1. Technology and the Future of the EVN
Arpad Szomoru

2. Visions of the future Science vision for the EVN
Including a chapter on technology
2015 seemed safely remote
At the time...
Exercise is being revisited
Part of the Jumping JIVE project
Presentation by Lindqvist

3. Recommendations in 2007
Extend the IF bandwidth at the telescopes to at least 1 GHz. Use digital base-band converters (dBBC), with 8-bit sampling (if feasible) and RFI mitigation. Recording systems capable of handling up to 256 Gb/s
Expansion of EVN below 1 GHz, at 6 GHz, GHz, 22 GHz, 30 GHz, 43 GHz and 86 GHz
High surface-brightness sensitivity at frequencies below 1 GHz
New broad-band dual-polarization receivers at cm wavelengths, up to 1 GHz bandwidth in C-band and higher. Frequency agility is required between at least a sub-set of important continuum bands, e.g. L, C/X, and K-band
Additional telescopes to improve the EVN2015 sensitivity.

4. Recommendations in 2007 (continued)
Multiple Gb/s connection of the telescopes to the correlator would allow very high-sensitivity and robust real-time operations for extended times, without disk space limitations at the stations. This is especially required for transient observations, and 24-hour coverage by multi-network VLBI observations
Seamless EVN-MERLIN integration as the shorter baseline core of EVN operations can be achieved with a 32 Gbps connection from one EVN telescope into the e-MERLIN system and multiple Gbps connections of e-MERLIN telescopes into the current EVN correlator at JIVE
A new generation EVN correlator at JIVE with a capability of up to 256 Gb/s per radio telescope for routine network operation with 32 station capacity to accommodate all network related stations. The requirements also accommodate very high spectral resolution as well as time resolution experiments
Further opportunities need to be explored for space science related activities
The development of software tools for new and improved data products, advanced data reduction pipelines, Grid applications, and Virtual Observatory applications, leading to improved astrometry, phase-referencing procedures, and high- and low-frequency calibration procedures

5. Recommendations in 2007 (continued)
EVN to continue to support and enlarge the user community by means of teaching networks, workshops, symposia, and PR activities. Improved data calibration pipelines and VO capabilities will attract more users from outside of VLBI institutes
Maintain a certain fraction of over-subscription in order to assure that the best science is done and a wide range of topics is covered. Improved/simplified procedures may be necessary to deal with an increasing number of triggered and Target of Opportunity projects
More frequent EVN sessions in support of monitoring programs. The EVN should be more flexible toward projects that require coordinated observations with other instruments, and should accommodate rapid response science runs with the possibility of immediate feedback
The EVN needs to develop optimal complementarity for the SKA. The EVN should serve as a technology test bed for SKA
A high priority for spectrum management at all EVN stations and for further development of RFI mitigation techniques is essential
The EVN2015 should ultimately aim for developing a real-time VLBI network on global scales

6. The future in 2007 Telescopes
IF bandwidth of the EVN stations to 1 GHz in the L-band, and to 2-4 GHz in the C-band and higher
Full digital sampling of Ifs (dBBC project)
Higher bit sampling (up to 8 bits) for RFI mitigation
Rapid switching time between frequency bands on timescales of few seconds
Continuous monitoring of telescope performance during the experiments
Rapid data analysis as well as on-the-fly changes in the observing schedule
Transfer of calibration data from the telescopes to the correlator in real-time
Data from co-located WVR radiometers and GPS receivers for the atmospheric and ionospheric phase calibration, respectively
Installation of dual-feed receivers on the smaller dishes. Even better, focal plane arrays
New telescopes in strategic places (e.g. North Africa)
New full EVN members: Latvia (32m), Evpatoria (70m), Simeiz (22m), Miyun (50m), Kunming (40m), Yebes (40m), and the Sardinia telescope (64m).

7. The future in 2007 (continued)
Correlator
Correlator capable of processing data from 32 stations in real-time
16 Gsamples per second at 8-bit sampling.
up to 128 Gbit/s per telescope, or 4 GHz per bandwidth in both polarizations.
Spectral line experiments with16000 channels per correlation product with floating point accuracy
mapping of the full primary beam of a 25-m antenna in standard operations
Logistics
e-VLBI observing with ad-hoc global arrays including telescopes with various backend systems will be straightforward
Post-processing
Robust and reliable pipeline, providing maps as well as calibrated data.
Data archive with smart selection for data-mining
Virtual Observatory tools to help provide data products
light curves, spectra, pulsar time series, or overlays of images with results from other instruments.

8. And here we are in
Previous recommendations were perfectly sensible
And many of them (unfortunately) still are totally relevant
Roadmap was rather ambitious
How to proceed?
Jumping JIVE to the rescue!
Presentation by Lindqvist

9. Current status New telescopes
Irbene, Yebes, SRT, Kunming fully operational, KVAZAR and KVN networks have joined
Westerbork was lost due to APERTIF
High-bandwidth receiver system under development
BRAND
New backends
DBBC2 in use, early version of DBBC3 available
IAA, ShAO, KVN, JPL, Haystack Obs all have developed backends
Higher bandwidths, increased operational reliability, but compatibility may become an issue
Multi-frequency receivers in KVN (22, 43, 86, 115 GHz)
Partial system at Yebes (22/43 GHz)
New design created, smaller, easier to deploy at other stations?

