Technical Operations Workshop (TOW) 2023 logo in a blue circle

Everyone who plans to attend the IVS 2023 Technical Operations Workshop (TOW) must register. Registration consists of three parts:

Please contact Heidi Johnson at Haystack if you need assistance.

TOW 2023: Course Descriptions

There are four types of courses to be offered at the Technical Operations Workshop (TOW). All workshop and seminar classes have a time slot of 75 minutes; a 15-minute overlay time follows to be used for final questions and change of class rooms for the subsequent class. Lectures have a time slot of 30 minutes, except for the VLBI Basics lecture, which is 60 minutes long.

  • Operations Workshops are hands-on sessions with a maximum of about 5 participants each. Each member of the class will have an opportunity to participate actively in the training.
  • Maintenance Workshops are presentations to an audience of 10-20 people. The classes will begin with instruction and demonstration, and there may be some hands-on training. A large fraction of the time is allowed for discussion and question/answer periods. The subject matter includes a variety of topics.
  • Seminars are presentations including demonstrations to an audience of 20-60 people, depending on the topic. The subject matter includes a variety of special interest topics.
  • Lectures are intended for a general audience. The subject matter includes topics that we believe are of interest to everyone, or include announcements or information that everyone should be aware of. All attendees at the workshop will be scheduled for the lectures.

Operations Workshops

Operations Workshops are hands-on sessions with a maximum of about 5-7 participants each. Click each class name to view full details, including teacher name(s), experience level, and description.

Teachers: Mike Poirier, Alex Burns

Experience level:
Beginners and advanced levels; new material on the VGOS operation will be

This is a double-length class that will include both pre-checks and operations. This class is offered with two formats. One format is for students with stronger English skills and will move at a faster pace. The other format is for students with weaker English skills, will move at slower pace, and have more pauses for material that may be difficult to understand in translation.

Pre-checks: We will practice all of the procedures and operational tests that should be performed before each experiment to ensure that all of the equipment is set up and working properly, starting with drudging the schedule file and ending with pre-session email to ops. Pointing and gain calibration will be covered in separate workshops. This class is for people who use the PC Field System to control data racks such as the Mark IV, VLBA, DBBC and RDBE. The Mark5B and Mark6 will be discussed at the operational level. The class will use the Westford VGOS system and the Mark IV, with appropriate notes made about differences for other systems. The RDBE and Updown converters will be discussed in detail.

Operations: We will practice experiment operations from starting the schedule to the post-session operational report with hands-on by students during the session. The use of the “logpl” program for plotting data from the log during and after the experiment will be demonstrated along with other tools available found in the PCFS. This class will be held at Westford, using the VGOS RDBE and Mark 6 recorder.

Teachers: Mike Poirier, Alex Burns

Experience level: Advanced level with frequent student interaction.

Description: Loss of data issues compiled from 2014 from all stations will be discussed in detail with proper recovery and simulations. This will be open forum with input and suggestions from all advanced students, many that have experienced these issues. Topics will include: (1) Power failure recovery, starting from scratch. (2) Telescope failure, stuck, poor offsets, slewing. (3) Mark 5 and 6 issues including operational recovery guidelines and power supply repair. (4) Maser signal failures including 5 MHz and 1PPS at the operational level to recover. (5) Data rack failure from Video Converters, Receiver and IF issues, Phase calibration, RDBE and Up-Down converters. Station repair guidelines and proper tools and test equipment for students that may have these skills.

Teachers: Chet Ruszczyk, John Barrett

Experience level: Advanced.

Description: This class will provide further details and explanations of operating Mark 6 systems at stations extending on what is covered in the VLBI Session Pre- checks and IVS Operations class. In addition, details will be given on the usage of Mark 6 systems when attached to a correlator. There are commonalities between the two deployment options; however, there are also operational peculiarities for each option that early users should be aware of.

Teachers: Christian Plötz

Experience level: Beginners.

