1 Feb. 2024

NSF’s NOIRLab’s world-class observatories — Cerro Tololo Inter-American Observatory, Kitt Peak National Observatory, the International Gemini Observatory, and Vera C. Rubin Observatory — are built in some of the highest and driest locations on Earth, often situated far from major inhabited areas. This means that getting to and working on-site presents some niche challenges, but also provides astronomers with the opportunity to discover out-of-the-way and unique environments

The Gemini North telescope, one half of the International Gemini Observatory, operated by NSF’s NOIRLab’s, ranks #12 in the world for highest-altitude observatories.

In their endeavor to untangle the mysteries of the Universe, astronomers rely on high-quality data collected at large, highly in-demand observatories. To enable breakthrough discoveries, astronomical observations are aimed at acquiring data of the best possible quality, meaning observatories need to be located at the best sites the world has to offer.

For telescopes, optimal location means several things: as far as possible from light pollution; high altitude, to provide unobstructed views and to minimize the amount of atmospheric interference; and finally, situated somewhere that enjoys a lot of cloudless weather, as the vast majority of Earth-based telescopes are reduced to very costly lumps of metal in the face of cloud cover.

While working at these isolated sites can be a surreal experience, it can also present some unique challenges.

To meet these environmental needs, observatories tend to be located in some of Earth’s most remote places. Although in-person observing is becoming increasingly less common thanks to remote observing capabilities, some astronomers still find themselves at these isolated mountaintop observatories, including astronomers who wish to be present while their data is being collected as well as students and early career scientists who are becoming familiar with the telescopes they may one day use. Working at these sites can be a surreal experience, but can also present some unique challenges, testing visiting astronomers' adaptability to unfamiliar conditions.

As an example, Cerro Tololo Inter-American Observatory (CTIO), home to around 40 telescopes including the Víctor M. Blanco 4-meter Telescope, is located in a mountainous region of Chile in South America, about 80 kilometers (50 miles) inland from the coastal city of La Serena, on the peak of Cerro Tololo. And a 35-minute drive away is the neighboring mountain Cerro Pachón, the location of the Gemini South telescope, one half of the International Gemini Observatory, as well as the 4.1-meter Southern Astrophysical Research (SOAR) Telescope and the Vera C. Rubin Observatory, currently under construction.

Access to both of these sites is via a long, winding road through a rocky desert landscape. Although the drive from La Serena is only a couple of hours, visitors are often advised to arrive a day early so that they can acclimate to the altitude, which at 2207 meters (7240 feet) for CTIO and 2722 meters (8930 feet) for Cerro Pachón, is well above the threshold where some people will start to experience altitude sickness. In such a remote location, certain resources — like major medical services — are over two hours away. Thus, staff and visitors may need to rely on old-fashioned, but reliable, technology such as hand-held radios to get hold of help from the on-site paramedic and nurse services should they be needed for anyone feeling the effects of the thin air.

Luckily, special dormitories provide visiting astronomers a place to retreat at the end of a long night of observing. These accommodations are not exactly Airbnb’s but they do offer the basics: bed, fridge, microwave, and even wifi — plus the all-important blackout shades for daytime sleeping. And just beyond their front door, guests might occasionally spot local wildlife such as vizcachas, foxes, cougars, parrots, condors and various varieties of insects.

Despite the challenges, visitors to CTIO and Cerro Pachón can expect to be mesmerized by the spectacularly clear southern hemisphere night sky. Some astronomers even recount standing outside on a moonless night and seeing their shadow created by nothing more than the star-speckled band of the Milky Way.

Over 10,000 kilometers (6213 miles) away in the northern hemisphere is Gemini South’s twin telescope, Gemini North, located near the summit of the dormant Hawaiian volcano, Maunakea. With an impressive altitude of 4214 meters (13,825 feet), Gemini North has the distinction of being at (by far) the highest altitude of all the NOIRLab observatories. For that reason, despite being only a relatively short 70-kilometer (44-mile) drive from its nearest city, Hilo, the observatory can feel exceptionally isolated, with some describing being on-site as having the uncanny feeling of being on a different planet.

Though the majority of visiting astronomers will stay and work from the base facility in Hilo, those who travel to the summit may have the chance to enjoy the extraordinary experience of looking up at clear skies while looking down onto the top of a roiling cloud bed: a sight that many of us can only experience from an airplane.

Across the Pacific Ocean in the southwestern US state of Arizona is Kitt Peak National Observatory (KPNO), located about 88 kilometers (55 miles) from the nearest city, Tucson. KPNO sits at an altitude of 2096 meters (6876 feet) in the Quinlan Mountains, one of many isolated mountain ranges in southeastern Arizona known as sky islands. The national observatory resides on land belonging to the Tohono O’odham Nation on the summit of Kitt Peak, which is known as I'oligam Du'ag to the Tohono O’odham. KPNO comprises 200 acres of the nearly 3 million acres of the Nation and offers visiting astronomers a chance to see some of the Arizona-Sonoran Desert’s unique geology, flora and fauna.

Because of the observatory’s altitude and desert location, the nights can get cold, even during the summer months. And the observatory does not have a large number of staff at night, meaning that things can get eerily quiet on site. One astronomer recalls being accidentally locked outside a telescope building for an hour in the middle of an observing night with no cell service — a testament to the importance of always carrying a safety radio. Her colleague just assumed that she was enjoying the extraordinary view of the night sky, when actually she was getting unexpectedly chilly!

Visiting NOIRLab’s remote mountaintop observatories is truly a unique experience. This brief overview gives a small taste of the treasures and trials that come with in-person astronomy observations and the (literal) lengths that astronomers are prepared to go to learn about our Universe.


Eleanor Spring
Eleanor Spring has over 5 years of professional science writing experience for organizations including the European Southern Observatory and NSF’s NOIRLab. She’s happily settled in the Netherlands where she is currently completing a PhD studying exoplanet atmospheres at the University of Amsterdam.

NOIRLab Stories