10. Current status (continued)
Multiple 10G and 100G connections have become standard
At least across Europe
Disk shipping nearly obsolete thanks to e-shipping
Two complete EVN sessions recorded on FlexBuffs
Semi-automatic data transfer
Great simplification of logistics
e-MERLIN has re-joined EVN!
Both recorded and real time
Software correlation has opened up many new features
Flexibility, scalability
Next step, GPUs? Presentation by Phillips
Many improvements in the past years:
Correlation capabilities and data transport
Many new stations
Sensitivity of EVN has lagged
Observing bandwidth limited to 256 MHz, only twice that of 11 years ago...

11. New telescopes, increased sensitivity and fidelity
Newly built or to-be built
FAST 500m (China), QTT 110m (China), NARIT 40m (Thailand), MeerKAT (South Africa) and the proposed 30-40m radio telescope in the United Arab Emirates
Refurbished telecom antennas
Goonhilly 26m (UK), Usuda 64m (Japan), Sao Miguel 32m (Portugal), the Hellenic telescope 30m (Greece), Kuntunse 32m (Ghana), Xi’An 40m (China) and ROT 54m (Armenia)
Geodetic 13.2 m telescopes
Ny Ålesund, Wettzell, RAEGE Santa María, RAEGE Gran Canaria
Not straightforward due to limited time availability.

12. What more is needed/wanted?
Enhancement of real-time capacity of the EVN
4, 8, 32 Gbps (?)
e-MERLIN, KVAZAR for short and intermediate baselines
Sardinia for sensitivity
Correlator upgrades
More connectivity
More computing power: FPGAs, CPUs, GPUs, all of these?
Sufficient recording capacity to combine real-time and delayed processing: difference between e and recorded vanishing
EVN light?
Has been talked about for many years
Quick response to transient events
Bound to become more important
UV coverage EVN + eMerlin at 6cm, 18 stations

13. (Much) wider bandwidths
BRAND now under development
Feed + receiver
1.5 – 15.5 GHz
DBBC3
Geodesy: 4 * 1 GHz
Range of 2 – 14 GHz
Investigation into secondary focus options
Will produce implementation document
Including list of suppliers/industrial partners

14. Universal backends
Make VLBI just one of many different observing modes
Switchable within minutes
Separate sampling from rest of processing
As much RF or IF as possible
Maybe after course sampling, store into VDIF packets
Connect to various compute clusters via fast ethernet switch
Several presentations at this workshop

15. RFI Radio Frequency Interference (RFI): severe global problem
which will worsen in the future
will require action from the EVN to mitigate its effects
major concern for all observatories
may jeopardize the investments to achieve better sensitivity and wider frequency coverage
Continuous monitoring at the EVN stations. Small antennas covering the frequency interval between 1 and 18 GHz and capable of moving in azimuth and elevation would be a necessary investment to identify the source and frequency of the RFI.
The installation of High Temperature Superconductor filters prior to the cryogenic LNAs to avoid the saturation of wide band amplifiers.
An increase of the number of bits to digitize the recorded signal to avoid saturation. Traditionally VLBI has used 2 bits but the presence of strong RFI signals advises the usage of 8 or 10 bits.
Legal measurements to prohibit the usage of the electromagnetic spectrum in the vicinity of the observatories.
A global policy defended by the CRAF.
RFI flagging prior to correlation using advanced algorithms.
Presentation by Baan

16. Software for a global array
Scheduling:
Could (should) be far more flexible
Optimise use of resources, respond to changing circumstances.
Rapid response to transient events, needs further automatisation
Transparent global scheduling
Software:
re-factoring of SCHED
Easier scheduling of different hardware, different versions of firmware
Ongoing worry: Field System
Aging, not under our control
Depending on the kindness of strangers
VLBI with CASA
Make VLBI data reduction (and science) more accessible to new generation of astronomers
Integration into notebooks like Jupyter
Bring compute to data
Monitoring of arrays:
Effort at Wettzell to come up with “universal” web-based system
Making use of existing monitoring systems

17. Expectations Five years
Wide-band receivers on at least a sub-set of the EVN. What frequency range will be covered is unclear, and will no doubt partly depend on the performance and price of BRAND, partly on specific science cases. Aiming for maximum sensitivity by using all of the band will of course bring its own set of problems, in terms of availability of media, connectivity, correlation capacity.
At higher frequencies, multi-band receivers like the KVN quasi-optics system on a sub-set of the EVN.
DBBC3 backends (or comparable) at all stations
RFI mitigation at the stations (in-built feature of DBBC3)
Multiple 100G connectivity to JIVE
Inclusion of KVAZAR telescopes in real-time operations
Inclusion of all eMerlin telescopes at high bit rates in both recorded and real-time operations, greatly improving UV coverage on shorter baselines
Inclusion of Ghana, Xi’An, MeerKAT telescopes
Real-time observations using the JIVE UniBoard Correlator (up to 16 stations at 4 Gbps, or 8 stations at 8 Gbps)
Regular correlation of geodetic observations at JIVE
(semi-) Automated follow-up of transient events by sub-set of EVN stations
EVN – light observations, more regular observing sessions with the EVN stations that are not heavily oversubscribed
Upgraded scheduling and common monitoring tools.

18. And further along Ten years
“Real” global VLBI, seamless cooperation of different networks
Global VLBI with the SKA
Deployment of “Software Defined Radio” backends, to some degree doing away with the need for different hardware backends for VLBI, pulsar astronomy, etc. Such a system would isolate the digitisation step from the rest of the backend, sampling the RF signal, or IF, and packaging the samples into VDIF packets. These VDIF packets can be stored for later processing or processed on the fly by any suitable piece of equipment, connected via Ethernet. A similar system is currently being considered at the VLBA
True wide-field VLBI, enabling high-resolution blind surveys
Use of solar collectors as radio telescopes
Upgraded software control tools for telescopes and backends.