National monument

Description

Preface

RADIO TELESCOPE WITH CONTROL HOUSE, situated southeast of Dwingeloo, on the border of forest and heath, on the edge of the National Park Dwingelerveld. Because of the equipment’s susceptibility to interference, the maximum 30-meter-high object was built at a peripheral location in order to minimize the chance of external (electromagnetic) vibrations. The building started in 1954 (autumn), in mid-1955 the construction work was finished, also the phase in which the reflector or mirror was placed on the tower. The installation of the drive equipment and the electrical equipment was completed in April 1956. On 17 April 1956, the radio telescope with operating house (at the time the largest radio telescope in the world) was officially put into operation by H.R.H. Queen Juliana. The object contains, among other things, a large parabolic reflector (often called “mirror”) and a sensitive, low-noise radio receiver, with which radio waves from the universe can be collected and the sun and galaxy can be observed continuously and systematically. The Leiden professor Jan Hendrik Oort stood at the base of the investigation into the structure of the galaxy and developed plans for observing the radio waves of the Milky Way. Oorts discoveries led to the development of a high-quality technical-scientific apparatus for making astronomical observations and related radio-astronomical research. Engineer C.A. (Lex) Muller, fellow-worker of professor Oort, delivered the design of the radio telescope and supervised with B.G. (Ben) Hooghoudt the construction work. The realization was in the hands of Werkspoor since 1954. Other, also Dutch, companies and organizations involved in the construction were Heemaf N.V. in Hengelo (design and realization of the electrical installation), Langhout engineering and architectural firm in Amsterdam (design concrete foundation), Amsterdam Ballast Mij N.V. in Amsterdam (realization concrete foundation) , Metal company Rademakers N.V. in Rotterdam (design and realization coordinate transformer, the “pilot”), principal the Netherlands Foundation for Radio Astronomy in collaboration with the Laboratory for Electronic Developments of the Royal Navy in Oegstgeest, Philips Physics Laboratory in Eindhoven and PTT Dr. Neher Laboratory in Leidschendam (design and realization of servo control). The object weighs 120 tons and has no longer fulfilled its original scientific function since 1988 (remark by CAMRAS: since 1998). The tenant of the radio telescope, the CAMRAS Foundation, aims re-use by amateur astronomers and radio amateurs and stimulates the educational function of the object.

Description

The high mounted steel structure (“the mirror”), somewhat similar to a spider web, has a diameter of 25.00 m, a bowl depth of 3.25 m and is equipped with tinned metal mesh (steel) with a reflecting surface. In 1978 (remark by CAMRAS: in 1969), stainless steel mesh panels were installed. The construction of this parabolic mirror count as hyperstatic due to the triangular system that has been implemented consistently, and consists of edge and filler bars and various anti-buckling bars, furthermore of quadrants, counterweights, focus box and a focus box construction. The antenna is movable in all directions and has an automatic tracking mechanism. The entire radio telescope is rotatable around a horizontal axis and suspended from a beak-shaped steel skeleton (necessary to bring the mirror into the azimuthal position). It is a 15.00 m high robust half-timbered form structure, constructed from tube bars. The basis of this steel skeleton is a square steel frame with a side of 11.70 m and contains the control house. The flat-topped control house is rotatable and always behind the reflector. It consists of a steel frame with fiber-reinforced concrete slabs for walls and roofing. Double glazing has been installed in the window frames; skylight. Inside, including a receiver room, engine room and observation room. Drive by means of servomotors and electric motors. The electrical equipment in the control house consists of, among other things, panels with push buttons and signaling for manual operation, setting buttons and indicator scales of the coordinate transformer, as well as the time clocks for solar and sidereal time and a panel with the chart recorder on which measurements of the 21 cm receiver could be recorded (the recorder has not been used as such since the 80s of the twentieth century, but since then has provided the monitoring function of external interference signals). In 1993, the pilot control was removed and replaced by direct operation from a control computer. The object has three steel stairs: between the ground level and the control house, whilst between the control house and the mirror a two-part staircase with a platform leads to/from the tower top and provides access to the elevation-drive mechanisms and the equipment in the top of the parabola. The object has two drive systems: one for the azimuth movement and one for the elevation movement (elevation drive completely renewed in 1987) (remark by CAMRAS: both drive systems have been thoroughly modified several times). The drive system for the elevation movement consists of two separate systems. The whole is mounted rotatable on a spindle, is carried by the spindle and the four wheels on a circular rail and rests under ground level on a rigid foundation, a ring of reinforced concrete with a diameter of about 17.00 m, provided with a weighted base.

Appreciation

The movable RADIO TELESCOPE WITH CONTROL HOUSE represents historical scientific interest based on the international and innovative role the object played in mapping the Milky Way, the universe and the discovery of the nearby large galaxies. The construction of the radio telescope with engine room is almost in original state, so it has authenticity value and historic-building significance. The radio telescope with control house in Dwingeloo is the last of former three telescopes of this type and represents high rare value. The leading position of the Netherlands in the internationally oriented astronomical world can largely be traced back to the object. In the control house belonging to the radio telescope, the technical inventory and layout are largely retained; besides the significance for the history of technology and science, the engine room offers the completing half of the two-unity that it forms together with the radio telescope. The object guarantees a remarkable historical sensation because of the dimensions, construction, age, striking appearance and solitary position, especially as it forms a contrast with the natural environment in which the radio telescope with the control house is located, on the edge of the National Park Dwingelerveld, in a rural area with expansive views. The (radio interference-free) situation has remained unaffected since the construction and contributes to a large extent to the historical significance, experiential value and expressiveness of the radio telescope with operating house to be classified as a landmark.