| Following the decommissioning of the venerable TADUmax, along with the other backends and the MFFEs, at the end of the eVLBI session on June 24, 2015, a new page has started also in VLBI operations.
To enable the continuation of the WSRT's participation in VLBI arrays, a Digital BaseBand Converter (DBBC) was bought in late 2014 as a dedicated VLBI backend. The DBBC replaced the TADUmax in the sampling and formatting of the telescope IF data prior to recording. At the same time, an MFFE receiver was converted to circular polarization.
The DBBC and the modified MFFE were commissioned in the spring and summer of 2015. In addition, new software was written to interface the telescope steering and frontend controls with the VLBI system as well as a new visualisation system for the Radio Observatory control room.
In the first operational test of the new system fringes were detected at 18cm in the EVN's eVLBI session of September 15-16, 2015 (top left); in the current eVLBI session of October 6-7, 2015, fringes at 6cm are also detected (top right).
For this smooth transition, a lot of work was required. Credits to (alphabetically): Richard Blaauw, Geert Kuper, Hans van der Marel, Jurgen Morawietz, Jurjen Sluman and the crew at the WSRT Henk Bokhorst, Lute van de Bult, Pieter Donker, Peter Gruppen, Jan-Pieter de Reijer, Harm-Jan Stiepel, Albert Wieringh. Special thanks are also due to our colleagues at JIVE, G. Tuccari (INAF) and M. Wunderlich (MPIfR).
Conversion to the new VLBI equipment was realized on a very fast timeline: the WSRT has managed to continue its VLBI participation without missing a single run! The modernized WSRT will first take part in VLBI arrays using a single 25m telescope (RT0 or RT1) at all frequencies provided by the MFFEs as well as the modified 5cm MFFE. The new DBBC also enables broad-band (2 Gbps) WSRT participation as a Tied array at L-band with the 12 dishes that will come into operation with the Apertif PAFs in 2016.