From Arecibo Observatory to Herouni Telescope in Armenia

Arecibo Observatory: The Hanging Giant

Completed in 1963, the Arecibo Observatory was once the largest single-aperture radio telescope in the world, featuring a vast 305-meter-wide dish embedded within a natural limestone sinkhole. Located near the city of Arecibo in Puerto Rico, it was initially designed to study the ionosphere but later became a vital tool for space exploration and radio astronomy. The observatory's design included a cable-mounted steerable receiver, along with several radar transmitters placed 150 meters above the dish.

Assembly of cables supporting reflecting dish. 1963

The dish itself was fixed to the Earth, which meant it could only point to the section of the sky directly overhead. To overcome this limitation, the designers opted for a spherical dish instead of a traditional parabolic one. This choice allowed the telescope to receive signals from a broader range of angles, though it required careful adjustments for optimal functionality.

Aerial view of Arecibo Observatory in December 2012

The telescope's instruments were housed on a triangular platform suspended above the dish by steel cables, supported by three reinforced concrete towers positioned at the 4, 8, and 12 o'clock positions. These cables were crucial for maintaining the platform’s position and stability. As the telescope’s capabilities expanded, additional upgrades were made, including the introduction of the Gregorian dome in 1997, which housed additional reflectors to improve signal focus. While this upgrade enhanced the telescope’s performance, it also added significant weight to the structure. To support this added load, the observatory’s engineers reinforced the system with auxiliary cables, backstays, and tie-downs to maintain the platform's stability.

The beam-steering mechanism of Arecibo telescope

A sophisticated laser ranging system helped adjust the tension in these cables, ensuring that the platform remained perfectly stable and aligned within millimeter precision—an essential feature for such a sensitive scientific instrument.

For 53 years, from its completion in 1963 until 2016, Arecibo held the title of the world’s largest single-aperture radio telescope, until it was surpassed by the Five-hundred-meter Aperture Spherical Telescope (FAST) in Guizhou, China. Arecibo played a central role in research across several scientific domains, including radio astronomy, atmospheric science, and radar astronomy. It also contributed significantly to programs focused on detecting near-Earth objects and the search for extraterrestrial intelligence (SETI).

Scientists from around the world submitted research proposals for the observatory, which were rigorously evaluated by independent referees. Notably, NASA utilized Arecibo for projects like near-Earth object detection.

Here is a list of key discoveries made by the Arecibo Observatory:

1967: Arecibo discovered that Mercury’s rotation rate is 59 days, not the previously estimated 88 days.

1972: The observatory was used to simultaneously heat and observe the D- and E-regions of the ionosphere.

1974: Arecibo discovered the first-ever binary pulsar, a breakthrough that earned Russell A. Hulse and Joseph H. Taylor the 1993 Nobel Prize in Physics.

1975: S-band radar observations of Mars were made to support NASA’s Viking mission.

1981: Arecibo produced the first radar maps of Venus’s surface.

1992: The observatory discovered the first-ever exoplanet, followed by the discovery of an entire planetary system around the pulsar PSR 1257+12.

1994: Arecibo mapped the distribution of polar ice on Mercury.

1996: Arecibo detected the ionized helium layer in the ionosphere.

2006: The observatory made observations of ionospheric perturbations caused by a tropical storm.

2008: Arecibo detected methanimine and hydrogen cyanide molecules in a galaxy 250 million light-years away—key ingredients for forming amino acids.

2016: The observatory discovered the first-ever repeating fast radio burst, which showed that the source of the burst survives, ruling out certain models of catastrophic explosions.

2017: Arecibo discovered two pulsars that intermittently vanish and reappear, challenging the belief that pulsars are consistent, orderly timekeepers.

These discoveries underscore Arecibo's vital contributions to radio astronomy and space exploration.

Arecibo Observatory's collapse! Credits: Arecibo Observatory and U.S. National Science Foundation Facility

In the early 2000s, NASA began to reduce its funding for the Arecibo Observatory, which increased pressure on the National Science Foundation (NSF) to maintain financial support. In 2006, the NSF first suggested the possibility of significantly reducing its funding and potentially decommissioning the observatory.

