History

In 1974, the National Geographic Institute opened a new line of research in astronomy to boost the activity of the National Astronomical Observatory and decided to create an Observatory in the town of Yebes, equipped with three astronomical observation instruments: a double astrograph for observing asteroids, a solar tower and a radio telescope with a diameter of 14 m. The latter instrument is the most unique and relevant of all the above because it was around it that the first Spanish radio astronomy group was formed. This last instrument is the most singular and relevant of all the above because the first Spanish radio astronomy group was formed around it. Astronomical observation at radio wavelengths provides valuable information about the Universe that cannot be obtained through optical observations. From its beginnings until today, radio astronomy has contributed to clarify physical processes such as the formation of stars or phenomena such as the detection of black holes.

Since there was no tradition or previous experience in Spain, the astronomers who joined the Observatory travelled to the main foreign radio astronomy centres, located in France, Germany, the United States and Sweden, to train in observing techniques, the operation of radio telescopes, the scientific exploitation of radio astronomical observations and the construction of microwave receivers. From the very beginning, it was evident that it was necessary to staff the Yebes Observatory with astronomers and engineers following the same criteria as the main radio astronomical observatories in the world. On the other hand, the variety of instrumentation needed to operate a radio telescope required the specialisation of the Observatory's members. In this way, the Observatory was configured from the beginning with a double facet: scientific and instrumental.

The first manual observation with the 14 m radio telescope was carried out on the Moon in 1979 with a radio wavelength receiver on loan from French colleagues. In 1988, after years of work, the first receiver cooled to cryogenic temperature (-250 °C) was installed on the 14 m radio telescope, designed and manufactured entirely at the Observatory with the support of the School of Telecommunications Engineering of the Polytechnic University of Madrid.

One of the key elements of radio telescope receivers is undoubtedly the very low noise cryogenic amplifiers. The Yebes Observatory specialised in their design and manufacture very early on. This high-tech activity, which started more than 30 years ago, is still active at a very high competitive level today. Spanish technology in radio astronomy has required considerable investment in personnel and instrumentation during these 50 years. Today, its laboratories and workshops occupy an area of more than 1,000 square metres and are equipped with modern technology and specialised personnel.

The amplifiers produced at the Yebes Observatory have been installed in numerous radio telescope receivers around the world. It is worth mentioning their use in the IRAM receivers of the European Space Agency's HERSCHEL space mission and the receivers of several frequency bands of the Atacama Large Millimeter Array (ALMA), the most sensitive millimetre interferometer in the world at the moment. The performance of these devices is so high that they have also been used in communications with very distant (deep space) space probes, as well as in the recent field of quantum computing. A final step towards the state of the art has been the design of monolithic MMIC amplifiers with excellent resultsThe amplifiers designed and built in Yebes are already part of the scientific-technical evolution in radio astronomy, having been decisive in such transcendental and media discoveries as the clearest image of the environment of the black hole of the Milky Way: Sgr A*.

The 40-metre radio telescope, a new impetus for the development of our cryogenic receivers

At the end of the 1990s, in view of the ageing of the 14 m radio telescope and its limited possibilities, the possibility of equipping the Observatory with a large modern radio telescope, which would also allow the study of the interstellar medium with great sensitivity, began to be studied. After years of intense technological and managerial efforts, in the year 2005, a 40 m diameter radio telescope was inaugurated, currently the most significant instrument at the Yebes Observatory and the one that grants the status of ICTS to the Observatory since 2013.The 40 m radio telescope saw its first light in 2007, observing once again the Moon, and immediately joined the European Very Long Baseline Interferometry (EVN) network, becoming one of its key components due to its high sensitivity and reliability. For over 10 years, this radio telescope has also been a part of the geodetic network of the International VLBI Service (IVS), which determines Earth's orientation parameters in space.

The use of the radio telescope is open to astronomers worldwide through an open and competitive access process with a proposal evaluation committee.

The commissioning of the 40 m radio telescope marked the beginning of a new stage of technological developments at the Yebes Observatory. To fully exploit all the capabilities of the new radio telescope, it was necessary to construct new low-noise cryogenic receivers.

Its manufacturing is a highly specialized endeavor involving engineers, electronic and mechanical technicians, all with advanced expertise. The process begins at the engineers' workstations with designs for the feed system, cryostat, amplifiers, and converters. Subsequently, it moves to laboratories and workshops where highly skilled technicians carry out the construction. The components are then extensively tested for weeks in measurement laboratories before being finally installed in the radio telescopes. This process spans months, engages workers from various disciplines, and once again demands a substantial deployment of resources in terms of personnel and financial investment.

Currently, low-noise cryogenic receivers have been constructed for other institutes and observatories worldwide upon request.

Thanks to the efforts made, the 40 m radio telescope is one of the most comprehensive instruments globally in this frequency range, particularly within VLBI networks. The experience gained since the construction of the first receiver has uniquely positioned the Observatory among the few centers worldwide with such capability.

RAEGE and Space geodesy, the ultimate boost

In 2012, to enhance the field of radio astronomy observations for geodetic purposes, IGN (National Geographic Institute) and the Regional Government of the Azores signed an agreement to create the Atlantic Network of Geodynamic and Space Stations (RAEGE). This network consists of four 13.2 m diameter radio telescopes strategically located in Spain and Portugal: in the municipality of Yebes (on the Eurasian tectonic plate), on the islands of Gran Canaria and Santa María in the Azores (on the African plate), and on the island of Flores in the Azores (on the American tectonic plate). This network will accurately determine the relative movement of the three tectonic plates on which the radio telescopes are situated. The first element of the RAEGE network, the 13.2 m radio telescope at the Yebes Observatory, was inaugurated in 2013. In 2014, the radio telescope on the island of Santa María was constructed, and the construction of the radio telescopes on the islands of Gran Canaria and Flores is planned for the coming years.

These radio telescopes, in addition to conducting regional studies, will be integrated into the global project VGOS (VLBI Geodetic Observing System), the next major initiative of the IVS (International VLBI Service). The goal of VGOS is to establish a reference system on the Earth's surface with accuracies better than 1 mm. This system will be used to determine the Earth's relative orientation in space with the utmost precision and to provide a ground reference for satellites orbiting our planet.

The momentum from the RAEGE project has been crucial in further advancing the technological capabilities of the Yebes Observatory. A notable example is the VGOS project, which requires the radio telescopes in its network to be equipped with new broadband receivers. In 2013, the design of the first broadband receiver began in the Yebes laboratories. At that time, only one similar receiver existed worldwide, located at the Haystack Observatory in the United States. Its construction was completed in early 2016 and was installed a few months later on the 13.2 m radio telescope at the Observatory, replacing the previous triband receiver, also manufactured in Yebes. Its installation was a success, enabling the 13.2 m Yebes antenna to join the exclusive group of 5 telescopes worldwide at the forefront of the VGOS project.

Subsequently, similar receivers have been manufactured for other radio telescopes worldwide, and currently, the Yebes Observatory has produced half of the receivers for the VGOS network. Given the excellent results achieved by the Yebes broadband receiver and the auxiliary teams and subsystems it utilizes, the Yebes Observatory has been designated as a Technological Development Center for the IVS. The presence of 'made in Yebes' technology in the world of space geodesy and, consequently, in radio astronomy is now undeniable..

* Text adapted from: Entre el Cielo y La Tierra. Revista del Ministerio de Fomento, No. 694, pp. 3-11). Autores: Jose Antonio López Fernández (Subdirector General de Astronomía) y Pablo de Vicente Abad (Director del Centro de Desarrollos Tecnológicos del Observatorio de Yebes). IGN