We present the design and implementation of an automated data calibration and reduction pipeline for very-long-baseline interferometric (VLBI) observations taken at millimeter wavelengths. These short radio-wavelengths provide the best imaging resolution available from ground-based VLBI networks such as the Event Horizon Telescope (EHT) and the Global Millimeter VLBI Array (GMVA), but require specialized processing due to the strong effects from atmospheric opacity and turbulence as well as the heterogeneous nature of existing global arrays. The pipeline builds upon a calibration suite (HOPS) originally designed for precision geodetic VLBI. To support the reduction of data for astronomical observations, we have developed an additional framework for global phase and amplitude calibration which provides output in a standard data format for astronomical imaging and analysis. We test the pipeline on observations taken at 3.5 mm (86 GHz) by the GMVA joined by the phased Atacama Large Millimeter/submillimeter Array in April 2017, and demonstrate the benefits from the specialized processing of high frequency VLBI data with respect to classical analysis techniques.
@article{arxiv.1903.08832,
title = {EHT-HOPS pipeline for millimeter VLBI data reduction},
author = {Lindy Blackburn and Chi-kwan Chan and Geoffrey B. Crew and Vincent L. Fish and Sara Issaoun and Michael D. Johnson and Maciek Wielgus and Kazunori Akiyama and John Barrett and Katherine L. Bouman and Roger Cappallo and Andrew A. Chael and Michael Janssen and Colin J. Lonsdale and Sheperd S. Doeleman},
journal= {arXiv preprint arXiv:1903.08832},
year = {2019}
}