[2][3] The observatory is located around 50 kilometres (31 miles) to the North-East of Madrid[3] in the province of Guadalajara in the autonomous community of Castilla-La Mancha.

The Technological Development Centre (CDT) facilities include two radio telescopes, a solar tower, an astrograph and a Gravimeter.

ARIESXXI was specifically designed to be integrated in the European Very Long Baseline Interferometry network (EVN) as well as operating as a single dish.

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.

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.

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.

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.

The optical system consists of three main components: The Primary Reflector The Secondary Reflector Nasmyth Mirrors Tertiary Optics ARIESXXI boasts an unusually large receiver cabin (8 × 9 x 3.5 metres) which permits the housing of a large number of receivers.

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.