SKA-NL Roadmap: SaDT and VLBI. Arpad Szomoru, JIVE

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1 SKA-NL Roadmap: SaDT and VLBI Arpad Szomoru, JIVE

2 JIVE - Joint Institute for VLBI ERIC Promote and advance the use of VLBI for astronomy Central correlation for European VLBI Network Operational feedback to stations User support Preparation of observations Data reduction Improvement of VLBI technique in general Base budget from partners in 8 countries: China, France, Germany, Italy, Spain, Sweden, United Kingdom, the Netherlands, South Africa European Research Infrastructure Consortium (ERIC) since 2015 hosted by ASTRON

3 How the EVN stations view feedback from JIVE

4 Projects No R&D budget R&D financed through EC and NWO projects 2006 EXPReS SA1 SA2 JRA NWO-SCARIe 2009 NWO-ExBox RadioNet0FP NWO-ShAO;collaboration NEXPReS UniBoard ALBiUS SA1 SA2 JRA1 JRA RadioNet3 UniBoard^2 Hilado 2014 BlackHoleCam WP1.1 WP1.3 NWO0SKACNL0roadmap SaDT:0SAT0architect SKA-VLBI 2015 H20200ASTERICS Cleopatra Obelix NWO;KAT7-VLBI Not counting Space Science projects!

5 SKA-NL Roadmap proposed activities SKA Signal and Data Transport (SaDT) Associate member of consortium Already involved, albeit at a modest level Relevant expertise at JIVE Aperture Array Verification Systems UniBoard benchmarking Plenty of UniBoard expertise in-house Based on assumption that UniBoard would be used for testing AAVS And that UniBoard 2 would find its way into the LFAA correlator design Both reasonable assumptions Both turned out untrue

6 SaDT work at JIVE Provide Synchronisation and Timing (SAT) architect Direct request from SaDT consortium Paul Boven, Network/Linux specialist at JIVE 40% position Support the SAT group and provide effort in the following activities Coordination with members of the SAT team and SADT Coordination with other Elements in defining ICDs Coordination with the SKA Architecture group Design of the UTC distribution system Provide support during upcoming PDR and CDR

7 Time and frequency transport: White Rabbit White Rabbit Developed at CERN Achieve sub-ns accuracy in the synchronization of around 1000 nodes, up to 10 km distances Built on Precise Time Protocol (PTP) and Synchronous Ethernet Open source software, firmware and hardware Selected for time distribution in SKA-mid Need to measure timing performance on longer distances And in different climates Use WR-Zen board (SevenSolutions) First tests 10km fibre in climate chamber 24.4 km dark fibre Dwingeloo WSRT In situ, at Meerkat site

8 On-site testing

9 Desolation and fibres

10 The setup Losberg Farm Losberg Core Site KAPB LC Equipment room MeysDam Farm E2000 APC 48 Core Duct Cable LC 223m CMC Container 3 470m E2000 APC E2000 APC 4 580m E2000 APC m m 48 Core Duct Cable 24 fibres terminated Fibres 1 48 MeerKAT Fibre Network Fibre Splice Diagram Rev. 1 Legend Splice / Joint Fibre Patch Panel Fibre Lengths Klerefontein Server Room 2 Fibres E2000 APC E2000 APC 48 Core Duct Cable Fibres Fibres Core Duct Cable Fibres Fibres Fibres m Pole Core Duct Cable Pole Core Duct Cable Fibres Fibres 1 24 Fibres E2000 APC Carnarvon POP Site Pole Core MASS Cable Pole 163 MASS Fibre Cable attached to powerline ADSS Fibre Cable through town

11 First results WR system measures the total round trip time determines one way delay between master and slave (taking dispersion into account) steers the PPS on the slave to be at the same time as the master. Top panel: PPS error between -0.1 to 0.2 ns clearly exceeding the WR specifications. PPS error: difference in arrival time between the pulse generated by the WR-master and WR-slave Second panel: temperature measured by the C-Bass telescope weather station at Klerefontein. Interesting variation in weather, including thunderstorms with hailstones up to 2cm in size. Third panel: fibre round trip time in ns, as measured by WR. The total link delay varies by more than 50ns in the measurement period. The correlation between outside temperature and link delay is obvious.

12 SKA-VLBI The SKA has formed a number of science working groups receive feedback from astronomers on the design process of the SKA. covering the main scientific areas (Epoch of Reionisation, Pulsars, Transients etc.). Informal 'VLBI focus group' formed to inform thevlbi community At the 'Advancing Astrophysics with the Square Kilometre Array' conference in 2014, it was realized that adding VLBI capabilities would significantly broaden its science case VLBI focus group was transformed into a formal SKA working group goal of providing fundamental input to the various levels of scientific and technical requirements.

13 SKA-VLBI (2) SKA System Requirements now include a SKA VLBI mode At least 4 beams for VLBI usage: one for target and three for calibrators VLBI beams will be generated from sub-arrays by up to 100km SKA will produce VLBI beams at suitable bit representations and bandwidths all subsequent processing is not considered part of the SKA design Will be addressed by this task Modifications to the SFXC correlator at JIVE Developments in data reduction tools.

14 SKA-VLBI activities Practically all VLBI data reduction still done using AIPS. Has been around for a very long time Still being actively used by many astronomers Not anymore of this day and age Dwindling software support Huge amount of effort to insert modifications or new functionality Outdated architecture After careful consideration, CASA appears best candidate Active support, sustained through use for ALMA data reduction Modern architecture, Python-based interface Extensive database with examples for data reduction Although some issues with speed?

15 SKA-VLBI activities (2) Modifications of the correlator code Allow the use of separate calibrator beams. Application of primary beam corrections CASA-specific, complementing work for BlackHoleCam Fringe fitting (both Cotton-Schwab and HOPS methods) Remove assumption that arrays consist of (nearly) identical elements. Three more will be deployed to participate in in-beam calibration with the other elements of the VLBI array. Adaptations to the correlator code and additional bookkeeping in data processing will be needed. Fix the assumption that system temperature measurements are provided on a uniform grid for all array elements Support for user-provided gain curves Tools for polarization basis conversion will be needed