Networks of radio telescopes can be used to produce detailed radio images of stars and galaxies: the resolution of the images depends on the overall size of the network (the maximum separation between the telescopes) and the sensitivity depends on the total collecting area of all the telescopes involved and, crucially, the bandwidth of the connection between the telescopes. In principle, all these networks can make wide-field images (several arcminutes across), but for the larger networks, the maximum field-of-view is limited in practice to several arcseconds by the output data rate of the correlator which combines the signals from the different telescopes and the processing power required to analyse the enormous data sets that would be produced. Ultimately, the productivity of these telescopes depends on the level of access and user support and the ease with which an astronomer can go from the data as received from the telescope to scientific results which form the basis of publishable research. Various aspects of are aimed at maximising the scientific capabilities and productivity of European radio telescopes: the TNA programme addresses user access and support, and capitalises on the progress in automating the data processing required. This has used a scripted pipeline approach based on existing software, much of which dates back many years. The focus of this Joint Research Activity is to develop the algorithms and tools to extend this approach to the next phase in the development of radio telescope networks, which involves a massive increase in data volumes.
The European VLBI Network (EVN) brings together European radio telescopes to form potentially the most powerful radio telescope in the world (in terms of resolution times sensitivity). Realising its true potential, however, involves replacing the fragile data recorders, which have already been pushed past their original specification by an order of magnitude, with real-time optical fibre connections and increasing the output data rate of the correlator. The development of disk-based recording is a necessary step in this process and is underway. Similarly, the UK operates a unique long-baseline network, MERLIN, which uses radio-links to connect seven telescopes across England. This fills the gap between the EVN and smaller single-site arrays such as the VLA in New Mexico, or the WSRT in the Netherlands. Replacing these links with optical fibre connections and installing a new correlator will boost the sensitivity of MERLIN by an order of magnitude. All these upgrades are now in progress: Dante/GÉANT are helping with the first proof-of-concept experiments with real-time fibre connections between EVN telescopes; the EVN and WSRT correlator upgrades are being commissioned and the e-MERLIN project is underway. In each case, the upgrade is aimed at maximising the scientific capabilities of the instrument using the existing basic infrastructure, namely the radio telescopes themselves.
However, these ten-fold improvements in sensitivity and field-of-view necessarily involve an increase in raw data volumes delivered to the astronomers by more than two orders of magnitude. To really take advantage of these improvements and to allow astronomers to produce scientific results from these unique European radio astronomy facilities more quickly, more reliably and more creatively, will require innovative algorithms to provide better calibration and imaging capabilities as well as new approaches to handle the huge volumes of data in a more advanced way.
This Joint Research Activity will investigate and implement new calibration methods and develop efficient and scalable processing techniques. This software development is an essential part in enabling astronomers, both in Europe and world-wide, to take advantage of these next generation European radio astronomy research facilities.
The ALBUS Principle Investigator is H. van Langevelde (JIVE)
More information can be found on the wiki page ALBUSWikiPage.