PoS(EXPReS09)029

http://pos.sissa.it tested tested - with an is nearing completion n NRC-CNRC is crucial tor, tor, being built by the

ill have a major impact in y y a report on the current successful successful call for Legacy s and baseline (correlator) formation and through all ell Bank . Observatory. Bank ell nd nd fringes shortly after. I will the links,data the phase cohering alaxies at high redshift. This paper at redshift. This high paper alaxies reAlike Licence. nterferometry: The 8th International e-

y of Manchestr

the Creative Commons the Creative Attribution-NonCommercial-Sha

ralph.spencer@.ac.uk The upgraded MERLIN array of telescopes (e-MERLIN), discussof some the features, design in particular with operations expected in Dominion early Observatory of the 2010. Canadia The correla autocorrelation spectrum being obtained in April, a system and the interface to VLBI. The results of a to the performance of the instrument. Station boards board have been delivered. Signal paths have been observing proposals will be summarised, and finalll progress and future plans will be given. e-MERLIN w high resolution radioastronomy, in fields from star stages of stellar evolution, tostages evolution, the of of g stellar formation is presented on behalf of the e-MERLIN team at Jodr team e-MERLIN the of on behalf is presented VLBI Workshop - EXPReS09 Science and Technologyof Long Baseline Real-Time I Madrid, Spain June 22-26, 2009

Ralph Spencer Ralph Spencer Jodrell Bank Centre for , The Universit Oxford Rd, Manchester, UK E-mail: Progress and Status of e-MERLIN of Status and Progress

Copyright owned by the author(s) owned of the Copyrightby terms under

PoS(EXPReS09)029 nd 5-7 GHz Ralph Ralph Spencer Jy sensitivity crucial µ Jy r.m.s. in 1 minute, µ ce give 150, 40 and 10 mas The sensitivity and resoution olution olution and

s, and shows how it fills the gap ance, the receiver system, data links. MERLIN array MERLIN run by the University e e correlator is built on the WIDAR o 2 GHz is made possible through the spectively. spectively. The wide bandwidth of e- itivities itivities of ~30 nce, however the main improvement in in lower fidelity for extended source Figure 1 of e-MERLIN compared instruments. with other

d and 30 arcmin at L band), though the ly ly the current status and future plans are e the incoming digital signal is split into ting ting the 7 MERLIN telescopes to the new increase in in over bandwidth that available correlator correlator will wide allow outimaging field Science Science and Technology Facilities Council. e Lovell 76-m telescope in the array results Galaxy and at regions kpc-scale z~1. Figure Hz. Hz.

2 Jy in deep fields. Spectral imaging over 1.3-1.7 a µ

The following sections discuss the expected perform The baselines in e-MERLIN extend to 217 km, and hen The e-MERLIN The project e-MERLIN [1] is a major toupgrade the e-MERLIN e-MERLIN has a unique combination of 50-150 mas res Jy in typical runs and sub µ components, components, as is currently the case for MERLIN. Th gives improved gives u,v coverage (figure 2) and the new to the HPBW of a 25-m telescope (9 arcmin at C ban missing short spacings in the coverage will result (WIdeband Digital ARchitecture) principle [2] wher 2.Expected performance performance 2.Expected 1. Introduction 1. Introduction e-MERLIN to inresolve processes star-formation AU-scale our 1 shows how e-MERLIN compares with other instrument bewteen the EVLA and eVLBI. and eVLBI. EVLA the bewteen the interface to e-VLBI and Legacy progammes. Final described. resolution at L[20cm], C[6cm], and K[1.3cm] band re MERLIN and new receivers will result in C-band sens of Manchester as a National Facility for the UK’s New New low-noise receivers improve the system performa tosensitivity sources a comes continuum from huge MERLIN. MERLIN. The increase from 14 MHz per polarisation t use of a purpose-built optical-fibre network connec correlator correlator at Jodrell Bank Observatory. Including h at 5 G in senstivity improvement ~30 offactor in a ~2 PoS(EXPReS09)029 Ralph Ralph Spencer ign ign makes extensive use of field system, but this proved far too mediate mediate frequency (IF) and local each with more than 512 channels xtensive xtensive shielding to avoid locally eceiver eceiver at C band) required a entirely excess excess of the currently (or even in the ations) ations) is digitised to 3 bit precision, ove ove the astrometric performance of the ator is via the same station board design Aperture plane (u,v) coverage (upper) d signals are digitised at 1 Gsamples per o into the station board where the light is ble in functionality. inble functionality. ]. ]. The number of channels, polarisation, aximum capacityaximum of the use correlator.The producing producing a total ratedata of 16 and Gbps links in the UK. We initially investigated produced. These require the signals to be ing ing and formatting. Three 10 Gbps optical ed, ed, using leased dark fibre where possible further processed. processed. further with JBO are very JBO with in are similar very to design those

ore ore being down converted to the 2-4 GHz IF give give much higher spectral resolution with up two two of the channels optical are used The here. ICRF. ICRF. where each electro-absorption laser (EML) is

