20
UV: 280 - 400	60 x 60	2048 x 2048	ICCD	0.06 - 0.08	0.01 (0.001*)

* This could be achieved by an extra filtering (Fabry Perot).

SOLARNET Resources Summary

Mass	160 kg (including 20% margin)
Telemetry	400 kbits/s average (4 Mbits/s at maximum rate)
Envelope	Ø110 x 150 cm3 (3 x Ø35 cm telescopes)
Primary pointing accuracy	± 0.5°
Primary pointing stability	± 0.03°/s
Internal Active pointing stability	< 12 mas
Internal phase control	< l/8 (at Lyman a, 120 nm)
Field-of-view	1.2° (Sun viewing)
Power	60 watts (peak: 75 watts)
Mission duration	2 nominal (and up to 6 years)

More on SOLARNET

• General Schematic Optical Design
• Principle and Implementation of the Focal Instrument, the Double Monochromator
• Imaging Principle and Performances
• Demonstrating the Cophasing with 2 and 3 Telescopes

See also, for more completness, our last paper detailing the program, design, focal instrument, image reconstruction, etc.

Science Team

Luc Damé (Chair) Service d'Aéronomie du CNRS BP 3, F-91371, Verrières-le-Buisson Cedex, France Tel.: [33] 1 64474328 Fax: [33] 1 69202999 e-mail: luc.dame@aerov.jussieu.fr
Michel Hersé Service d'Aéronomie du CNRS BP 3, F-91371, Verrières-le-Buisson Cedex, France Tel.: [33] 1 64474280 Fax: [33] 1 69202999 e-mail: michel.herse@aerov.jussieu.fr	Pierre Cugnon Observatoire Royal de Belgique 3 Avenue Circulaire, B-1180 Bruxelles, Belgique Tel.: [32] 2 3730276 Fax: [32] 2 3730224 e-mai: Pierre.Cugnon@ksb-orb.oma.be
Anny-Chantal Levasseur-Regourd Service d'Aéronomie du CNRS BP 3, F-91371, Verrières-le-Buisson Cedex, France Tel.: [33] 1 64474293 Fax: [33] 1 69202999 e-mail: aclr@aerov.jussieu.fr	André Preumont Dépt. de Génie Mécanique et Robotique Université Libre de Belgique Av. F.D. Roosevelt, B-1050, Bruxelles, Belgique Tel.: [32] 2 6504663 Fax: [32] 2 6504660 e-mai: apreumon@ulb.ac.be
Thomas Widemann Service d'Aéronomie du CNRS BP 3, F-91371, Verrières-le-Buisson Cedex, France Tel.: [33] 1 64474256 Fax: [33] 1 69202999 e-mail: thomas.widemann@aerov.jussieu.fr	Sami K. Solanki Institut Für Astronomie, ETH-Zentrum, CH-8092, Zürich, Switzerland Tel.: 41] 1 6323810 Fax: [41] 1 6321205 e-mail: solanki@astro.phys.ethz.ch
Francesco Angrilli CISAS - Universita di Padova Via Gradenigo 6A, I-35100, Padova, Italy Tel.: [39] 49 8276790 Fax: [39] 49 8276785 e-mail: Angrilli@mail.dim.unipd.it	Philippe Lemaire Institut d'Astrophysique Spatiale Université Paris XI, Bât. 121, F-91405, Orsay Cedex, France Tel.: [33] 1 69858622 Fax: [33] 1 69858675 e-mail: lemaire@iaslab.ias.fr
Gianandrea Bianchini (Instrument Scientist) CISAS - Universita di Padova Via Gradenigo 6A, I-35100, Padova, Italy Tel.: [39] 49 8276808 Fax: [39] 49 8276785 e-mail: mecca01@ipdunivx.unipd.it	Renée Prangé Institut d'Astrophysique Spatiale Université Paris XI, Bât. 121, F-91405, Orsay Cedex, France Tel.: [33] 1 69858581 Fax: [33] 1 69858675 e-mail: Prange@iaslab.ias.fr
Roberto Ragazzoni Osservatorio Astronomico di Padova vicolo dell'Osservatorio, 5 I-35122, Padova, Italy Tel.: [39] 49 8070268 Fax: [39] 49 8293416 e-mail: ragazzoni@astrpd.pd.astro.it	Brigitte Schmieder DASOP, Observatoire de Paris 5 Place Jules Janssen F-92195, Meudon Cedex, France Tel.: [33] 1 45077817 Fax: [33] 1 45077959 e-mail: schmieder@obspm.fr
R Kariyappa Indian Institute of Astrophysics, Koramangala, Bangalore 560034, India Tel.: [91] 80 5530672 Fax: [91] 80 5534043 e-mail: rkari@iiap.ernet.in	Philippe Zarka DESPA, Observatoire de Paris 5 Place Jules Janssen F-92195, Meudon Cedex, France Tel.: [33] 1 45077819 Fax: [33] 1 45072806 e-mail: zarka@obspm.fr