eVLBI

eVLBI (electronic Very Long Baseline Interferometry) is a technique that allows radio telescopes around the world to cooperate as a single, Earth‑sized aperture by transmitting data in real time via high‑speed networks to a central processing centre. Unlike traditional VLBI, where recorded data are shipped on physical media, eVLBI streams raw telescope data over fibre or satellite links, enabling near‑instantaneous correlation and imaging. This greatly reduces the time between observation and scientific output.

The concept was first demonstrated in the late 1990s, when several European telescopes participated in a “pilot” eVLBI experiment. Since then, large global arrays have adopted the method, including the European VLBI Network, the Very Long Baseline Array in the United States, and the Long Baseline Array in Australia. The MeerKAT and the Australian Square Kilometre Array Pathfinder (ASKAP) are also capable of participating in eVLBI sessions, providing high sensitivity at centimetre wavelengths.

Key technical developments for eVLBI include the deployment of high‑capacity fibre links (often exceeding 10 Gbps) and the use of robust data loss mitigation schemes such as forward error correction. Software correlators running on modern computing clusters or GPU‑accelerated platforms process the data streams in real time, producing calibrated visibility datasets that can be immediately archived and analysed.

eVLBI has enabled several scientific milestones, such as rapid response observations of transient phenomena, high‑resolution imaging of active galactic nuclei jets, and monitoring of spacecraft radio signals. Its continued evolution, including integration with next‑generation facilities like the Square Kilometre Array, promises to deepen our understanding of the radio universe.