Jodrell Bank Observatory: Lovell Telescope, Goostrey, Cheshire East

Summary

Radio telescope of 1952-57 by engineers Husband and Company of Sheffield, to the requirements of Sir Bernard Lovell, with alterations of 1967-71, 2001-02 and the early C21.

Description

Radio telescope built from 1952-57, by Sir Charles Husband for Sir Bernard Lovell, altered 1967-71, 1976 and in the C21.

MATERIALS: steel.

PLAN: a circular paraboloid dish set within a cylindrical framework which is mounted on bearings at the top of two triangular legs, running on two concentric tracks of double rails with an overall diameter of 107m, supported by a concrete bed of the same diameter. In the centre of the bed is an annular chamber beneath the main pivot, with a tunnel to the south-east linking the dish to its control room. A smaller double-rail track surrounds the central pivot.

EXTERIOR: standing in former farmland with numerous research and support buildings, mainly to the east and south.

The receiving surface comprises a circular paraboloid dish of welded steel plates, 250ft in diameter. An extended central lattice mast supports the interchangeable receiver*, which is located forward of the plane of the front of the dish. Diametrically opposed towers 56m tall stand either side of the dish, known as red and green towers. There are five floors of rooms at the top of green tower (to the right on the day of inspection), clad in corrugated steel and with windows to each floor, while red tower has three storeys only, also with windows. On the inner face of these covered structures can be seen the edge of the circular trunnion bearings which transfer the load from the cylindrical support, to the towers. The towers have a central splayed space-frame, with an open central lift-core and stair. Two steel beams connected by cross-members form a forward-projecting raking support, with a four-wheeled bogey at the base of each member, running on an inner and an outer track. The tracks are double rails, bolted to the concrete bed. The towers are linked at the base by a lattice diametral girder, with raking braces running down to this. To the right, on the upper members of this girder stands a rectangular emergency generator house known as the Marconi Hut, of corrugated steel with two multi-paned windows, accessed by stairs. Within the centre of the girder, above the central pivot stands an equipment house of corrugated steel with two tall multi-paned windows. In front of the girder at this point is a frame of c1971 with two main legs visible with linking supports, mounted on two four-wheeled bogeys. Running along the top of the left and right side of this frame are two curved support girders which project forward to connect with the perimeter of the dish. A floating metal stair gives access from the ground.

Viewed from the left, red tower has a large projecting jib at its top, one multi-paned window in its metal-clad upper storeys, and splayed legs to its central structure, with linking supports, and a bogey at the base of each of the two visible legs, each with an attached drive motor. Between these two central legs can be seen the end structure of the diametral girder which links the two towers, and behind the tower the central structure can be seen including the left two legs and side of the c1971 frame on which are mounted the semi-circular support girders. From the base of the covered upper portion of the tower, two further legs rake to the left and right. These extend wider than the bowl itself, so that the overall length of the lattice girder which links them at the base is just greater than 250ft. The outer bogey can be seen at the base of each of these raking legs. The ‘red-side’ semi-circular girder can be seen to the left and right of the tower structure, together with the ‘starburst’ support structure which links the semi-circular girder to the base of the cylindrical space-frame to the left/rear of the dish. To the right of the tower, the rear structure and rear face of the original receiving surface can be seen between the members of the cylindrical support frame, and the receiver projects beyond the plane of the dish aperture. At the perimeter, a substantial rim* covers the gap between the current receiving surface and the original. Just visible to either side of the upper structure of the tower is the outer perimeter of the trunnion bearing.

From the rear the towers, diametral girder and central support frame have the same appearance as from the front. If the dish were elevated to the zenith then this would also have the same appearance, but at the time of inspection, with the dish depressed, the underside of the cylindrical space-frame was visible, with radial spokes linked laterally to create a series of concentric rings. The semi-circular support girders were also visible, linked by cross-member arrangements resembling the union flag. To the left, a metal stair runs from ‘green’ tower towards the nadir of the dish, accessing the swinging laboratory. The swinging laboratory was at the time of inspection removed for maintenance, but located adjacent to the dish. This comprised a small rectangular corrugated-steel cabin with pitched roof. Each long side has a central nine-paned window, while each end has a circular pivot. The ‘green’ end has a small enclosed landing where the access stair would meet it, and a door. The annular chamber is entered via steps in the concrete bed, to the north of the central pivot.

Viewing the dish from the right, the green tower has the same appearance as the red tower does from the left, but with an additional two covered-storeys below the junction of the raking legs with the splayed legs.

