PoS(10th EVN Symposium)011 els- ff http://pos.sissa.it/ ce. a 4-telescope array (E eview the proposals and the l European astronomy s 10th EVN Symposium. To- or Proposals was issued with a 20 telescopes at 18 locations in outine in both. Here I describe cording with a 2MHz bandwidth VLBI and the new generation of radio o formalize joint European VLBI ipate in e-VLBI observations with vities, the start of the EVN, and its ecording for 63 days a year, and an ed to EVN observations. A 16-station -53121 Bonn, Germany ive Commons Attribution-NonCommercial-ShareAlike Licen ∗ cial EVN observing session took place from 3–9 October, with ffi [email protected] Speaker. At a meeting in Bonn on 5th March 1980, the directors of severa institutes agreed on setting upactivities. the European A VLBI Program Network,deadline Committee t of was 15 established May. andfirst The a o committee Call met f in Onsala on 4th June to r berg, Westerbork, Jodrell-MKII and Onsala-25m) at 5GHz, re (4Mbps). Thus we celebrate the 30th birthday of the EVN at thi day the EVN comprises12 15 countries institutes, spanning which 4 continents operate andarray a a can total now correlator be dedicat of used atreal-time 5GHz correlation. and 11 The stations EVN regularly observes partic using disk-based r additional 10 days using e-VLBI; observations at 1Gbps are r some of the early history ofgrowth European in size astronomical and VLBI scope acti over the past three decades. ∗ Copyright owned by the author(s) under the terms of the Creat c

