[Paper Review] European VLBI Network: Present and Future

J. A. Zensus, E. Ros|arXiv (Cornell University)|Jan 21, 2015

Radio Astronomy Observations and Technology3 citations

TL;DR

This paper reviews the current status and future prospects of the European VLBI Network (EVN), a collaborative radio astronomy facility spanning Europe, Asia, South Africa, and Puerto Rico. It details the EVN’s evolution from a 4-station array in 1980 to a global network with enhanced resolution, data rates up to 2 Gbps, and participation in major projects like ALMA and RadioAstron, highlighting its role in high-fidelity imaging, astrometry, and multi-wavelength studies of compact radio sources and black hole environments.

ABSTRACT

The European VLBI Network is a collaboration of the major radio astronomical institutes in Europe, Asia, South Africa and Puerto Rico. Established four decades ago, since then it has constantly improved its performance in terms made using resolution, data bit-rate and image fidelity with improvements in performance, and the addition of new stations and observing capabilities. The EVN provides open skies access and has over time become a common-user facility. In this contribution we discuss the present status and perspectives for the array in a continuously changing environment, especially in the era of ALMA and with the Square Kilometre Array ante portas.

Motivation & Objective

• To assess the present operational status and scientific contributions of the European VLBI Network (EVN) as a multi-national radio astronomy facility.
• To analyze the technological advancements in EVN's performance, including increased data bit-rate, improved image fidelity, and expanded station network.
• To evaluate the EVN’s role in the context of emerging facilities such as ALMA, the Square Kilometre Array (SKA), and space-VLBI missions like RadioAstron.
• To outline future development plans, including new telescope additions and the transition of JIVE into a European Research Infrastructure Consortium (JIV-ERIC).
• To highlight the EVN’s scientific impact through key observational achievements in astrophysics, including studies of masers, jets, and galactic nuclei.

Proposed method

• The EVN operates through coordinated long-baseline interferometry using ground-based radio telescopes across multiple continents, with data recorded on-site and correlated centrally at JIVE.
• Observations are conducted in both standard disk-recording mode (three 3-week sessions annually) and real-time e-VLBI (ten 24-hour sessions annually), with additional out-of-session scheduling for urgent targets.
• The network uses digital backends and the SFXC software correlator to achieve data bit-rates up to 2 Gbps, enabling high-fidelity imaging and astrometric precision.
• Joint observations are conducted with major facilities such as the VLBA, Green Bank Telescope, phased Jansky VLA, and RadioAstron, enhancing dynamic range and angular resolution.
• Scientific data are processed and analyzed through the JIVE data center, supporting transnational access and collaborative research under programs like RadioNet3.
• The EVN leverages high-sensitivity, large-aperture antennas (e.g., Effelsberg, Sardinia-64m, Tianma-65m) to study faint and compact radio sources, including methanol masers and young supernovae.

Experimental results

Research questions

• RQ1 How has the EVN evolved in terms of station distribution, data bit-rate, and image fidelity since its founding in 1980?
• RQ2 What is the role of the EVN in supporting major international projects such as ALMA and RadioAstron, particularly in millimetre-wave and space-VLBI experiments?
• RQ3 How does the EVN contribute to high-precision astrometry and the study of compact radio sources, including black hole environments and maser phenomena?
• RQ4 What are the future expansion plans for the EVN, including new telescopes and infrastructure developments such as JIV-ERIC?
• RQ5 How does the EVN maintain scientific relevance and sustainability in the era of the Square Kilometre Array and next-generation radio telescopes?

Key findings

• The EVN has evolved from a 4-station network in 1980 to a global array with 14 major institutes and over 20 participating telescopes, including 64-m and 65-m dishes in Sardinia and China.
• Data bit-rate has increased from 4 Mbps (Mk II system) to a planned 2 Gbps (Mk V system), significantly enhancing image fidelity and dynamic range.
• The EVN has produced hundreds of refereed scientific publications, with high-impact studies on compact symmetric objects, methanol masers, gravitational lenses, and jet structures in radio galaxies.
• Joint observations with ALMA and RadioAstron have enabled high-resolution imaging of the immediate vicinity of supermassive black holes, such as in the Galactic Centre and M87.
• The transition of JIVE into a European Research Infrastructure Consortium (JIV-ERIC) in 2015 ensures long-term sustainability and expanded transnational access for EVN users.
• Future additions, including the FAST 500-m telescope in China, the Qitai 110-m telescope, and a potential African VLBI array, will significantly improve baseline coverage and sensitivity at centimetre wavelengths.