Narrow Angle Astrometry

Benjamin Lane (California Institute of Technology)

Abstract:

A ground-based long-baseline interferometer offers the potential for very high astrometric precision over ~30-60 arcsecond fields, allowing one to study a range of interesting astronomical phenomena. Particularly exiting examples include micro-lensing events and planets. The high precision comes from the fact that the atmospheric error over such small fields is correlated and can be removed by a differential measurement; depending on atmospheric condition Kolmogorov-based turbulence models predict performance in the 10-100 micro-arcsecond regime for a typical 100-m baseline interferometer operating in the near-IR. Experiments at the Mark III and PTI have achieved the upper range of these predictions and verified the atmospheric models.

In practice, high-precion interferometric astrometry requires careful attention to instrumental design and operation; I will discuss what has been learned at PTI and what should be considered in future experiments.

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Suggested Reading:

• Potential of long-baseline infrared interferometry for narrow-angle astrometry
  M. Shao and M.M. Colavita
  Astron. Astrophys. 262, 353-358 (1992).

• The Palomar Testbed Interferometer
  M.M. Colavita, et al.
  Astrophys. J. 510, 505-521 (1999).

• Measurement of the Atmospheric Limit to Narrow Angle Interferometric Astrometry Using the Mark-III Stellar Interferometer
  M.M. Colavita
  Astron. Astrophys. 283, 1027 (1994).

• Resolving gravitational microlensing events with long-baseline optical interferometry: Prospects for the ESO Very Large Telescope Interferometer
  F. Delplancke, K.M. Górski, and A. Richichi
  Astron. Astrophys. 375, 701-710 (2001).