Global Effects on Dynamics

Transcription

1 Global Effects on Dynamics Daniel HESTROFFER (IMCCE, Paris) CU4 SSO

2 Outline Asteroids and others population Simulations Global Effects on Dynamics Ground-based compl ementary data 2

3 Asteroids population Detection: almost any object that is brighter than mag V 20 smaller than Φ < 0 7 motion less than 150mas/s Different objects observed NEOs ( 1500), MBAs ( 250,000), Trojans, Centaurs (few 100), TNOs (e.g. Pluto) comets (LPC, JFC), satellites (Ma, J, S, U, N 50) 3

4 Simulations Rendez-vous (F. Mignard) sequence of observations and ephemerides GIBIS CCD proc. (C. Babusiaux, F. Arenou, A. Dell Oro) focal plane and astrometry Input objects for Initial Conditions (IC) NEOs 2 populations known NEAs (90% complete Φ>1km) synthetic population (Bottke et al. 2002) other : astorb.dat (close to completion at V=20) known comets 4

5 Detection size Simulations binaries 5

6 Astrometry Simulations CCD in space global astrometry astrometry at sub-mas level (conservative for NEOs) homogeneous ref frame ; absolute position One instrument size, shape model, spin = parameters for corrections or dynamical model Scanning law not equal for all objects MBAs vs. NEOs & TNOs 6

7 Astrometry 63 obs Simulations A typical MBA, orbital period 5 years Different for NEA, Centaur, or faint object Precision σal(λ) 0.3-5mas (on a transit basis) 7

8 Dynamical model Direct computation Dynamics planets, GR simpl ified, non gravitational simpl ified A i asteroids mutual perturbations pre-selection of close encounters Inversion only Gaia data, only linear case variational equations for partial derivatives iterations for linearisation and goodness of fit Variance Analysis 8

9 Inversion Dynamics Adjustement local (state vector), global parameters Mass close encounters ; binaries Non-gravitational effects comets ; NEOs Global dynamical parameters test of GR (dg/dt, PPN β) global rotation (W o + dw/dt) 9

10 State vector Dynamics Linear Least-Squares: O-C = A.dx = [ λ/ x].dx no long period effects (planetary satellites) cases of rank deficiency - no full osculating elements 10

11 Masses Mouret et al. (2007) J. Hilton Dynamics Close encounters impulse for pre-selection global parameters for inversion 150 masses better than50% 11

12 Local test of GR large # of test particles through solar system Dynamics separate PPN β (a.(1-e 2 )) -1 solar J 2 (a.(1-e 2 )) -2 σ(β) 10-4 σ(j 2 ) 5x10-8 Mercury as sensitive as Mercury Phaethon Icarus 12

13 Ground-based Support P. Tanga N asteroids 13

14 Ground-based Support Ground based Observation during mission for critical objects Observations outside mission mass, GR, non gravitational parameters similar precision ; secular terms direct (astrometry) or indirect (physical parameters for dynamical model) 14

15 Ground based Gaia (DPAC) MBAs mass NEOs + all GR comets + NEOs binaries all post-gaia MBAs NEOs comets NEOs A i mass W, dg/dt mass GR A i satellites orbits, planets Trojans GR TNOs κ 15

16 Discussion End (% Instrument degradation / extended mission Indirect astrometry from (re)reduction with Gaia stellar catalogue Satellites and other long-term effects Planets pseudo-positions Larger system Gaia+GB data Other orbit propagators Dynamical families... 16

17 End (% so, was angular momentum conserved?.. 17

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20 Gaia (350,000 obj.) Ωx-y-z [μas] Results dω/dt [μas/yr] Ġ/G [yr -1 ] κ [m/s 2 ] E-12 [ 8E-11 ] LLR (Williams et al. 2004) E-13 Ephemerides (Folkner et al. 2009) 40 5 E-13 TNOs (Wallin et al. 2007) 2E-10 J 2 alone β alone J 2 global β global correl. Gaia 5E-08 1E-04 5E-08 1E to 0.9 INPOP (Fienga et al. 2008) 2 E-4 LLR - EMP (Williams 04, Pitjeva 05) 1 E-4 Bepi Colombo (Milani et al. 2009) 2 E-9 2 E NEOs (Margot et al. 2009) 20

21 Questions / Réponses q q q r r r 21 D. Hestroffer (IMCCE) CNAP 2011