Fringe Detection Methods for Very Long Baseline Arrays (original) (raw)

ADS

;

• Doeleman, Sheperd S. ;
• Moran, James M.

Abstract

In VLBI observations, atmospheric turbulence and local oscillator phase noise often limit the coherence time to a few seconds. When such coherence losses severely limit the integration time, detection thresholds rise and weak sources cannot be detected. We show here that under these conditions, the detection methods and measurements of visibility amplitude and phase can be reformulated in terms of incoherently averaged quantities. The theory is presented by examining the properties of averaged amplitudes and triple products. This paper reviews current detection methods, discusses new techniques, presents applications to recent 3 mm VLBI experiments, and shows that signal processing can significantly improve the probability of signal detection.

Publication:

The Astronomical Journal

Pub Date:

March 1995

DOI:

10.1086/117371

Bibcode:

1995AJ....109.1391R

Keywords:

• Correlation Detection;
• Millimeter Waves;
• Radio Astronomy;
• Signal Detection;
• Signal Processing;
• Signal To Noise Ratios;
• Very Long Base Interferometry;
• Amplitudes;
• Analysis (Mathematics);
• Coherence Coefficient;
• Probability Distribution Functions;
• Sensitivity;
• Astronomy;
• TECHNIQUES: INTERFEROMETRIC