The LOFAR Network
The six German LOFAR stations (GLOW stations) are connected round-the-clock to the central processor in Groningen by fast glass fibers operating with 10-Gbit/s Ethernet. As gateway serves the Jülich Supercomputing Center (JSC) at the Forschungszentrum Jülich GmbH, where the lines from the six GLOW stations are combined onto two 10-Gbit/s lines. Most of the time these and the other international stations are operated as part of the full LOFAR array, the International LOFAR Telescope (ILT).
Single Station Operations
During times when the international stations are not needed for observations with the LOFAR array, they are available for single station operations. For the German stations this is done since December 2013 in the so called GLOW mode.
Because the network lines of all GLOW stations go via the JSC, all German stations can easily be connected via a common virtual network (VLAN). Dedicated interface computers installed at the stations allow their control and the transport of the data via the same VLAN. In principle, each station owner is able to operate several stations and record their data, limited only by the bandwidth of the network connections. Currently the central control servers for managing the interface computers and for running the observations are located and maintained at the MPIfR Bonn. Data recording computers are hosted at the MPIfR Bonn and the JSC, allowing to record the data with full bandwidth from all GLOW stations in parallel. The GLOW mode is used mainly for pulsar observations with several stations in parallel.
The Long Term Archive
LOFAR started its science operations in December 2012. Several tens to hundreds of Terabytes of data are produced day by day by the more than 50 LOFAR stations in Europe. Even after processing at the ILT observatory in Groningen several Terabytes of data need to be stored in the archive each day. This task is shared by several computing centers in Europe. The German share of the Long-Term-Archive is covered by the JSC, which provides as of 2015 a storage capacity of 290 Terabyte on disk and 6.4 Petabyte on tape. A growth rate of 2 Petabyte/year is planned. This allows fast and efficient access to LOFAR data for the international community of radio astronomers.