E-mail: R. W. Porcas Max-Planck-Institut für Radioastronomie, Auf dem Hügel, D A History of the EVN: 30 Years of Fringes arrays September 20-24, 2010 , UK 10th European VLBI Network Symposium and EVN Users Meeting: PoS(10th EVN Symposium)011 R. W. Porcas (NUG) was ber (Chilbolton). le-baseline VLBI n 1971 the Jodrell - Jodrell MKI and Onsala mber 1977. From left to right: rson, Winnberg, Robbins (Oxford), eria on 7 April 1975 [22] and led 76). The author’s VLBI initiation long, began in March 1976. Two 1). Network Users Group dard for global astronomical VLBI, bservatories continued observations wever, were in Canada and the USA obtained to Arecibo at 610 MHz in rferometry in Europe began as early NRAO MK II recording system with , 10.7, 5 and 1.6 GHz. Discussions on eduling for a network of 7 telescopes. ed in a number of places [4]–[12]. The n January 1968; Jodrell in June 1968; OH-line VLBI observation took place mea [1]–[3]. Construction of a system y the Jodrell Bank group n, Sykes (Nottingham), Porcas, Anderson, Wall motion in [15]), the benefits of using 2 superluminal Stannard, McSteele (NPL), Bååth, Preuss, Cohen, Booth, Bar elsberg and Onsala [21]. In the USA a Front: ). Despite some key astronomical results obtained from sing ff left Oct 1969) were with baselines to US or Canadian telescopes. I / produce the first VLBI fringes between 2 European telescopes 4th informal European VLBI Meeting, Jodrell Bank, 1st Septe did Ponsonby, Matheson (Chilbolton), Matveenko, Rönnäng, Pea Discussions on the feasibility of tape-recorded radio inte system [13][14] (Fig. 2 Back: Figure 1: 2 MHz bandwidth, introduced in 1971,and became remained a a universal workhorse stan for two decades.with In transatlantic Europe several partners o [19][20].in A successful 1975 1.7 between GHz E A History of the EVN 1. The emergence of VLBI activities in Europe arrays of many telescopes were soon apparent [16]-[18]. The as 1963, in the context of extendingbeyond the baselines those operated possible b with radio linksbegan - at in Jodrell particular around to 1967,November Cri 1969 and [1]. “fringes” The first were successful eventually VLBIin experiments, 1967, ho and the story of these developmentsfirst has VLBI been describ observations at European observatoriesSimeiz (Onsala in i Sep experiments (e.g. the 1971 discovery of Pauliny-Toth, Davies, McLintock (Nottingham), Kellerman (RGO), van Ardenne organized in 1975 [7], to coordinateA proposal regular review and series sch of 6observing observing frequencies were sessions observed per in each, year, chosensetting each from up 22 1 a week European VLBIto Network a started series in of the meetings MPIfR (Septemberwas cafet at 1975; the March 4th and meeting October at 19 Jodrell Bank in September 1977 (Fig. PoS(10th EVN Symposium)011 els- n at ff – with polariza- R. W. Porcas elsberg and every ing 100mas. ff ous one for radio interfer- escope” in 1987), together er 1976 [23], with observa- ator in Charlottesville. Euro- eeting of European Directors , Simeiz and Haystack [28]. [31][32], 1.6 GHz in February d by the large collecting areas ittee, and an agreement to have ed. Some results from the first proposal review and scheduling, PIfR correlator. Although some ator at the MPIfR was completed ) are mentioned in [34] and [35]. ry 1 minute at E de [27] while 22 GHz observations took place from 6–9 January 1978. om the founding of the EVN was a this was an attempt to do and the newly discovered first gravi- he single-channel MK II system, was left elsberg, Onsala and Dwingeloo (Fig. 2 ately published [25][26]. March 1978 opes in NUG sessions, notably E e Heidelberg VLBI Symposium in Au- ad hoc result in immediate publications on two ff k operation. an VLBI results from both before and af- did 3 – a plan to coordinate proposal review and scheduling Jodrell–Onsala fringe visibility at 1.67GHz on 3C345 from Left: Fronhof Europe-only VLBI sessions were organized in March (Eb, Wb & O 3–station run, October 1976 – 3C236 at 1.6GHz [23]; tick spac ad hoc 561A,B [30]. At a VLBI Workshop held on 7-8th November in Bonn + Right: First all-European VLBI runs. elsberg and the Jodrell MK IA telescope (renamed “Lovell Tel ). These observations were processed at the NRAO MK II correl VLBI at 1.6 GHz, taking advantage of the sensitivity provide This decade leading up to the formation of the EVN was a moment In 1979 further The first 3-station “Europe only” VLBI took place on 2nd Octob ff berg, which had become anon associate 5th March member 1980 in finally 1979. led6 to EVN The the observing first setting up sessions m of persession a year. program in comm The October EVN 1980 wasInterestingly, (see both thus observing publications establish schedule present in seriester of Fig. Europe that 3 session; tostreamlined some administration extent of the an main already-existing networ immediate result fr 1971.2 [13][14]. 