Gaia: an unprecedented observatory for Solar System objects Paolo Tanga Observatoire de la Côte d’Azur (France) P. Tanga – ELSA school 2007 Summary Intro: the Solar System The general picture Most relevant objects for Gaia Asteroids properties, main facts and unknowns Traditional observing techniques Asteroids as seen by Gaia Peculiar issues in SSO observations by Gaia
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Gaia: an unprecedented observatory for Solar System objects
Paolo TangaObservatoire de la Côte d’Azur (France)
P. Tanga – ELSA school 2007
SummaryIntro: the Solar System
The general picture
Most relevant objects for Gaia
Asteroids properties, main facts and unknowns
Traditional observing techniques
Asteroids as seen by Gaia
Peculiar issues in SSO observations by Gaia
P. Tanga – ELSA school 2007100000 AU
P. Tanga – ELSA school 2007
Gaia will mainly observe…Asteroids
Remnants of Solar System formationAltered/shattered by mutual collisionsMain Belt: source of Earth Crossers
CometsPrimitive material from the outer Solar System
Itokawa by the Hayabusa missionIs this a gravitational aggregate?
540 m
P. Tanga – ELSA school 2007
So, why are we interested in asteroids?
To understand their structure and evolution :
To improve Solar System ephemeris:Current accuracy : ~1 km/ 10 yr Earth, Mars (Standish, Fienga 2001)
~100 km / 10 yr for several NEOs
The great unknowns : density, porosity…Gravitational aggregates or solid bodies?The origin of shapesThe collisional historyImpact risks and mitigation strategy
P. Tanga – ELSA school 2007
Gaia, 5 years of sky scans…
P. Tanga – ELSA school 2007
t1
t3
t4t5
t6 t7
t2
P. Tanga – ELSA school 2007
Gaia and the Solar System - observablesAll objects observed, V<20, size <200 mas
~70 observations / object / 5 years
Astrometry and photometry for:3·105 Main Belt & Near Earth AsteroidsComets and TNOsasteroid / planet satellites
Spectroscopic properties (small dispersion)
P. Tanga – ELSA school 2007
What Gaia can do for asteroids?Uncertainties from Earth from Gaia (each obs.)
Astrometry ~0.2-1 asPhotometry ~0.05 magV lim ~23
~0.2-1 mas~ 0.005 ~ 20
Gaia data can be used for:Orbit accuracy improvementDynamical familiesMass determination for largest asteroidsShapes and sizesSatellites of planets and asteroidsRelativity testsDetection of cometary activity…
P. Tanga – ELSA school 2007
Orbit improvement
Accuracy from a pure Gaia data set:102-103 better than current