Figure 2 and point spread function (lower) for MERLIN (left) and e-MERLIN (right) at C band total bandwidth. GHz with 2 3

The digital data rates used by e-MERLIN are far in In In spectroscopic mode it has 16 placeable sub-bands Signals are digitised at the telescope, requiring e The provision of wide bandwidth (e.g. a 4 – 8 GHz r next few years) available capacity of the academic managed managed bandwidth solutions when designing the link expensive. expensive. Instead a dark fibre solution was achiev digital systems, designed by NRAO in digital NRAO designed by systems, collabration used for ALMA and the EVLA. The input to the correl being before deformatted data the and photodetected induced induced RFI. Each 2 GHz wide IF band resulting in 24 (in Gbps, 30 becoming Gbps after encod 2 polaris channels are used to transmit the data in parallel, modulated in non return to zero (NRZ) format. L-ban second to cover bandwidththe 8 using 512 MHz bits, 20 Gbps after etc., encoding thus only effectively as the EVLA, where 3 fibres each carrying 10 Gbps g up converted before amplification and filtering bef new new design for MERLIN’s receiver systems. oscillator systems have New been designed and inter are being samplers. the to input for suitable 3. Receiver System and Links3. Receiver e-MERLIN 16x128 MHz bands before further processing. The des programmmable gate arrays (FPGAs) and is very flexi is very and (FPGAs) arrays gate programmmable per sub-band per polarisation. Re-circulation will to 131072 channels per sub-band per polarisation [1 to the with respect mas 1 < the of with goal array, and bandwidths can be mixed and traded up to the m of GPS meaurements of troposphereic delay will impr PoS(EXPReS09)029 Ralph Ralph Spencer Schematic of the e-

Figure Figure 3 MERLIN optical system. data link The previously installed red fibre, the leased blue shows connections the new to dig the telescopes. MERLIN The optical design was done by staff at JBO, all fibres maintenance are being performed providers the commercial by leased with reference radio frequency signal (at efford and ) are done by Fujitsu Telecommunications em. em. The signal is used to lock a high C am bridge ing ing pico-second stability, but has to be ch is on a separate telecommunications d field tests show that use of the phase e e signal is coded, pulse and re-transmitted hannels on a fibre. The data flow is one- peak peak to peak changes of several nsec in a fibre fibre optics using the installed fibre instead opes. opes. In total there is 670 km of fibre with ope ope site from JBO where the transmitter is P eterboro long long (>10 sec) time constant and so short and fibre links showing the superior stability N ottingh am d out. The diference in phase between go and d of driving antennas works well [5]. 4 Figure go and return signal. signal. return and go bre mostly provided by Global Crossing [4]. Crossing Global provided by mostly bre correct the astronomical phases for slow path

4 D e ffo rd Jodrell Bank B irm in gham C rew e P ickm ere

D arnhall Data from the more distant telescopes (, D MERLIN currently MERLIN achieves coherence by the use of a

K no ckin ~100 km of new build (figure 3). The new build was e-MERLIN and new dig (the “last mile problem”) to the telesc Europe Limited [3], with the previously intalled fi intalled previously the [3], with Europe Limited

division division multplexed at Birmingham, resulting in 9 c way, apart from that for control and monitoring whi system. back back to JBO, thereby producing a go-and-return syst quality crystal oscillator at the telescope with a locked locked to Maserthe Hydrogen standard. Th frequency timescale variations in the path length are average superseded, and so we have investigated the use of 1.5 GHz) transmitted (via repeaters) to each telesc return signals is used on-line in the correlator to length changes in the reference link (anounting to day). This arrangement has worked very well, achiev of the free space system. A number of laboratory an illustrates the comparative behaviour of free space the using before correction even fibreof system a transfer system transfer system in light modulating on fibre instea PoS(EXPReS09)029 Ralph Ralph Spencer Graph showing the Graph showing go Figure 4 and return link phase (in turns at 1.5 GHz) using for the MERLIN free JBO to space system antenna (red), and based using JBO optical fibres (green), to over ~ 1 day. The two path lengths are within a factor of 2 simultaneously. and were measured out out to the JIVE correlator, which o VLBI has scientific benefit due to nternet nternet break-out boards (iBOB) [6]. ckages ckages in the EXPReS project were network testers, where high speed (10 the remote telescopes and up to 1024 ) to allow up to 4 telescopes at 1 Gbps ts ts at higher data rates than possible with isting isting analogue links are being used for community for several years. The use of ata ata from Onsala has been passed into the nect data from Onsala into the e-MERLIN s s been developed, though further tests are he he station isboard for designated providing short spacings. There has been consistent g g UDP packets and errors counted. Tests to ously at (see loss ously with 4 Gbps no talk packet ntil ntil after further e-MERLIN telescopes have ndwidth, presents an interfacing problem for signals can be routed either in or out to the VLBI VLBI in particular) has been achieved by the