5 GHz) and June (Eb, Jbof & the Dw “hottest” at astronomical 1.6 GHz) objectstational and of these lens the 0957 day, SS433 [29] lunch at the author’s favourite pub Figure 2: A History of the EVN tions of the giant radio-galaxy 3Cright 236 at 1.6 GHz, using E pean VLBI received a boost whenat construction the of end a of MK 1977. II ANamed correl second, “JODE” ambitious, European (after experiment thetion initial letters of the telescopes), in Europe was discussed. Europe-only sessions, still with of E continued into the first[33]), half alongside of the 1980 participation (5 GHz of in some European January telesc and June 2 minutes at Jodrell.preliminary This polarization experiment VLBI was results the weregust presented first at 1978 to th [24], use only the single M saw the polarization first results use were of Westerbork ultim were (at 1.4 made GHz) in in November phased-array 1977 mo and October 1978 at Ef, Onsala-20m with Onsala and Dwingeloo. Cross-handachieved correlation, by switching using between t LHC and RHC polarizations eve PoS(10th EVN Symposium)011 elsberg, ff orator), fol- R. W. Porcas absentee ob- he PC Chair’s 0 MHz was added in 1983), ERLIN (1980). (The dedica- s ever since) following Calls eir common frequencies; hence .) It saw the introduction of the not only reviewed proposals but Network, thus facilitating VLBI erferometry results. on. The EVN Program Commit- ons, each up to 1 week long, were " tapewidths, resp.) on the shelves. Bonn MKII correlator, 1980. Note the nd Scheduler roles were completely 1 2 scientist. It provided more recent Scheduler’s year). ] and its incorporation into synthesis scope was to start operating 4 years ambridge 5 km telescope (1971), and committed observatories (E sive tool of the Cambridge 1 mile tele- es from each network were proposed, otably Simeiz, Hartebeesthoek and the es. Many proposers saw the advantage esolution, compared with the US Net- nd operational aspects of the observing Right: From its beginning the EVN operated an ly) was the norm for other interferometers; 4 making service observations in the absence of a local collab elsberg scheduler was appointed Scheduler, to coordinate t ff ff First EVN Session schedule, October 1980. Left: (observatory sta Proposals, Observing Sessions and Telescopes: The basic 4-telescope EVN operated at 1.4, 1.6 and 5.0 GHz (61 sessions. In 1982 the E lowing the earlier introductionfor of astronomers this who idea were in nottee 1979 (EVNPC) part on initially of comprised the a 5 US largeWesterbork, representatives Jodrell, VLBI from Onsala collaborati the and Bolognalater - - the and Medicina 3 tele for “non-VLB” Proposals members. on 1st It of met February,also, June 3 via and times its October. observatory each The members, year EVNPC coordinated (it technical ha a 3 generations of MKII recorders (Ampex, IVC, VCR with 2", 1" & Figure 3: A History of the EVN serving “open skies” policy, accepting proposals from any qualified ometry, with the construction of Westerbork (1970)the and start the up C of the UStion VLBI of Network the (1976), VLA the took VLACLEAN place (1979) algorithm on [36], and closure-phase the M in day the after VLBIimaging context the [38]. [37 first Prior to EVN 1970, session synthesisscope, imaging and was model-fitting the visibilities exclu (often amplitudes on by 1980 imaging had become the expected way of presenting int 2. EVN – The First Ten Years 1980–1990 plans for the sessions with the NUGseparated schedules. from (The 1990 PC Chair on; a see [39] for the author’s account of a providing an array with highwork. Other sensitivity, telescopes albeit were moderate frequently added r Torun-15m, to organized the separately array, by n the proposersof themselv combining the EVN and“Global” the experiments US were Network recognized for if observationsand at at reviewed th least by 2 both. telescop A total of 6 single-frequency EVN sessi PoS(10th EVN Symposium)011 1 liate (as 70m) 1983; (f) Wb [50] ffi > A R. W. Porcas MERLIN telescope = ries 8.4 GHz frequency / rr. (F) ][44] 1985(a)lapsed erent telescope; M [45][46] 2001A [59][60] 1985(a)lapsed ff rom November 1988 (the z [68] (F) lescope took place in Decem- able (e.g. Onsala 20m and Ef- eodetic 2.3 the decade over 75% of EVN 8.4GHz M.Kharinov 2009F 8.4GHz M.Kharinov 2009F 8.4GHz QianZhihan 1994F 8.4GHz [66] 2009F 8.4GHz [62] - 8.4GHz [64] - 8.4GHz [49] 1997a UENCY REFERENCES EVN CONSORTIUM / / / / / / / mbridge 1mile telescopes and the als at the NUG frequencies of 22 2.3 2.3 ved, operating 4 sessions per year after 1990). Other new telescopes ervations at 10.7 and 22 GHz, and, that frequency; in 1982 this was re- 1986 the US Network also dropped an participating at 22 GHz in 1986. pes took part in 4 Global observations institute now F with di able VLBI observations) at EVN and = nstitute joined the EVN Consortium. side the remit of the EVNPC. However, in particular Medicina in 1984 and Noto ) 2.3 Kauai 8.4GHz QianZhihan 1990(a),1994F + DSS13 2.3GHz [22][48] 1984F Haystack 5&1.6GHz [41][42] 1984F Haystack 8GHz [51] 1984F + + + MERLIN observations, with VLBI recording + VLA 1.6GHz [65] M Penticton 408MHz [1][43] 1984F Onsala-20m 43.0GHz [63] 1994(a),2000(f)Ys-40m Medicina 10.7GHz [61] (F) Onsala-26m 1.7GHz [23] EVN- othersothersWesterbork 5.0GHz 5.0GHz 5.0GHz [53] [31] [53] - M 1990A no longer A; (f) + Gilcreek + + + + + + + = Zelenchukskaya 2.3 others 2.3 + 5 + + + elsberg elsberg elsberg elsberg elsberg elsberg elsbergelsberg 5.0GHz 1.4GHz [54] [55] 1985(a)(f)Tr-32m (f)Seshan elsberg 1.4GHz [27] 1984F ff ff ff ff ff ff ff ff ff ). left operating institute already F; (a) = ord. Simultaneous EVN ff First VLBI Observations at EVN and other European Observato Associate; (F) = Full; A = Table 1: ord and Cambridge, became a regular feature of EVN sessions f ff A successful 327 MHz VLBI experiment with the Ooty (India) te MEMBERSHIP: F 1 20042005 Nov4 DARNHALL BADARY 1980 EVN 2005 Svetloe 6.7GHz [67] M 2008 May30 YEBES-40m 2007 EVN(datatransferviaFTP) 22.0GH 1994 Sep14 NY-ÅLESUND 1994 2003 ZELENCHUKSKAYA 2000 Svetloe 2.3 19961999 Apr17 Nov16 TORUN-32m TABLEY(Pickmere) 1980 1995 Westerbork Medicina 5.0GHz A.Kusetal. 1998F 2003 Mar6 SVETLOE 1998 IVS 2.3 1990 Nov17 CAMBRIDGE-32m 1990 Jodrell-MKII 5.0GHz Bonn-co 19901994 Jun25-26 Mar16 YEBES-14m NANSHAN(Urumqi) 1976 1994 E Seshan 1990 May 24 MATERA 1990 Wettzell 1989 Mar NOTO 1988 E 1973 Nov20 ROBLEDO-64m(DSS63) 1973 Hartebeesthoek(DSS51 196919701972 Sep–Oct1973 Nov7 Nov Jun18–21 SIMEIZ HARTEBEESTHOEK EFFELSBERG CHILBOLTON 1961 IslandLagoon(DSS41) 1966 1971 1967 GreenBank-140ft GreenBank-140ft Algonquin 2.3GHz 5&10.7GHz [2][12 10.7GHz [47] - 1976 Oct2 DWINGELOO 1956 E 1968 Jun27–29 JODRELLMKI 1957 Algonquin 197919801981 Mar1981 Jun1–21983 May31 Nov12 Jul27 METSÄHOVI KNOCKIN TORUN-15m SHANGHAI-6m WETTZELL 1974 1976 1976 1981 E E E E 1983 Onsala-20m 8.4GHz Bonn-corr. 1985 198419841984 Mar1984 Jun51987 Jun5 Jun June9 MEDICINA DEFFORD CAMBRIDGE-1mile NANÇAY SESHAN(Shanghai) 1964 1983 1987 1961 EVN EVN Kashima EVN 1965 1.6GHz 5.0GHz [57][58] 1.6GHz [56] [57][58] M M 1984F 19781978 May Nov JODRELL-MKII CAMBRIDGE-5km 1964 1971 Onsala-26m E 1.7GHz [52] 1984F 1978 Mar31–Apr2 WSRT-phased-array 1970 E YEAR1967 DATE OF OBS.1968 Aug TELESCOPE Jan27–Feb3 ONSALA-26m ARECIBO BUILT PARTNER TELESCOPE(S) 1964 FREQ GreenBank-140ft 1963 GreenBank-140ft 610MHz [40] 2001A 1977 Sep21–24 ONSALA-20m 1976 GreenBank-140ft at De new Cambridge 32m telescope replacingbuilt the specifically for 1-mile VLBI telescope started full network operation, other European telescopes, and the year the corresponding i in 1989. Table 1 gives the dates of first fringes (or first trace duced to 4 per year. In Juneat 1984 1.6 a GHz record-breaking [57][58], 18 which telesco saw the firstMERLIN VLBI telescope use at of one De of the Ca A History of the EVN organized in 1981, preceding or following the NUG session at pair as standards inproposals 1987 were Global and (see 1988 Fig. 4 respectively. By the end of ber 1983 [69][70], involving several EVN telescopes butthe out category of Global wasand expanded 10.7 in GHz 1984 and 327 to MHz includefelsberg if at propos at 22 least GHz). 2 The EVN newfollowing telescopes telescope a were in surface avail Medicina upgrade, joined obs theThus Jodrell EVN operations MK II grew telescope intoto beg multi-frequency 4 sessions. sessions In per year,at and up gradually to a 3 frequencies Global in VLBI each. array The evol EVN adopted 8.4 GHz and the g PoS(10th EVN Symposium)011 r -

