In building long baseline interferometers with many fold mirrors, the wavefront quality, reflectivity loss, and relative dispersion are not the only issues a designer must contend with. The polarization effects from fold mirrors on light can significantly reduce fringe visibility. However, recognizing a mirror’s polarization effects early can influence interferometer design and minimize fold mirrors polarization effects on fringe visibility. In this article, the polarization effects of various mirrors are provided in a simplified manner providing the optical designer with insight into the ill effects mirrors have on a polarization state. Several possible techniques are described to remedy the polarimetric fringe visibility loss. This understanding can provide designers with the necessary tools to minimize polarization visibility loss for a long baseline interferometer.
Georgia State University's Center for High Angular Resolution Astronomy (CHARA) operates a multi-telescope, long-baseline, optical/infrared interferometric array on Mt. Wilson, California. We present an update on the status of this facility along with a sample of preliminary results from current scientific programs.
Georgia State University's Center for High Angular Resolution Astronomy (CHARA) operates a multi-telescope, long-baseline, optical/infrared interferometric array on Mt. Wilson, California. Since its inception, one of the primary scientific goals for the CHARA Array has been the resolution of spectroscopic binary stars, which offer tremendous potential for the determination of fundamental parameters for stars (masses, luminosities, radii and effective temperatures). A new bibliographic catalog of spectroscopic binary orbits, including a calculated estimate of the anticipated angular separation of the components, has been produced as an input catalog in planning observations with the Array. We briefly describe that catalog, which will be made available to the community on the Internet, prior to discussing observations obtained with our 330-m baseline during the fall of 2001 of the double-lined spectroscopic systems β Aur and β Tri. We also describe the initial results of an inspection of the extrasolar planetary system υ And.
Atmospheric fluctuations cause a jitter in the fringe position of ground-based stellar interferometers. To efficiently use the few photons available, an active fringe tracking system is necessary to stabilize the fringe position. This paper briefly describes the different methods of fringe tracking being implemented at the CHARA array, as well as the fringe tracking systems themselves.