Introduction
The Haystack Observatory Post-processing System (HOPS) is a software package used for the manipulation of data generated by Very-long-baseline interferometry (VLBI) correlators. It is written in a combination of C/C++ and python. As data pipeline software it sits between the correlator and downstream image-processing and/or geodetic analysis packages. It’s primary purposes are basic fringe-fitting, data calibration/editing/flagging, and problem diagnosis, along with other correlator support and visualization functions. This repository contains software from both the legacy HOPS3 package as well as the currently in-development HOPS4 package. The user can optionally compile the HOPS3 software if they have the additional required dependencies.