Geert Barentsen
April 19, 2010
110

# Meteor astrometry: what accuracy do we need?

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

April 19, 2010

## Transcript

1. ### Meteor astrometry What accuracy do we need? Geert Barentsen -

Armagh Observatory - [email protected] 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 ...

4. None
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

...
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?

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