Robust determination of optical path difference: fringe tracking at the infrared optical telescope array...

Area of Science:

• Astronomy and Astrophysics
• Optical Interferometry

Background:

• Optical interferometers combine light from multiple telescopes to achieve high angular resolution.
• Accurate measurement of closure phases is crucial for synthesizing high-resolution images in optical interferometry.
• Equalizing optical path lengths is essential for obtaining reliable interferometric data.

Purpose of the Study:

• To introduce and evaluate a novel fringe-packet tracking system for the Infrared Optical Telescope Array (IOTA) interferometer.
• To enhance the accuracy of closure-phase measurements by equalizing optical path lengths.

Main Methods:

• Development of a fringe-packet tracking system.
• Implementation of an algorithm based on double Fourier interferometry to determine wavelength-dependent fringe phases.
• Utilization of a group-delay tracking algorithm to locate fringe packets.
• Simultaneous fringe acquisition on three baselines.

Main Results:

• The fringe-packet tracker achieved a reduction in closure-phase measurement error by a factor of approximately 3.
• The system successfully tracked fringes with signal-to-noise ratios as low as 1.8.
• The tracker demonstrated capability in observing faint stars, down to magnitude mH = 7.0.

Conclusions:

• The developed fringe-packet tracking system effectively equalizes optical path lengths in optical interferometers.
• This system significantly improves the precision of closure-phase measurements, advancing high-resolution astronomical imaging.
• The tracker's performance with low signal-to-noise ratios and faint targets expands the capabilities of optical interferometry.