New Research Life for Retired Technology. The Tulancingo Radio Telescope

With the urging and support of colleagues at the universities of Leeds and Oxford in the UK, UNAM researchers and technicians are converting a retired telecommunications antenna into a professional-class radio telescope.

Located in Tulancingo, Hidalgo, the 32-meters antenna Tulancingo-I was built just in time to broadcast the 1968 Summer Olympics via satellite to the world, and it also served to bring Mexico into the modern world of telecommunications. Decades later, with improved electronics and the development of fiber optic communications, these large telecom antennas have been retired from service.

With financial support from the Newton Fund of the United Kingdom, the government of Hidalgo State, and UNAM’s Coordination of Scientific Research, a conversion project was launched to upgrade the antenna infrastructure to the much more demanding specifications of a radio telescope.

With technical assistance from the National Institute of Astrophysics, Optics, and Electronics in Puebla, the National Astronomical Observatory in San Pedro Mártir, and the University of Oxford, UNAM researchers have already passed the “first light” stage—the first successful observation of an astronomical object. Throughout 2025, they will continue with various commissioning tasks and expect to have the telescope fully functional in 2026. 

The radio astronomous community has been using 32-meter class single-dish radio telescopes since the 1960s. In fact, Luis Rodríguez, a pioneer of radio astronomy in Mexico, did his doctoral studies at Harvard University in the 1970s using a single-dish telescope only slightly larger (37 meters) than the Tulancingo antenna.

If radio astronomers have been using this type of telescope for over 50 years, one might reasonably ask if there’s still anything worthwhile left to do. The answer is a resounding yes! Here, we describe three of the more important possibilities. 

First, there is a specific class of niche research projects where high sensitivity and high angular resolution are not essential. Instead, what is critical is lots of telescope time on a regular basis. Many radio telescopes, such as the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, are overcrowded, with astronomers requesting up to ten times more hours than are available on the telescope. In such a situation, it is impossible to observe the same source repeatedly, every week or two, during several years. The Tulancingo telescope is ideal for such projects. One example relates to an astronomical phenomenon known as a “methanol maser”, where methanol molecules close to a young star show very intense emission in a laser-like form, but in microwaves, hence they are called masers. It is well-known that such masers’ intensity can vary and 15 years ago, it was discovered that some of these masers’ variability is periodic, showing flares of emission every few hundred days with amazing regularity. The cause of this periodic behavior is not yet known, but an intriguing possibility is that it corresponds to the alignment of planets around the young star. Determining the periodicity of these masers requires monitoring observations of the same source over multiple years—the sort of project that could be carried out at Tulancingo.

A second application of the 32-meter telescope is teaching. Because radio telescopes such as the Large Millimeter Telescope (LMT) and ALMA are in such high demand by radio astronomers, only very advanced students can obtain time there, and even then, they will not get any “hands-on” experience, as  these telescopes are operated by observatory staff. The Tulancingo telescope will be available for high school to graduate level students. Internet will allow students to access  the telescope not only from Mexico but from around the world, and they will be able to control the antenna and make astronomical observations. For more advanced students in Mexico, practical training at the telescope site in Tulancingo will provide a much richer learning experience than is available elsewhere.

Finally, the “killer-app” of the telescope is to join an international radio telescope array along with other telescopes, particularly in Europe. In these arrays, all the antennas work together to produce incredibly high angular resolution images. Using a technique called Very Long Baseline Interferometry (VLBI), the signals received at each antenna are combined, often days or weeks after the observations, to produce images whose angular resolution corresponds to that of a single antenna with a diameter of 10,000 kilometers. The ability to produce such high-resolution images allow studying many other astronomical objects out to the edge of the known universe. The European VLBI Network would benefit enormously by including the Tulancingo antenna because the geographical separation from their antennas to Mexico is so large.

The antenna conversion began as a collaboration between UNAM and British universities and will soon bear fruit, providing Mexico with international collaborations on several continents as the Tulancingo telescope takes its place on the world stage.

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