).

2009 996

2008

2007

right 2006

MK2 MK3 MK4 2005

2004

R. W. Porcas 2003

2002

2001

2000

1999

1998

1997 t increase in MK III *1996

tion changed with the

Recording systems used

1995 1994

0”) for continuum obser- 1993

minals and tapes (see [72] 1992

width and thus limited sen-

1991 Right:

1990

1989 capacity and 5 playback drives

ecording took place in October 1988

K III recording (see Fig. 4 th a first meeting in Bonn on 8-10 1987 d the gradual acquisition of termi- station “Block II” correlator [71]. acks recorded on a tape. In 1990

number of large Global continuum 1986 ecording for all but the most worthy l Working Group (TWG) - renamed

jects were observed using the MK III 1985

sity Upgrade project at the end of the Global projects involving US collab- 1984 small, local or spectral-line projects.

$400) per tape and their short running stem, developed primarily for geodetic elsberg azimuth track.)

) being the default processor for Euro- 1983 d as such). ff ∼

ourse, necessary for obtaining data from

1982 istance was given to visiting astronomers 1981

og of EVN observations, supplemented by the eE *1980 right 0 90 80 70 60 50 40 30 20 10

6

2009

2008 ered a dramatic improvement in bandwidth (56 MHz

2007 ff

2006 2005

Numbers of Proposals. (* only 2 deadlines in 1980; this numbe 2004

projects observed 1997-2001. (* only 2 sessions in 1980; in 1

2003 2002

Initially the common recording system for all EVN observato 2001 Left:

