e-VLBI, or electronic Very Long Baseline Interferometry, uses fibre optic networks to connect radio telescopes to a central data processor, which correlates the data from the telescopes in real-time. The astronomers can inspect their results almost immediately. In classic VLBI the data are recorded on disks and shipped to the correlator for processing, which can take weeks.
e-VLBI is the obvious choice for studying transient events such as supernova explosions and gamma-ray bursts; follow-on observations can be triggered in time, also in other spectral regions. But e-VLBI is not only quicker, it is also easier to organize once the procedures are clear. So, it could become the standard way of doing VLBI.
Through the EXPReS project (2006-2009), the EVN correlator at JIVE was upgraded for e-VLBI operations, up to 16 telescopes at a time, 1 Gb/s from each telescope; the same capacity as for classic VLBI. As a result of these upgrades, the EVN now offers regularly scheduled e-VLBI sessions, as well as opportunities for target-of-opportunity observations.
The NEXPRes project (2010-2013), also coordinated by JIVE, addressed the existing bottlenecks of e-VLBI which prevented it from being used for all EVN observations. Among other activities, NEXPReS developed high-speed recording/transmitting capabilities which now allow for data re-correlation and remove the distinction between disk-based and electronic VLBI.
For more information about JIVE's contributions to the development of e-VLBI, watch JIVE: Forging a Path to the Future of Radio Astronomy (15 minutes, 387 MB mp4, best viewed with VLC).
The following links provide some information about the current e-VLBI capabilities and status.