The radio domain covers wavelengths ranges from meter to (sub-)mm, corresponding to a range of about 100 MHz to a few hundred GHz in frequencies. The longer wavelengths are typically dominated by incoherent synchrotron emission or coherent processes, with thermal emission becoming more important at short wavelengths.

High-energy transient phenomena (supernovae, gamma-ray bursts, compact object mergers, flaring AGN, tidal disruption events etc.) are generally sources of non-thermal synchrotron emission; the radio emission traces relativistic particle populations generated in e.g. shocks. While timely observations are important in this domain, it must be noted that radio emission is often synchrotron self-absorbed initially while the emitting region is very small.

Radio data are often used to constrain the size of the emitting region either by direct measurements (through very long baseline interferometry [VLBI], in which case radio telescopes networks on global scales work together), or by detecting scintillation. The high angular resolution of VLBI -typically milliarcseconds- often allows direct measurement of proper motion and constraining geometry, sometimes even the distance (for Galactic transients). Measurements of radio spectral indices and polarization may help characterize the emission process and the physical conditions in the emitting region. Examples for coherent radio emission from transients include Fast Radio Bursts (FRB).

The Radio JCE nodes are organized around the four radio facilities in ACME: Effelsberg, ASTRON – Science Data Center Operations (SDCO) – for LOFAR/ILT support, e-MERLIN, and JIVE, a European Research Infrastructure Consortium to support the EVN. The expert support at these nodes include help with proposal preparation (the instrument-specific technical details; how to submit a proposal), observe file preparation (preparation for an experiment), conducting the observations, preparing the data for the user (calibration metadata, data reduction pipelines), help with data analysis, help navigating archives and using the various tools provided. Our aim is to offer expert help to all users, regardless their experience level working with radio data. 

For the services offered by each JCE, please refer to the individual node pages. If you have general questions about radio facilities in ACME or have specific questions about any of the instruments or their use, please feel free to ask through the ACME virtual platform. General questions will be answered centrally, while instrument specific questions may be forwarded to the relevant node.