5

Firmware Firmware for passing data from e-MERLIN telescopes The incorporation of multiple MERLIN telescopes int demand demand for this facility from the VLBI astronomical the new digital links, though enabling very high ba VLBI since data formats are very different. Work pa tncreased tncreased sensitivity and the addition of valuable designed to overcome this. The work packages were 1 the JIVE correlator. so A FPGA chip VSI called on t each to be connected to JIVE (in SA1) and 2) to con correlator at 4 Gbps (in FABRIC/JRA1), allowing tes a high data rate parallel digital interface – where use of the University of Berkeley’s CASPER groups i correlator. correlator. The interface to the IP network (for e- These FPGA boards have been also developed by us as Gbps) can be tested over a range of data rates usin obtained. spectra autocorrelation and correlator, Onsala Onsala that the have cancontinlink shown transmit by Richard Hughes-Jones at this conference). Test d 4.Connection of e-VLBI to e-MERLIN e-MERLIN rechannelises rechannelises and removes the delay corrections, ha needed. needed. We do not expect to get full connectivity u been brought into operation. In the meantime the ex eVLBI observations using data rates of 128 Mbps for Mbps for the local Mk2 or Lovell telescopes. telescopes. Lovell or Mk2 local theforMbps PoS(EXPReS09)029 Ralph Ralph Spencer , viewed 30/07/09 l 008 viewed 31/7/09 viewed 4/8/09 at JBO. Special thanks are due to e observations via the usual twice viewed 27/7/09 r r the Sixth Framework Programme, orrelator occured in early April 2009, viewed 30/07/09 d by external referees and a Legacy he whole process was an important . The breadth of the proposals clearly 31/7/09 viewed being obtained on April 13th. The first ussion ussion and provision of slides.EXPReS is projects. A call for large high scientific obtained on April 24th. Since then fringes ~50% of e-MERLIN time in the first 5 .html#program y y than that and for typical VLBI, MERLIN sts sts from 119 institutes, clearly indicating a hough hough further improvements to the K band re re expected to be delivered in the Autumn cientific output. cientific ng ng time was well with over-subscribed 5000 topics from the formation of planets to the , viewed 27/7/09. e further telescopes over the next few months, At the we moment have 4 station boards and 1

ray in early 2010. inray early 6 http://www.merlin.ac.uk/legacy/ http://www.globalcrossing.com/ http://www.e-merlin.ac.uk/ Precise Time and Time Interval meeting December 2 http://www.fujitsu.com/uk/news/pr/ftel_20090514.htm th https://mitr.drao.nrc.ca/widar/index.shtml http://casper.berkeley.edu/wiki/IBOB

Many Many thanks are due to the e-MERLIN and VLBI teams First light through digital lnks and the e-MERLIN c e-MERLIN e-MERLIN will be used both for standard rsponse mod Fujitsu Press Release e-MERLIN Legacy Projects web site CASPER web site e-MERLIN Web site WIDAR WIDAR correlator McCool, R., et al. 40 Global Crossing web site http://www.pttimeeting.org/archivemeetings/ptti2008

[3] [7] [6] [1] [2] [5] [4] Simon Simon Garrington and Rob Beswick, for valuable disc funded by the European Commission (DG-INFSO), unde #026642. Contract References References Acknowledgements Acknowledgements 6.Current Status and Future Plans and Future Status 6.Current e-MERLIN 5.The Programme Legacy formation formation of galaxies in the early universe. Around semesters will be allocated to the Legacy progammes hours allocated to 11 successful projects, covering demonstrates the versatility of e-MERLIN s interestand potential community of demonstration [7], and t Steering Steering Group, chaired by Prof. R. Ivison. Observi wide community interest. The proposals were reviewe resulted resulted in 15 proposals submitted from 325 scienti followed by an autocorrelation spectrum of fringes between the Mk2 and Tabley telescopes were 2009. All receiver font ends have been completed, t receiver are scheduled. It is planned to incorporat ar full the runs usin science test and initial with impact impact aimed projects, at reaching a communit wider have been stabilised, with correct tracking. delay baseline board. The rest of the correlator boards a yearly yearly proposal system and for large scale ‘Legacy’