INTERIOR: within the upper levels of the towers the steel frame is exposed but the corrugated cladding is sheet-lined. Metal windows, light fittings, etc are all original. The upper levels contain the motors and gearing of the elevation drive which moves the dish via the former battleship gun-turret racks. The top floor has a very large block and tackle and houses the trunnion bearings, connected to the frame of the dish by steel cones. The lifts* of the towers have been replaced. The equipment house retains much original ‘Brush’ electrical power equipment, and analogue control and monitoring equipment, as well as modern replacements* for many of these items. A substantial amount of modern data cabling* is also present. Central in the room is the tall metal drum containing the cable-turner, which allows the cables entering the dish to rotate through 420 degrees. The Marconi Hut contains a modern diesel generator*.

The annular chamber has smooth concrete walls and contains modern cabling*. At the south-east it gives access to the tunnel to the control building, along which the cabling runs in wall trays*. The tunnel has plain shuttered concrete walls and extends to the original west wall of the control building, running beneath a later western control room extension*, which is not included. There are some modern sealant repairs*. The interior* of the swinging laboratory is plain.

*Pursuant to s1 (5A) of the Planning (Listed Buildings and Conservation Areas) Act 1990 (‘the Act’) it is declared that the aforementioned items are not of special architectural or historic interest.

This list entry was subject to a Minor Enhancement on 20/05/2019

History

The observatory at Jodrell Bank is one of the earliest planned sites for radio-telescopes in the world. As such it had a pivotal role in the development of the new science of radio astronomy which was one of the first steps towards modern Astrophysics, revolutionising our understanding of the Universe. The site was first used for academic purposes in 1939 when the University of Manchester's Botany Department purchased three fields in the Cheshire countryside covering around 11 acres. The earliest use of the site for radio astronomy occurred in December 1945 when Bernard Lovell, who worked for the university’s Physics Department, moved here to escape the radio interference that occurred in Manchester city centre. His first observations used ex-army radar equipment located at the south end of the site, close to two pre-existing botany huts. Subsequently his team expanded northwards with the continuing construction of more permanent buildings, and purpose-built aerials and telescopes to support their research. Jodrell Bank’s status as a world-class centre of on-going scientific research continues to this day with the construction of the global headquarters for the Square Kilometre Array project linking hundreds of telescopes and aerials in South Africa and Western Australia.

The first paraboloid radio telescope in the world (of 30ft diameter) was built in 1937, by Grote Reber, and could be tilted (in elevation) but not turned (in azimuth). The Lovell Telescope was first conceived by (Sir) Bernard Lovell in 1948, as a means of building on the success which had by then been achieved at Jodrell Bank with the (fixed) Transit telescope, which could only survey the sky close to vertically above it at any time. Such was the engineering challenge presented by the idea that the first firms approached expressed incredulity, but in September 1949 the engineer Sir Charles Husband confirmed it could be done. The concept was based on the 30Ft telescope which had been erected at Jodrell Bank in 1949 with a similar mounting - but scaled up to deal with wavelengths up to c20m, and to compensate for the extreme weakness of the signals.

Construction began in September 1952, with piling down to over 90ft in places. The original design presented many unsolved engineering problems, and redesigns were required both due to changing performance parameters as the field advanced and to continual funding problems. In an age before digital computing, the calculations alone for the cylindrical space-frame supporting the bowl (instead of the originally envisaged rear girder) took a year. Other substantial problems included how to move 2,000 tons with accuracy at a quarter of an inch per minute (with variable wind loading), how to avoid wind flutter of the kind that destroyed the Tacoma Narrows suspension bridge in 1940, and how to compensate for the changing weight distribution as the dish was elevated and depressed as it turned.

When completed, the telescope comprised a bowl of over 7,000 steel plates, true to within 1in and of 250ft diameter and 62ft 6in depth, with a mast-mounted receiver at the focus, in the plane of the aperture in order to protect it from interference. The bowl was supported by the cylindrical space-frame around it. The space-frame was attached at either side by trunnion bearings at the top of two 186ft-tall towers with legs raking forwards and rearwards. The elevation drive at these bearings used racks from 15in gun turrets from the former battleships HMS ‘Royal Sovereign’ and ‘Revenge’. The towers were each supported by six four-wheeled bogeys, each running on one of two concentric tracks formed of a double rail, with an outer diameter of 353ft – two of each tower’s bogeys were driven by 50HP motors at the foot of the tower. The two rails were level to within 1/8in across the ring, with the outer one 3/64in higher than the inner one, and expansion joints arranged so that only one of the 48 wheels of the bogeys was passing over them at any time. The rails were laid on a circular bed of over 10,000 tons of reinforced-concrete with an annular chamber at its centre, accessed by a tunnel from the adjacent control room. A large girder linked the two legs across the diameter of the rails, with a pivot mounted centrally within the annular chamber. Within the lattice-work girder, above the pivot, was a corrugated-steel room housing power and electrical equipment and the apparatus for turning the various data and control feeds with the horizontal motion of the dish. Above this room, a lattice semi-circular stabilising girder ran vertically behind the dish. A small steel laboratory (pivoted to remain level whatever the elevation of the dish) was attached to the underside of the dish’s supporting lattice, near the centre.

