Yebes Observatory RT40m
The Yebes Observatory RT40m, or ARIESXXI, is a radio telescope which is part of the observatory at Yebes, Spain.
It is a 40-metre Cassegrain–Nasmyth telescope.
Location
The telescope is located at Yebes Observatory.Yebes Observatory is the main scientific and technical facility of the National Geographic Institute of Spain.
The observatory is located around to the North-East of Madrid in the province of Guadalajara in the autonomous community of Castilla-La Mancha. It sits at an altitude of 931 metres above sea level and enjoys excellent observing conditions year-round. The precipitable water vapour level is less than 6 mm and reaches a minimum of 2 mm in the winter. The wind velocity is less than 5 m/s for the majority of the year and the number of days with rain or snow is less than 1 week annually.
The Technological Development Centre facilities include two radio telescopes, a solar tower, an astrograph and a Gravimeter. The most powerful telescope is the newly constructed 40 m telescope which was completed in 2005 and saw first light in ¿May 2007?. ARIESXXI was specifically designed to be integrated in the European Very Long Baseline Interferometry network as well as operating as a single dish. It currently has active receivers in S-Band, CH-Band, C band which is split in two sub-bands, X-band and K-Band. A 100 GHz receiver is currently being installed for millimetre wave VLBI. The CDT has advanced receiver laboratories on site that allows the dedicated team of more than 20 engineers and astronomers present to develop and optimize new and existing receivers. The R&D undertaken in the CDT under the mandate of the OAN permits it to share information and resources with the other important radio observatory in Spain, the IRAM radio telescope at Pico Veleta in Granada. This collaboration also permits the free exchange of ideas and personnel with IRAM's facilities in France and Spain and facilitates technology exchanges between sister institutes in other European countries which participate in the EVN.
History
The project "A Radio Telescope for Spain" was conceived from a series of National Development Plans for Radio Astronomy undertaken in the mid and late 90s. These plans culminated in a technical meeting in Madrid in the late 90s where the CAY personnel in conjunction with experts from all over Europe carried out an exhaustive study to define the characteristics required by such a telescope in order to participate actively in the international astronomy community. Once the appropriate homology and applications of the telescope had been selected a feasibility study was carried out with the fundamental objective of determining whether or not it was practical to construct such a telescope in Spain and if so how to maximize the participation of Spanish industry in said project. This study was undertaken by INISEL Espacio and finally the contract for the detailed design and construction was awarded to a German company with a long experience of design and maintenance of radio telescope and radar dishes, MAN Technologie.Thus the initial construction work began in 2000 with the pouring of foundations and the placement of the concrete pedestal, built by ACS, that would support the telescope reflectors and associated support structure. The same year saw the production of the azimuth and elevation bearings by Rothe-Erde and FAQ of Germany respectively. 2000 also saw the construction of the steel back-support structure for the telescope by Schwartz-Hautmont Construcciones Metálicas of Spain. The contract for the design of the focal plane optics was awarded to ESTI of the Technical University of Telecommunications in Madrid to couple the Cassegrain focal plane radiation to the receivers. In 2001 the contract for the manufacturing of the surface panels of the primary and secondary reflectors was awarded to Schwartz-Hautmont and then installation of the servo-motors to BBH of Germany. Finally in 2003 the electrical installation was completed by ELIMCO of Spain.
Commissioning began in ¿2005? and finished in 2007.
Telescope properties
| Parameter | Value |
| Dm | 40m |
| Ds | 3.28m |
| Lv | 1.204m |
| Lr | 25.396m |
| Fm/Dm | 0.375 |
| Fm | 15m |
| Feq | 316.6 |
| Feq/Dm | 7.9 |
| Mag | 21.09 |
| Fc | 26.6m |
| g | 11.6m |
| g' | 6.6m |
| hp | 6.667m |
| hs | 7.129m |
| Theta | 3.621° |
The ARIESXXI radio telescope is an alt-azimuthal design with a rotating head above an azimuthal bearing or turning head. It has full 360-degree movement in azimuth and horizon to horizon coverage in elevation. As previously mentioned the telescope is Nasmyth-Cassegrain model that consists of a parabolic primary reflector and a hyperbolic secondary reflector that brings the dual system to a focus some 11 metres below, within the structure of the telescope housing, via a beam-guide. The optical configuration of the tertiary Nasmyth system is such that the focus is always maintained in the same place as the flat Nasmyth mirrors track the movement of the principle axis of the dual reflector to ensure a constant illumination of the receivers. This allows the receiver antennas to remain fixed in position and greatly simplifies the opto-mechanical design of the receiver suite.
The sub-reflector can be displaced axially through focus to aid in correcting defocusing effects during telescope slewing caused by gravitational/elevation deformations. It is a hollow structure that permits the mounting of a holographic receptor within which will be used for determining the surface accuracy of the primary reflector panels.
The telescope design follows the principle of homology. It can operate in winds up to 15 m/s and a maximum wind speed of up to 50 m/s can be withstood without structural damage being sustained. The surface accuracy can reach at least 150 microns RMS with a maximum accuracy of 75 microns RMS achievable. In order to attain this level of planarity each individual panel must fulfill a surface accuracy of 60 microns. A minimum planarity of 150 microns allows operation up to 125 GHz applying the Ruze condition of λ/16 with an upper threshold frequency of 250 GHz in the case of 75 microns accuracy. The measured inefficiencies of ARIESXXI are ?% at ? GHz which compare to a theoretical maximum of 78% for a blocked Gaussian illumination and with a constant edge taper of −10.9 dB at the sub-reflector.
Optics
The optical system consists of three main components:The Primary Reflector
The Secondary Reflector
Nasmyth Mirrors
Tertiary Optics
Receivers
ARIESXXI boasts an unusually large receiver cabin which permits the housing of a large number of receivers. The cabin currently houses six receivers all of which reside in one of the two optical branches available. The orientation of the Nasmyth mirrors can also be altered to 0° and 20° if required to include additional optical paths and which substantially increases the number of receptors which can potentially be placed in the cabin. The receiver currently installed are as follows :S-Band
CH-Band
C-Band
X-Band
K-Band
Q-Band
W-Band
Back ends
ARIESXXI utilizes the MarkV correlator backend system based on solid-state storage (as opposed to the MarkIV system which used magnetic tapes.Science
The telescope observes both as a stand-alone telescope, and as part of VLBI networks. Up to 30% of its observing time is available to astronomers on a global basis.VLBI
Since 2008, the telescope has been used for Very-long-baseline interferometry for both astronomy and geodesy. It is part of the European VLBI Network, the Global mm VLBI Array, and the International VLBI Service for Geodesy and Astrometry.Single Dish Observations
The telescope is also used to observe spectral lines from interstellar molecules in circumstellar envelopes, the interstellar medium, and extragalactic sources.Observation types.