The Solar System at ~10 mas perspectives for a Fresnel imager Paolo Tanga Marco Delbò Laboratoire Cassiopée, OCA

Observational challenges Hi-res atmospheric activity & aurorae (UV) on Jupiter, Saturn Hi-res atmospheric activity & aurorae (UV) on Jupiter, Saturn Atmospheric activity on the remote planets Atmospheric activity on the remote planets Evolution of fine structures in Saturn’s rings Evolution of fine structures in Saturn’s rings … Trans-Neptunian Object population: Trans-Neptunian Object population: Inventory Inventory Size (albedo) Size (albedo) Anomalous orbits Anomalous orbits Asteroids: Asteroids: Inventory at small sizes Inventory at small sizes Internal structure (mass, size, shape) Internal structure (mass, size, shape) Cometary activity Cometary activity Comets Comets Evolution of chemicals after sublimation Evolution of chemicals after sublimation

Giant planets UV features: UV features: Aurorae Aurorae Upper atmospheric features ( mb) Upper atmospheric features ( mb) Interest Interest Connection to magnetosphere Connection to magnetosphere Coupling to other wavelengths Coupling to other wavelengths Our nearby prototype of extrasolar planets! Our nearby prototype of extrasolar planets! HST, H2 emission (160 nm)

The importance of asteroids… The great issues:  Origin: collisional life, related physics  Dynamical processes: transport, mixing in the primitive nebula, origin of meteorites  Impact risks and mitigation strategy The problem… Very limited knowledge of basic properties: density, porosity… Spectral types and connection to composition Shapes, satellites Size distribution

Itokawa as seen by Hayabusa Is this a cohesionless « gravitational aggregate »? 540 m

How much is/will be known Propertytodayafter Gaia Propertytodayafter Gaia shapes, poles100~100,000 rotation periods100010,000 satellites~ 20 (MBA)? New constraints! surface properties ~ 1000~200,000 astrometry~ 0"50"005 masses,  < 50%~ size / albedos ~

Angular size as a function of distance for objects of 10 and 100 km. The two « p » curves represent the limit size at V=20 (at opposition) for two extreme albedo values. Jupiter Neptune Mars Ceres ~200 asteroids 1 x 10 6 (?)

Areas open to a Fresnel imager Size inventory/improvement km Size inventory/improvement km Macroscopic shapes km Macroscopic shapes km Cometary activity (OH at 308 nm) Cometary activity (OH at 308 nm) Binary asteroids Binary asteroids Discovery Discovery Orbits Orbits

Binary asteroids Importance: Importance: Linked to the collisional physics  past history of the belt Linked to the collisional physics  past history of the belt Period + separation  mass Period + separation  mass If size is known  density (internal properties) If size is known  density (internal properties) Properties: Properties: Wide range of separations Wide range of separations and size ratios! 16% of objects at D<30 km? 16% of objects at D<30 km?

Binary asteroids – the Fresnel imager domain radar/ lightcurves Imaging (AO)

How many asteroids at V=20 ? Evolution of the number of entries H < H lim Evolution of the number of entries H < H lim old files retrieved by D. Hestroffer in the IMCCE archives old files retrieved by D. Hestroffer in the IMCCE archives

45° Geometric observability of orbits L2 Sun

Velocity distribution simulation on 5,000 objects simulation on 5,000 objects main-belt, NEOs main-belt, NEOs  Possible problems related to motion  ~ 12 mas/s

Possible strategies: Priority given to Solar System objects Priority given to Solar System objects Exceptional events (comets, storms on the main planets…) Exceptional events (comets, storms on the main planets…) Specific long-term monitoring programs Specific long-term monitoring programs « Opportunity » targets « Opportunity » targets ~50 asteroids V<20 in 1 sq. degree ~50 asteroids V<20 in 1 sq. degree Few requirements on pointing Few requirements on pointing

Conclusions Asteroids offer a wide variety of targets Asteroids offer a wide variety of targets Binary objects Binary objects Cometary activity Cometary activity Giant planets Giant planets Interesting features at all wavelengths Interesting features at all wavelengths Can help in modeling extrasolar planet observations Can help in modeling extrasolar planet observations

Configuration space period-diameter Configuration space period-diameter no very fast rotator due to centrifugal force no very fast rotator due to centrifugal force lack of global cohesion lack of global cohesion

The occultation revival Today Today poor predictability for objects <50 km poor predictability for objects <50 km bright Hipparcos/Tycho stars favoured bright Hipparcos/Tycho stars favoured ~0.1 events/objects/year ~0.1 events/objects/year Current practical limit: 100 km at 10% accuracy Current practical limit: 100 km at 10% accuracy After Gaia (100 X orbit improvement): After Gaia (100 X orbit improvement): Uncertainty smaller than the asteroid at >20 km Uncertainty smaller than the asteroid at >20 km 1-m automated telescope(s): 1-m automated telescope(s): Single site: events/yr for an object Single site: events/yr for an object of ~20 km of ~20 km Network: completeness of diameters Network: completeness of diameters > 20 km in a few yr > 20 km in a few yr Projected shape known Projected shape known

Light curves Asteroid’s magnitude function of: Asteroid’s magnitude function of: shape, rotation period, direction of spin axis shape, rotation period, direction of spin axis Direct problem: Direct problem: model of light curves for different shapes and rotation model of light curves for different shapes and rotation Inverse problem: Inverse problem: find the rotation parameters from photometric data find the rotation parameters from photometric data strongly non linear strongly non linear not well conditioned if period unknown not well conditioned if period unknown Animation: M. Delbo