2000

1999 VSOP

1998

1997

1996

1995

1994

1993

1992

1991

1990

1989

1988

1987 elsberg and Onsala, with correlation at Haystack. The situa

1986 ). These developments, known as “MK IIIa”, resulted in a grea

ff

1985

. However, Caltech operated a 5-station correlator (“Block 1984

left ff 1983 2 MHz channels), albeit with much greater costs of record ter

EVN Statistics 1980–2009: 1982

×

e-vlbi *1981

Global *1980 EVN-only The single-channel MK II recording system had only 2 MHz band Recording and Correlating: 0 20 80 60 40 100 120 observing time. By 1990 over a third of all EVN projects used M time (13 mins at 56 MHz) initiallyprojects prevented the (Fig. use 5). of The MK III situation r wasdecade, eased which with the provided Track a Den 12-folda new increase MK in III the correlator number(see was Fig. completed of 7 in tr Bonn, with double the for a review of VLBI instrumentation). Someterminals early at Global E pro completion of a MK III correlatornals in at Bonn other at EVN the observatories. end At ofTechnical this 1982, and time an Operations an Group EVN (TOG) Technica in 1998February - was 1983. formed, wi The first1983, EVN-only with user correlation in projects Bonn. using MK However, III the r high cost ( Figure 4: is also a lower limit. In 1981 some Globals may not be classifie A History of the EVN with 28 vations, and this was usedorators. for some By experiments, especially 1988 CaltechThis became had the finished MK construction II correlatorexperiments, of the of the Bonn choice 16- correlator for being the reserved increasing mainly for sitivity for continuum observations. The 28-trackVLBI, MK III had sy been introduced in 1979, and o pean investigators; multiple correlation passesall were, baselines. of “Absentee c correlation” did notby exist MPI but sta ass in observations, compiled from entriesauthor’s records. in Numbers the exclude Bologna catal ries was MK II, the 3-station Bonn correlator (Fig. 3 observations were severely reduced due to replacement of th PoS(10th EVN Symposium)011 × R. W. Porcas ch panel is 60 of the EC’s Com- 87; 6 epochs, spaced by 2 DGXII which could be “referred see Fig. 6). (Meetings were Like its US counterpart, the ectors decided to formally es- European Communities” (EC) relator, to match future growth 7 [75][76] leading eventually to eration from its own funds. Fol- drive at the Bonn correlator with rade. The main proposal proved roach to ttzell. An obvious “outside body” ortance and value of this project”. year), with Associate Membership e proposal to the EC for funding a t from editorials [77][78] – nt was signed in July 1984, and the e, wideband correlator with a capac- m-up” structure, with each member stitutes met annually (twice in 1983). Global 9–station 1.6GHz observation of s successful and was used to support ere Onsala, NFRA, MPIfR, Jodrell and VLBA recorder by a European company, / Right: 7 was prepared, along with one for a “Twinning Grant” 561 [74] in November 1989; image B on left, image A on right. Ea + EVN 5–station 5GHz observations of SS433 [73] in May-June 19 Consortium of European Institutes for VLBI Advanced Data Processing Facility Left: The EVN Consortium and Search for European Funding: to in approaches to outside bodies”.first The EVN Consortium Consortium Agreeme meeting heldheld subsequently on twice 12 per year.) February Full 1985 MemberIRA-Bologna institutes in (each w committing Bonn at ( leastfor 45 Torun, days Simeiz, observing Nançay per and theto new approach geodesy telescope was in the We Europeanand Economic becoming Community the (one European Union of (EU) the in “ 1993). An earlier app EVN had started asobservatory an providing admirable, manpower astronomer-driven, and “botto equipmentlowing for their the first EVN meeting in op 1980, theOne directors central of theme the of EVN discussions in becameity the funding beyond of that a of larg anyof planned the expansion EVN. of In the thethe Bonn USA VLBA. similar MK At III plans their cor meeting had in startedtablish Vienna as the on early 16 as June 1984 197 the EVN dir 120mas. Note the opposite image parities. Figure 5: A History of the EVN days and consuming most of the EVN MKIII tape supply! 0957 mission in September 1983 had20-station been unfruitful. In 1986 a larg an engineer in Bonn andto travel be associated too with large for thealthough any MK in IIIa identifiable 1989 upg EC some budget money – wasThis granted despite was to used suppor “highlight to the fund development imp of a prototype MK III improved electronics. (submitted October 1986) for interim support. The latter wa Thorn-EMI (later Penny and Giles), and a 6th MK IIIa playback PoS(10th EVN Symposium)011 ). left cially ffi R. W. Porcas Schilizzi, van der ium (as it had o MK III observations almost Clockwise: he same basic tape transport, lator could process them but, N for Global experiments. The ped with MK II recorders; the ged when, as a result of the US annels. The 10 new telescopes ccess to the VLBA correlator). he EVN). e Town was the first in 1987) it st in time for compatibility with h VLBA modes and a formatter tor capable of processing Global uary 1993. EVN and Global MK II nd operated alongside the new, to- gth “thin” tapes. After the decline rades, the first being a modification etwork telescopes were replaced by the plan was the network frequency sals from 1994 on (see Fig. 4 sed at the Block II correlator. (The oring programs; the last Global MK II th support from the German geodesy uding the Penny and Giles prototype). tveenko, Booth, Pauliny-Toth, Graham, Mezger, The US (VLBA) came 8 . VSOP First meeting of the EVN Consortium, Bonn, 12 February 1985. The loss of MK II and limited access to the VLBA correlator for NRAO took over US Network operations from the US VLBI Consort Impact of the VLBA and EVN expansion: Figure 6: A History of the EVN certainly contributed to the drop in numbers of Global propo was added into US Networkresulting sessions. enlarged Global The experiments firstBonn could seven MK II only were correlator be equip was shut proces Transition down Plan, on the 15 NSF June ceased 1992.) to Thisoperations fund ceased chan VLBI almost at immediately Caltech except in for Jan aproject few was monit observed in September 1994.of Another 10.7 GHz casualty (last of Global session inthose 1991), of as the the VLBA, original which US had N 15 GHz instead (never adopted by t into being gradually [79]. When each new dish came on line (Pi 3. EVN 1991–2000 Laan, Brouw, Seeger, Smith, Gorgolewski, Setti (Chair),Wielebinski, Ma Zinz, Porcas, Schwartz. become in 1981) on 1 JuneVLBA 1992, recording and system became had the much partner in ofbut the common employed EV with new MK recording IIIa, modes usingcould with t record wider some and fewer MK IIIa “IF”for modes ch operational and reasons, the the VLBA 20-stationof had VLBA MK II to corre in use 1993 new, the double-len observations VLBA with correlator