Description: This workshop will address cryogenic system and receiver maintenance from the operational perspective. The goal is to improve system reliability, reduce downtime, and lower operational cost. Workshop participants will receive helpful hints for recovery from vacuum failures, contaminated helium systems, and the use of standardized maintenance procedures with some common pitfalls identified. General cryogenic “Do’s and Don’ts” will be discussed. This session will not address the theory of cryogenics or the internal workings of a dewar.

Maintenance Workshops

Maintenance workshops are presentations or demonstrations to an audience of 10 or fewer people, with discussion and questions. There may be some hands-on training.

Teachers: Alexander Neidhardt

Experience level: Beginners.

Description: This course describes the general structure of the NASA Field System, including important control files, program locations, handling, and so on. We will take a look into installation and setup. Main part is the use of the FS and the adaption of the PC for the Field System.

Teachers: Michael Lindqvist

Experience level: Beginners; some new material.

Description: This course covers using ONOFF and GNPLT. Instruction will be given on the preparation and execution of ONOFF for the automatic acquisition of amplitude calibration data. Attendees will learn about the necessary procedure files, methods of measuring noise diode temperature and gain curves, and the interpretation of the resulting log files. The course will provide basic instruction on analyzing gain calibration data with GNPLT. Typical tasks (such as calibration of Tcal and gain curves) will be described step-by-step, a general discussion about GNPLT data analysis capabilities will also be held. Some time will be reserved to include the possibility of giving feedback and requesting improvements in the features of the gain calibration tools.

Teachers: Michael Lindqvist, John Swoboda

Experience level: Beginners; some new material.

Description: It is becoming increasingly difficult to protect observations from radio interference as use of the spectrum increases for both terrestrial and space-borne services. This workshop will cover the effects of radio interference on VLBI observations, sources and identification of RFI, and possible mitigation techniques for RFI. Methods for conducting an RFI survey will be reviewed, and initial results from broadband surveys undertaken for the VGOS project at several sites will be summarized.  Information is given about spectrum management and its work with an emphasis on the preparation for the World Radio Conference 2023 (WRC23).

Teachers: Ganesh Rajagopalan

Experience level: Beginners.

Description: The phase calibration system is the primary means for ensuring that instrumental effects in the receiver and VLBI terminal do not corrupt the group delay measurements. This course will cover the basic concepts and hardware implementation of the calibration system, including the Mark IV cable measurement system. The nature and causes of spurious signals, which can degrade the calibration accuracy, will be described. Following the phase cal basics, we will review the fundamentals of measuring a power spectrum with an analog RF or FFT-based spectrum analyzer. Applications to VLBI system testing and troubleshooting will be discussed and demonstrated, with a particular emphasis on phase noise and modulation in LO and phase calibration systems. The detection of spurious phase cal signals with a spectrum analyzer will also be treated, along with the diagnosis and cure of such signals.

Teachers: Ganesh Rajagopalan

Experience level: Beginners.

Description: This course is intended to provide a description of the tests that stations should periodically perform to evaluate the performance of their station. These checks are more advanced than the ones covered in the VLBI Session Pre-checks and IVS Operations course, but most are covered in more detail in other courses. This course works through the list of checks, explains the reasons for the tests, provides some tips on performing them, how to use systests scripts for automating and analyzing measurements, and a chance to ask questions about them. The systests scripts are an important tool for testing and verification for stations that have Mark IV Decoders. In order to have a full grounding in this material it is recommended that anyone signing up for this course should also take some other courses unless they are already familiar with the material in these courses. The recommended other courses are: RFI Sources, Identification, Mitigation and Phase Cal Basics and RF System Testing. Some additional material on troubleshooting not covered in other courses will be presented here. This course will also give an introduction on how VLBI electronics works.

Teachers: Phillip Haftings, Sara Hardin

Experience level: Beginners.

Description: This seminar covers the coordination of observations, the logistics of media distribution, the set-up of correlation, the analysis of results and the feedback to stations. Particular emphasis will be on correlator-station communication from the station reports and logs to correlator feedback. Representatives from the correlators will be available for discussions and advice on issues regarding your station.


