Meteor astrometry: what accuracy do we need?

Talk presented at the European Space Agency's 2010 Meteor Orbit Determination workshop.

Transcript

1. Meteor astrometry What accuracy do we need? Geert Barentsen - Armagh Observatory - gba@arm.ac.uk MOD 2010
2. ~ 90x50 deg Watec cameras Used to study meteors (PI: Tolis Christou) ~ 3x3 degrees (85mm f1.4) Starlight Xpress HXV-16 CCD (30s + 3s readout) Used to study long-term stellar variability 1 pixel = ~0.001 deg = ~3 meter 1 pixel = ~0.1 deg = ~300 meter The roof of Armagh Observatory ...
3. 22 November 2009, 00h57 UT It's the same meteor !
5. → What accuracy do we need, to make a similar graph for meteoroid streams? 3:2 resonance 7:4 resonance
6. Perseids 2007 (ESA/RSSD Campaign) Large range in semi-major axis ... Poynting-Robertson or just errors?! 109P Jupiter
7. 15 AU 41.4 km/s 10 AU 41.0 km/s 5 AU 39.9 km/s Semi-major axis Speed at 1 AU Sun Semi-major axis is very sensitive to the velocity
8. (R 1 ,T 1 ) (R 18 ,T 18 ) (R 2 ,T 2 ) (R 3 ,T 3 ) (...) ➔ |v| = (R 18 -R 1 ) / (T 18 -T 1 ) = 59.3 km/s ➔ |v| = (R 16 -R 3 ) / (T 16 -T 3 ) = 58.7 km/s ➔ |v| = (R 13 -R 6 ) / (T 13 -T 6 ) = 61.2 km/s ➔ |v| = avg (R a -R b ) / (T a -T b ) = 59.4 km/s Velocity is very sensitive to errors ! R: Position vector T: Time
9. Fakeor simulations • Fakeor = Fake meteor • Input • Radiant (ra, dec, velocity) • Time + entry point • Output • Position of two observing stations with 100km baseline – Meteor at same distance from each station – Optimized convergence angle • Synthetic astrometry from these stations
10. Uncertainty propagation Repeat 1000x (Monte Carlo) x x x x x x SPICE Astrometric error 1/a error We use the synthetic astrometry to recompute the (known) orbit Idea: quantify sensitivity of the semi-major axis by progressively adding errors to the synthetic astrometry.
11. Empirical result: O(error 1/a) ≥ O(error astrometry) − 5 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-3 10-2 10-1 100 101 102 103 Error astrometry (arcseconds) Error in 1/a (AU-1 ) Result: error of 1/a in function of astrometry error (condition: optimal convergence angle)
12. Semi-major axis (a) What accuracy do we really need? This is what the Taurids might look like according to David Asher .... Taurids 7:2 resonance cf. Jeremie's presentation: we need ~0.1-0.01 uncertainty in semi-major axis
13. Observed distribution of Taurids semi-major axis in the IAU database ...
14. sigma(1/a) = 0.01 => Need astrometry better than ~10 arcminutes We add errors to the Taurids model to show the effect of poor orbits: IAU?
15. O(error radiant) ≥ O(error astrometry) What about radiants ? Error of radiant position in function of astrometry error
16. 4-rev 9-rev Leonids 2001 model (McNaught & Asher) What accuracy do we need to separate the radiants of 2 Leonid trails ?
17. Need astrometry better than ~1 arcminute to separate trails. Increasing the number of meteors may not help in the case of large errors ... We add errors to the theoretical radiant distribution:
18. ~3 degree 1 pixel = ~0.001 deg = ~3 meter ~90 degree 1 pixel = ~0.1 deg Shower identification Trail identification
19. Conclusions • At least arcminute-level accuracy is required to uncover the substructure of a meteoroid stream – In the case of optimized geometry – In the case of error-free centroiding – Not necessary to identify showers (e.g., great results from Sirko and SonotaCo) • Further work: build a database of “synthetic meteor observations” to validate algorithms. – Allows to test trajectory algorithms and data quality parameters – May be used to create synthetic videos to test photometry and astrometry algorithms