The Solar System at The Solar System at ~10 mas ~10 mas

perspectives for a Fresnel perspectives for a Fresnel

imagerimager Paolo TangaPaolo Tanga

Marco DelbòMarco Delbò

Laboratoire Cassiopée, OCALaboratoire Cassiopée, OCA

Observational challengesObservational challenges Hi-res atmospheric activity & aurorae (UV) on Hi-res atmospheric activity & aurorae (UV) on

Jupiter, SaturnJupiter, Saturn Atmospheric activity on the remote planetsAtmospheric activity on the remote planets Evolution of fine structures in Saturn’s ringsEvolution of fine structures in Saturn’s rings …… Trans-Neptunian Object population:Trans-Neptunian Object population:

InventoryInventory Size (albedo)Size (albedo) Anomalous orbitsAnomalous orbits

Asteroids:Asteroids: Inventory at small sizesInventory at small sizes Internal structure (mass, size, shape)Internal structure (mass, size, shape) Cometary activityCometary activity

CometsComets Evolution of chemicals after sublimationEvolution of chemicals after sublimation

Giant planetsGiant planets UV features:UV features:

AuroraeAurorae Upper atmospheric Upper atmospheric

features (40-100 mb)features (40-100 mb)

InterestInterest Connection to Connection to

magnetospheremagnetosphere Coupling to other Coupling to other

wavelengthswavelengths Our nearby Our nearby

prototype of prototype of extrasolar planets!extrasolar planets!

HST, H2 emission (160 nm)

The importance of The importance of asteroids…asteroids…

The great issues: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…The problem…Very limited knowledge of basic properties: density, porosity… Spectral types and connection to composition Shapes, satellites Size distribution

Itokawa as seen by Itokawa as seen by HayabusaHayabusaIs this a cohesionless « gravitational aggregate »?Is this a cohesionless « gravitational aggregate »?

540 m

How much is/will be knownHow much is/will be known

PropertyProperty todaytoday after Gaiaafter Gaiashapes, poles 100 ~100,000

rotation periods 1000 10,000

satellites ~ 20 (MBA) ? New

constraints!

surface properties ~ 1000 ~200,000

astrometry ~ 0"5 0"005

masses, < 50% ~ 50 150

size / albedos ~2000 3000

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.

Jup

iter

Nep

tun

e

Mar

s

Ceres

~200 asteroids

1 x 106 (?)1 x 106 (?)

Areas open to a Fresnel Areas open to a Fresnel imagerimager

Size inventory/improvement 10-100 Size inventory/improvement 10-100 kmkm

Macroscopic shapes 10-100 kmMacroscopic shapes 10-100 km Cometary activity (OH at 308 nm)Cometary activity (OH at 308 nm)

Binary asteroidsBinary asteroids DiscoveryDiscovery OrbitsOrbits

Binary asteroidsBinary asteroids Importance:Importance:

Linked to the collisional physics Linked to the collisional physics past history of the belt past history of the belt Period + separation Period + separation mass mass If size is known If size is known density (internal properties) density (internal properties)

Properties:Properties: Wide range of separations Wide range of separations

and size ratios!and size ratios! 16% of objects at D<30 km?16% of objects at D<30 km?

Binary asteroids – the Fresnel Binary asteroids – the Fresnel imager domainimager domain

radar/lightcurves Imaging (AO)

How many asteroids at How many asteroids at V=20 ?V=20 ?

Evolution of the number of entries H < HEvolution of the number of entries H < Hlimlim

old files retrieved by D. Hestroffer in the IMCCE archivesold files retrieved by D. Hestroffer in the IMCCE archives

45°

Geometric observability of Geometric observability of orbitsorbits

L2

Sun

Velocity distributionVelocity distribution

simulation on 5,000 objectssimulation on 5,000 objectsmain-belt, NEOsmain-belt, NEOs

Possible problems related Possible problems related to motionto motion

~ 12 mas/s

mas/s

%

-40 -30 -20 -10 0 10 20 30 400

1

2

3

4

5

Possible strategies:Possible strategies:

Priority given to Solar System objectsPriority given to Solar System objects Exceptional events (comets, storms on Exceptional events (comets, storms on

the main planets…)the main planets…) Specific long-term monitoring programsSpecific 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 pointingFew requirements on pointing

ConclusionsConclusions Asteroids offer a wide variety of Asteroids offer a wide variety of

targetstargets Binary objectsBinary objects Cometary activityCometary activity

Giant planetsGiant planets Interesting features at all Interesting features at all

wavelengthswavelengths Can help in modeling extrasolar Can help in modeling extrasolar

planet observationsplanet observations

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

The occultation revivalThe occultation revival TodayToday poor predictability for objects <50 kmpoor predictability for objects <50 km bright Hipparcos/Tycho stars favouredbright Hipparcos/Tycho stars favoured ~0.1 events/objects/year~0.1 events/objects/year Current practical limit: 100 km at 10% Current practical limit: 100 km at 10%

accuracyaccuracy

After Gaia (100 X orbit improvement):After Gaia (100 X orbit improvement): Uncertainty smaller than the asteroid at Uncertainty smaller than the asteroid at

>20 km>20 km 1-m automated telescope(s):1-m automated telescope(s):

Single site: 20-40 events/yr for an object Single site: 20-40 events/yr for an object of ~20 kmof ~20 km Network: completeness of diameters Network: completeness of diameters > 20 km in a few yr> 20 km in a few yr

Projected shape knownProjected shape known

Light curvesLight curves Asteroid’s magnitude function of:Asteroid’s magnitude function of:

shape, rotation period, direction of shape, rotation period, direction of

spin axisspin axis

Direct problem: Direct problem: model of light curves for different model of light curves for different

shapes and rotationshapes and rotation

Inverse problem: Inverse problem: find the rotation parameters from find the rotation parameters from

photometric dataphotometric data

strongly non linearstrongly non linear

not well conditioned if period not well conditioned if period

unknownunknown

Animation: M. Delbo