Seminars are presentations including demonstrations to an audience of 10 or more people, depending on the topic.

Teachers: Bob Campbell

Experience level: Beginners; some new material.

Description: This seminar will cover the concepts of antenna pointing and amplitude calibration, with an underlying ambition to provide the context for how such calibration efforts that you would carry out at the station would be used by the astronomer (or geodesist) when they come to make images of their observed sources.  We will review the physical basis of system temperature, gain, and SEFD, as well as how they relate to each other.  We will sketch various methods to measure these quantities, and review some illustrative plots.  The talk then shifts to the basics of the field-system implementation of these concepts, and walks through the contents of RXG files and how to use the ANTABFS program to prepare the files that the astronomer would in turn from their point of view treat as the a priori calibration data.  We hope to finish with some examples of how calibration errors can affect the resulting source images.

Teachers: Katie Pazamickas, Rick Hambly

Experience level: Beginners with some Advanced material; class contains new material.

Description: This presentation will provide an overview of the use of high-accuracy time and frequency in VLBI. This will include a discussion of all the “clocks” used in VLBI (Hydrogen Masers, GPS timing clocks, the clocks inside the Field System computer and the clock information needed by the correlators) and how they need to be tied together in order to guarantee successful VLBI measurements. Some focus will be put on the different types of masers with block diagrams as well as generalized operational procedures.

Teachers: Alexander Neidhardt

Experience level: Beginners and Advanced.

Description: This course describes how to write station specific code with C and C++. We discuss how other programs can easily interact with the FS or what is required to implement your own control loops outside of the FS supporting tasks required by the FS.

Teachers: Gino Tuccari, Sven Dornbusch

Experience level: All levels; some new material.

Description: This seminar will give an introduction into the setup and operations of the digital backend DBBC3. There are three different modes available: DSC, OCT, and DDC. We will give a description of those modes and their main observing applications. In its digital down conversion mode, the DBBC3 is in the process to be fully integrated into the Field System and a number of IVS stations started to use the DBBC3 for regular VLBI observations. It will be shown how to install, test, and operate a DBBC3, which is capable of processing a maximum of 8 RF/IF with each 4-GHz bandwidth inputs from different bands and/or polarizations to produce a group of up to 128 output data channels, using four 10GE output connections at a maximum data rate of 8 Gbps each. During the course the calibration process required by the system will be described; this procedure is now fully automated, but it still requires the knowledge and understanding of the process it is performing in order to evaluate the results.

Teachers: Chet Ruszczyk, Russ McWhirter

Experience level: Beginners; new material.

Description: This seminar will give an introduction into the installation and operation of the VGOS compliant R2DBE-G digital backend and the RDBE-G.

Teachers: Jason SooHoo, Simone Bernhart

Experience level: Beginners; some new material.

Description: This course will cover operational aspects of the data transport between stations and correlators either electronically (e-transfer) or physically (module shipment). We will provide theoretical background and cover the e-transfer website as well as packtrack.

Teachers: Marjolein Verkouter

Experience level: Beginners; some new material.

Description: This class will briefly summarise the VLBI data acquisition chain, then shift focus to contemporary high-speed ethernet (packet) recording hardware and some of their technicalities and tools available to record and/or handle the recorded data; introduce the VDIF data format; spend a fair amount of time on the problems with intercontinental large-data-volume transfers over high-bandwidth network connections and solutions to those that have been developed within the VLBI community.

Teachers: Matthias Schartner

Experience level: Beginners; new material.

Description: This module will describe how a VLBI observation schedule is created. We will go through the most common and important scheduling concepts, including tagalong mode. Furthermore, we will have a look at both the scheduling catalogs (to discuss opportunities for stations to improve the models) and the content of the schedule files. Finally, we will be generating some basic schedules using the VieSched++ software. Students who want to follow the exercise actively will need to bring their own laptop with a VieSched++ installation on it. You can also follow the exercise steps passively.

Teachers: Mario Bérubé

Experience level: Beginners; new material.