large was numbers the only ofcommunity, large telescopes the correla although, original Bonn wi MK IIIgether with correlator an was additional revived 3 a Thus playback EVN drives observatories (10 embarked in on total a seriesof incl of the recording upg MK IIIa recordersA to further permit upgrade use to of MKcapable IV thin of (wideband recording tape channels up (and compatible to hencethe wit 1 Japanese Gbps) a Space was VLBI implemented project, by 1997, ju PoS(10th EVN Symposium)011 ncy R. W. Porcas program for VN observations as also reached with JPL, y inaugurated on 22 October frequencies were also added orun-32m telescope brought hai) telescope joining in 1990 I institutes (or, later, their fund- servatory directors, JIVE’s main ith the VLBA in February 1995 vatories. nes) in May 1995. e) would provide 16 h of observ- EVN telescopes. EC funds were EVN-only proposals, perhaps be- d Bonn correlators to oversee cor- th June), largely with 5.5 M ECU Hartebeesthoek became Associate Joint Institute for VLBI in Europe tes, including truly intercontinental ; by 2000 it was processing all but a th contributions from other sources. elator and provision of user support l, some funds were used to pay EVN was observed in June 2000 and sent to Global projects (shared with the VLBA n the Province of Drenthe, loads a tape on ted in a change of tactic in 1992. Stim- Inauguration of the EVN correlator at JIVE, rd Schilizzi, Director of JIVE. Human Capital and Mobility Right: 9 The failure of the EC to provide the 17.8 M ECU (European curre ); first fringes had been obtained in July 1997 [81]. The first E right Bonn MKIII correlator upgrade 1990. Left: The new 16-station EVN MK IV correlator at JIVE [80] was finall The Founding of JIVE: destined for the EVN correlator atsmall JIVE fraction were of observed EVN-only in projects, 1999 and roughlycorrelator) half shortly of all thereafter. The last EVN MK III project one of the Penny and Giles playback drives, assisted by Richa October 1998. Mr. Relus ter Beek, the Queen’s Commissioner i 1998 (see Fig. 7 Figure 7: unit, roughly 1.2 US $) toulated construct by a an large award correlator of resul “Access 1 to M ECU Large from Scale the Facilities”,(JIVE) EC a - under new its was EVN established institute infrom - the Dwingeloo the Dutch in Ministry of 1993 EducationWith (inaugurated and its Science, 9 own Director but and also a wi governing Boardpurposes composed were of EVN the ob construction andfor the operation EVN. of Operations a costs large wereing provided corr agencies). by a Before number the of newSupport VLB correlator Scientists, two became of operationa whom wererelation stationed of at EVN the VLBA projects; an othersalso were used to employed finance at three some “EVN of Research the Fellows” at EVN obser cause the EVN hadand expanded Nanshan eastwards, (Urumqi) with in the 1994.to Seshan 9 By the (Shang number 1996 of thebaselines. telescopes addition operated (Two of more by continents the Full were Member new addedMembers institu T when Arecibo in and 2001.)whereby Between the 1997 DSN 70m and dish 1999 ating a Robledo time (and working for also each agreement that EVN at w sessionto Goldston if the recommended EVN by the repertoire, EVNPC. withand New an a EVN–only 43 6 GHz GHz Global session session (for methanol together and w excited-OH li A History of the EVN Remarkably, this drop was accompanied by a sharp increase in PoS(10th EVN Symposium)011 in on id not VSOP R. W. Porcas ord Arms ff of JIVE organized rbiting the Earth is ff De Tra Castel S. Pietro Terme Scientific Review Com- ; there was a special meeting 30% of its observing time to VSOP meetings.html) / twork for astronomy. Terme, reviewing VLBI “in the 94 in Torun, and they have been lace in the rease the time between proposal 1995 the sta 1993 but, to accommodate vations. of ground telescope time for this tersburg, increasing the availabil- w-bound !) EVNPC ratings were 1993 on user feedback led to the Thus the first “EVN Symposium” es and practical demonstrations of km and a perigee height of 560 km November 1999. A further school VSOP elescope (2003), the completion of f the ays, with up to 3 observing frequen- ere heavily involved in two proposed ied by users meetings. (Proceedings VLBI Space Observatory Programme Bologna in June 1983 and Manchester come increases in EVN collecting area . onal phase of the mission (1997–2001), meetings s, too, was shut down and resurrected as / (1990)[86], but neither came to fruition. The first EVN Users Meetings took place on IVS 10 took place on 20 November 2001 and from that year on www.evlbi.org // following its successful launch on 12 February 1997, de- observations were run in MK IV recording mode “128-2-2” VSOP (1982–88)[85] and HALCA VSOP JIVE Mini-Symposium and Users Meeting” to be held at Jodrell / frequencies of 1.6 and 5 GHz being run in each session (22 GHz d QUASAT VSOP The idea of performing VLBI together with a o . The satellite, renamed . The EVNPC reviewed all proposals for open-time with The first VLBI School was organized by the EVNPC and was held in The last EVN observation with VSOP: EVN Users Meetings, Symposia and Schools: Alderley Edge since the plannedcommunicated venue to of the Jodrell mission via Bank its was Chairman’s membership sno o mittee. The number of EVN sessions perobservations, year the had EVN dropped increased to this 3 to in 4with during the the functioning operati the number of sessions per year reverted to three, each of 21 d cies. From May 2003submission this and was observation increased for to less-used 4came frequencies. frequencies in Wel to this decade dec withthe a new resurfaced, Yebes 40m 5 GHz-capable telescope Lovell and T theity accession of of the the three IAA 32m St. telescopes Pe of the KVAZAR geodetic VLBI ne (near Bologna) from 12–23 September 1988 [82]. In September survive the launch). All EVN and correlated at the VLBA correlator. 4. EVN 2001–present to review the first 150 proposals on 27 January 1996. (It took p a 3–day VLBI School in Dwingeloo,data which analysis. included both Similar lectur schoolswas were held held from in October 17–29 1997 Septemberlight and 2001, of the again most in advanced astronomical Castel observations” S. [83] Pietro almost as old as VLBI itselfspace-VLBI [3][84]. European projects, astronomers w ployed an 8 m dish, and orbited with an apogee height of 21,000 [87]. The EVN was atmission the via forefront the in Global arranging VLBIVSOP committments Working Group; the EVN committed the occasions of the international VLBIin conferences held July in 1992. Discussionssuggestion in of the a Consortium 1–day Meeting “EVN in April the occasion of the nextwas Consortium held meeting on in 22 October October. 