The dish was moved in azimuth under power for the first time on 12 June 1957, and on 20 June it was tilted for the first time. The first recording of signals received by the dish took place on 2 August. On 9 October, automatic remote control was achieved for the first time, from the control room via servo loops. The commands were calculated by a novel electro-mechanical analogue computer. Due to the launch of the Russian Sputnik 1 satellite, the dish was hastily adapted to track its carrier rocket, with signals observed on 11 October and confirmed the next night as it passed over the Lake District. On 16 October the rocket was detected at a distance of 1,500km.

The dish was a scientific tour-de-force. Despite the enormous development of the field it operated without major alterations for well over a decade, remaining competitive at short wavelengths and superior at those over half a metre. It was involved in an enormous range of work (much not envisioned at the time of building), including study of meteors, the moon and planets, the aurorae, the ionosphere, deep space radio sources, interferometry and the measurement of the size of distant radio sources, as well as the tracking and control of Russian and American early spacecraft, laying the foundations for the first manned moon landing on 20 July 1969. On 12 September 1959, at the request of the Russians, the Lunik II rocket was tracked to the moon, and in the control building JG Davies measured the Doppler shift caused by the moon's gravity. This technique was used in all subsequent tracking of moon approaches. Sources around the world, and Government advertisements at home, paid tribute to the vision and enterprise which resulted in the UK leading the way in this field of research. The telescope became a symbol of British pride and industrial prowess (a last-minute tender led to the appointment of Brush for the driving systems in place of the German manufacturer Siemens). Of Jodrell Bank’s physicists, roughly twice as many as the national average went into British industry or Government science. In engineering terms, too, the dish was internationally outstanding. It was the first fully steerable very large radio telescope in the world, and the largest telescope of any kind to that time; it is still one of the largest scientific instruments in the world, and still the third largest of its kind (it remained the largest for 14 years). Perhaps more remarkably, it has proved tremendously adaptable and continues to perform at the forefront of scientific discovery.

From 1967 to 1971, several major repairs and alterations were applied. The railway tracks were relaid, and an additional central track added. On this run the four bogeys of a cradle constructed around the diametral girder, supporting two new load-bearing semi-circular rear girders driven by high level bogeys, to assist in driving the dish in elevation. The original stabilising girder was removed to save weight. Other bogeys were repaired and replaced. A new, shallower receiving surface was constructed above the original surface, and the receiving mast stiffened and extended to move the focus beyond the plane of the aperture. Some holes were cut in the original surface for the structure supporting the new surface, but the majority was retained. The analogue computer was replaced by the Ferranti Argus 104 digital computer that was first used to control the nearby Mark II Telescope. Following these changes the original, Mark I Telescope became known as the Mark IA. In 1976, diagonal bracing members were added running down from the towers to the diametral girder, which required the relocation of the ‘Marconi Hut’ (emergency generator house) nearer to the centre of the diametral girder. For its 30th anniversary in 1987, the telescope was renamed the Lovell telescope. From 2001-02 a second new reflecting surface was added, replacing the earlier new surface but retaining the original. The original surface is now (2017) however being replaced as it deteriorates in condition. Bogey wheels have also begun to be replaced. However, the majority of the original design remains part of the current configuration, and much fabric is still original although continual replacement is an expected part of future maintenance.

Reasons for Listing

The Lovell Telescope, a radio telescope of 1952-57 with later alterations, is listed at Grade I for the following principal reasons:

* Scientific importance: as the largest and longest-lived component of the Jodrell Bank Observatory, (one of the earliest planned sites for radio telescopes in the world), with a pivotal role in the development of the science of radio astronomy, revolutionising our understanding of the universe;

* Design interest: the enormous steel frame and reflector dish give the Lovell Telescope an impressive, sculptural appearance, producing a dramatic visual quality which captures in physical form the excitement of radio astronomy at this pioneering site;

* Engineering interest: when it was constructed this was the first fully steerable very large telescope in the world (in 2017 still only surpassed by two others), and the largest telescope of any kind, and its design required much engineering innovation;

* Degree of survival: despite considerable replacement of fabric and alteration, the essence of the dish’s original design remains, and has been complemented and enhanced by many of the later additions, in particular those by the original designer;

* Group value: the telescope has a strong functional and visual connection with the Mark II Telescope (Grade I), through the discipline of interferometry for which the Jodrell Bank Observatory has a long-standing international reputation.

External Links

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