Description: The VLBI Communications Center (VCC) is intended to provide near real-time, machine-to-machine, two-way communication between VLBI components. The VCC is a web service supported by a database and a message broker using formatted information designed for access by computers. The database keeps up-to-date data on schedules, catalogs, and all relevant information on various IVS components (e.g., station’s availability, latest SEFDs). The message broker is used to inform any IVS components that some data/information at the VCC are relevant for them. The VCC knows who acknowledges the message and uploaded the schedule, allowing full traceability of data/information exchanges. In this class, we will show how the VCC can improve the current communication system and data exchange between VLBI components and provide a demonstration of the VCC. The demonstration is planned to include live antennas running the VCC client software.


Lectures are intended for a general audience. All attendees at the workshop are welcome to attend the lectures.

Teachers: Pedro Elosegui

Experience level: Beginners.

Description: This lecture will describe the VLBI technique from scheduling to data capture, to correlation and to analysis. It will cover the basic concept, observational system, delay resolution function, correlation, and observables.

Teachers: Sara Hardin

Experience level: Beginners.

Description: This course will describe the effect on geodetic data analysis of various problems during data acquisition. Problems such as clock breaks, bad tracks, parity errors, pointing errors, warm receivers, and late starts will be covered. The importance of the stability of the signal chain and the delay of the VLBI signal through it (the so-called “peculiar offset”) will be discussed.

Teachers: Frank Lemoine

Experience level: Beginners; some new material.

Description: An overview of the scientific goals of geodetic and astrometric programs will be presented. Particular emphasis will be placed on reference frames which are the fundamental products of VLBI.

Teachers: Chet Ruszczyk, Arthur Niell

Experience level: Beginners; new material.

Description: In this lecture we will provide a description of the VGOS signal chain (using the Haystack example), including subsystems and the operational model, along with the direction the signal chain will be going.

Teachers: Gino Tuccari

Experience level: Beginners; new material.

Description: The BRAND wideband receiver is being developed with support from the European Union’s Horizon 2020 research and innovation programme as a part of RadioNet. Its continuous frequency range from 1.5 GHz to 15 GHz makes it a scientifically extremely interesting development for radio astronomy. But it also covers the VGOS frequencies and even extends them to lower and higher frequencies. Used for geodesy, this could yield results superior to the ones which will be achieved with the traditional four VGOS bands. It will also allow to retrofit traditional prime focus antennas to become compatible with VGOS antennas in terms of frequency coverage, with a much greater output data rate. Another goal is to model an adequate feed for secondary focus; if successful, this would make the BRAND receivers usable for any VGOS antenna. The first half of the almost 4-year term of the project is over and it is possible to give an overview of the achievements so far and of what is planned for the near future.

Teachers: Frederic Jaron

Experience level: Beginners; new material.

Description: PolConvert is a new tool in the correlator’s toolbox. VGOS was developed by the IVS for high-precision (up to submillimeter) geodesy observations. To achieve the signal-to-noise ratio (S/N) required for such an accuracy, the VGOS antennas are equipped with ultra-wide receivers, covering from 2 GHz to 15 GHz. The VGOS bandwidth makes it necessary to observe in a basis of linear polarization. To maximize the S/N of observables the visibilities have to be combined to Stokes I for fringe-fitting. PolConvert offers a route for this processing step by performing a complex cross-polarization bandpass calibration and the conversion of the visibilities from linear to a circular basis. In addition, PolConvert can take into account a-priori ionospheric data (e.g., from GNSS observations) for the correction of the visibility phases. We will give a general introduction to the concepts of PolConvert and how it can be applied to geodetic VLBI data.

Teachers: Alexander Neidhardt

Experience level: Beginners; new material.

Description: This meeting will be organized as an open round to mention issues and problems at the sites but also to make suggestions over the whole range of IVS. It should be a “suggestion box” for feedback, ideas, and improvements, not only as an operator but especially as seen by station staff.

Teachers: Alexander Neidhardt

Experience level: Beginners; new material.

Description: This lecture explains the IVS Seamless Auxiliary Data Archive. It shows how to participate and how to extract useful information.