1993. Theheld second every followed 2 on years 21st since Octoberfor 19 (with all increasing but the length), first accompan can be found at: http: A History of the EVN the Bonn correlator for processing.a Shortly MK afterwards IV thi correlator, primarily for geodetic and 3 mm VLBI obser A Japanese space-VLBI project was proposed in 1987 - the (VSOP) PoS(10th EVN Symposium)011 pean study R. W. Porcas , the transfer of VLBI I Call for Proposals was mission, showed it would be ustained operation. A move e–VLBI Wb telescopes and the MK IV s in “Mode A” (224 Mbps was rate was 512 Mbps; by January hout computers but organizing Today, computers, digital elec- nd using 32 Mbps transmission K IV recorders, 512 Mbps being 16–17 March with 6 telescopes at N observatories were using MK V, king part. ing runs 2 or 3 weeks later, before BA correlator. Shortly afterwards essions in June 2007. By the time L-SAT 003. However, 512 Mbps operation um recordable bit rate – had hardly he EVN); in 2001 using MK IV the tape drives with MK V disk recording itted an increase to 1024 Mbps, with a a little nostalgia for earlier VLBI times A’s ts use for real-time correlation eliminates First EVN e-VLBI image, 28 April 2004 Despite many technical advances in the first Right: 11 was first demonstrated in 1976 between Green Bank and ). left satellite for data transfer [88]. However, a very early Euro Real-time VLBI Hermes Disposal of old tapes, Bonn 2008 Left: ). After 2 further demonstration runs [90][91], a first e–VLB right elsberg telescope was connected in May 2008 the standard bit ff Another very significant development in this decade has been Concluding Remarks – Computers, Internet and VLBI: Higher bit-rates, Disk Recording and e–VLBI: Figure 8: far too costly. The firstcorrelator EVN at e–VLBI image, JIVE, using was the(Fig. obtained On, 8 on Jb 28 and April 2004, at 5.0 GHz a data from telescope to correlator overthe optical fibre need links; for i recording. Algonquin using the announced, with deadline 1 March 2006128 and Mbps. first 24-hour There run were on 9 speciale–VLBI e–VLBI deadlines deadlines, were with incorporated observ withthe those E for the main s of satellite-linked VLBI [89] in the late 1970’s, based on ES 2010 this had risen to 1024 Mbps at most of the 10tronics telescopes and ta the internet pervade our liveswhen so this I conclude was with not so. Of course, VLBI would not be possible wit A History of the EVN 20 years of EVN operation, onechanged. critical parameter From – 1980 the MK maxim IIIpossible was with regularly double used tape to speed recordEVN but 112 Mbp only was very still rarely limited used toto on 256 Mbps, t higher and bit-rates the began VLBAachieved to by for 128 using an Mbps EVN the for user observation s second forwith the record first tapes head time proved in unreliable of May and 2 M thewas gradual the replacement key of to making higherfirst bit-rates EVN possible. user observation It in also October perm 2004.with By June only 2005 occasional all EV use oftapes were tapes abandoned for (see projects Fig. going 8 to the VL PoS(10th EVN Symposium)011 , ff lopment of R. W. Porcas Latex cover-sheet / VLBI on this definition, sed for the first transatlantic not ty, but for 40 years the term curious is that VLBI imaging een built. There are so many ial growth of digital electronics ions is s, telescope and correlator sta p into AIPS th software running on computer corded signals, regardless of base- hat ool ed but a value of 18 months gives a and problematic characteristics. te back 30 years. Computer speeds line is isk”), with Tex or via 9-track magnetic “preptapes” elators at Bonn, Caltech, NRAO and were a million times slower. een Bank 140ft MK II schedules ing MK III observations ics ? A definition based on the use of es; are the long baselines of LOFAR al ASTBO1 server in Bologna m EVN correlator at JIVE 2] ugh post for MK III observations ssed with software correlators at both n the text. I thank Alan Dodson, John nition where the baselines are very long f some of the memorable steps forward. y done using telex and pieces of paper. uced at Bonn correlators [93] solve all the good amplitude calibration on and filtering, and they will soon replace 12 The Advance of Computers and the Internet in the VLBI Process in the lifetime of the EVN. This has now made possible the deve 6 Table 2: 19791980 Computer-readable punch cards1982 sent through post Computer-generated for schedules Gr on floppy-disk sent thro EVN120 data transfer format defined by EVN software grou YEAR1978 Input parameters and output data for Bonn MK II correlat 1983 Global HOWTHINGSWEREDONETHEN fringe search algorithm introduced into AIPS [9 19861988 Simple antenna-based fringe-fitting algorithm introd MK II SCHED program re-vamped to schedule VLBA observat 1989 User-friendly PC-SCHED program1993 available for schedul 1994 MK3IN provides robust route from Bonn First MK email III submission correlator of EVN proposals (“test – at own r 1992 Machine-readable schedules deposited via FTP on centr 20062007 First EVN e–VLBI observing run First use of the NorthStar EVN web proposal submission t 2004 Web access to archive of FITS files of visibility data fro Optical fibre connections have now made realtime VLBI a reali The term “Moore’s Law” is widely used to express the exponent I wish to acknowledge the hundreds of individuals – director Haystack. Table 2 records the author’s personal selection o A History of the EVN and controlling observations, particular MKLocal II, scheduling was and largel analysis programs grew around the corr VLBI has been synonymous withline radio length. interferometry What using can re we now“independent say clocks” are can its easily defining characterist getVLBI bogged ? down Certainly in the subtleti phase-locked Jodrell to Cambridge base and computing power with time.growth The factor doubling over time 10 is ill-defin even if correlated at JIVE. Perhaps simply revertingis to most a defi fitting; it is,sources after which is all, responsible the for fact one that of they VLBI’s most heavily enduring re today is still based on algorithms developed when computers 5. Acknowledgements and users – on whosethat I shoulders deliberately the chose EVN not and to its single-out any operation for have mention b i completely digital backends, using digital down-conversi are now such thatclusters; hardware EVN correlators observations are have beingBonn recently and been replaced JIVE. proce But wi this isVLBI not experiment new to Onsala – was the also 360 correlated kHz in MK I software ! system W [10] u their analog equivalents at EVN telescopes, some of which da PoS(10th EVN Symposium)011 R. W. Porcas bell, Paco Colomer, , ed. Finley & Goss (NRAO) p173 , ed. Finley & Goss (NRAO) p184 , ed. Zensus & Pearson (CUP) p1 María Rioja, Ute Runkel, Richard ve this talk, and the Editor of these A 39, 457 , 527 drzej Kus, Andrzej Marecki, George and completion date of this text. g. 1, Huib van Langevelde for provid- ading of the text. Finally, I thank the SP Conf. Ser. 144, p1 : MPIfR), p1 hen, M. 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