In 2017, damage to the telescope from Hurricane Maria prompted the NSF to reconsider decommissioning due to the growing costs of maintenance. Following a series of cable failures in August and November 2020, the NSF announced its decision to decommission the telescope via controlled demolition, although other facilities at the observatory would remain operational.

The Arecibo Telescope during demolition process, December 2021

Before demolition could proceed safely, additional support cables at the Arecibo Observatory failed on December 1, 2020, at 7:55 A.M. local time, triggering a catastrophic collapse. In under 30 seconds, a supporting cable from one of the three towers broke, weakened by years of corrosion and moisture. This led to the suspended antenna falling more than 500 feet (150 meters) into the dish below, causing extensive damage to the telescope. The collapse marked a significant blow to the observatory, just months after an earlier cable failure had prompted the decision to decommission the facility

The observatory’s distinctive and futuristic design captured public imagination, leading to its inclusion in several film, television, and video game productions. It is famously featured in the climactic scene of the 1995 James Bond film GoldenEye.

Furthermore, Arecibo is one of the 116 images included in the Voyager Golden Record, a collection of humanity’s achievements launched into space on the Voyager spacecraft. Since 2008, it has been listed on the U.S. National Register of Historic Places, recognizing its significant contributions to science and popular culture.

ROT54: Armenia’s Celestial Eye

The ROT54 telescope in Armenia represents a distinct chapter in the history of astronomical exploration. Built during the Soviet era, this 54-meter radio telescope was designed to study astrophysical phenomena such as pulsars and cosmic microwave background radiation. Located in Orgov village, on the south slopes of Mount Aragats, Armenia’s tallest peak, the telescope’s position provided an exceptional vantage point for observing the universe.

The construction process of ROT54 telescope in Orgov village

Constructed between 1975 and 1985, ROT54 became operational in 1986, continuing its work until 1990, when financial and technical challenges led to its deactivation. A proposal to restore the facility emerged in the mid-1990s, leading to a modernization phase between 1995 and 2010. This upgrade included the installation of new control computers and updated feeds, and operations resumed in collaboration with the Astronomical Society of Russia and the National Technical University of Athens. However, in 2012, operations were halted again after a control arm failure immobilized the secondary mirror.

Herouni Mirror Radio Telescope (Зеркальный радиотелескоп геруни) Patent No. 1377941

ROT54 is composed of 4,000 mirrors and features a large two-mirror antenna with a 54-meter diameter, complemented by an optical telescope with a 2.6-meter diameter. During its operational years, the telescope made significant contributions to astrophysics. For instance, in 1985, it recorded a powerful radio flare from the red giant star Eta Gemini, a phenomenon that had never been observed before. The telescope's high sensitivity enabled it to detect faint radio emissions from distant stars and galaxies, contributing valuable data to the scientific community.

Additionally, ROT54’s remarkably low noise levels allowed its creator, Paris Herouni, to challenge prevailing cosmological theories. Notably, it was used to investigate the existence of the "relic background" and to test the Big Bang theory.

Aerial footage of ROT54

Similarities and Contrasts

Both Arecibo and ROT54 are prime examples of the power of large-scale radio telescopes in expanding our understanding of the cosmos.

The two observatories had their own destiny, however: Arecibo gained worldwide recognition for its groundbreaking discoveries, while ROT54 operated quietly within the Soviet Union, largely unnoticed by the rest of the world.

Me sitting in the control room of ROT54

Conclusion

The Arecibo Observatory and ROT54 telescope are monuments to human curiosity, innovation, and the pursuit of knowledge. Arecibo’s legacy lives on in the annals of space exploration, while ROT54 continues to inspire as a relic of Soviet ingenuity and Armenian heritage. Together, these observatories highlight humanity’s unyielding quest to understand the universe, and their enduring appeal ensures that the search for knowledge remains a universal endeavor.