ALMA: The World’s Highest Observatory

James Johnson Exploration

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We are a curious breed. Our curiosity has been behind some of the greatest inventions of all time from the wheel to harnessing nuclear energy for power. The same curiosity has pushed us to explore and discover everything from the Americas and new trade routes to witnessing briny water flows on the surface of the planet Mars. But one curious question has transcended time “How did the universe in which we live begin?” For millennia, we have tried to peer deeper into the cosmos and subsequently back in time to search for clues in satisfying this long-lived curiosity. The quest has led us to build ever larger celestial observatories at increasingly higher altitudes and even in orbit around the Earth. Among the desolate beauty of Chile’s Atacama Desert, one can find the greatest of these observatories to ever be constructed. The Atacama Large Millimeter/submillimeter Array (ALMA) is the highest radio observatory in the world and is focused on investigating the earliest moments of time.

ALMA Antenna

One of 66 different antennas that make up the Atacama Large Millimeter/submillimeter Array (ALMA) Observatory.

But how can we look back in time? It’s as easy as looking up. The glimmering light of the stars we see above us are thousands, millions, and even billions of years old. Because of the large distances between us and the stars we see in the sky, the light we observe today was first emitted from a time long ago – even before the Earth itself had formed. As we peer at the furthest stars we are literally travelling back in time. Our ultimate goal is to witness the first moments of the “Big Bang,” but that is a difficult challenge.

Big Bang

The scale of time ALMA is investigating –the earliest moments of the universe [Print Credit: ALMA Observatory].

There are many enemies in being able peer deep into the beginning of the universe. Our atmosphere and the water moisture it contains, the ability to construct large and precise antennas or telescopes, and the cost for operating and maintaining such devices all work against our ability to look back in time. The ALMA observatory is currently the world’s greatest attempt to tackle these challenges and see further back in time than ever before.

ALMA Antenna Close-up

ALMA tackles the challenges of peering back in time through its location, technology, and innovative use of antennas.

As the highest observatory in the world, perched at an altitude of 5,000 meters (~16,400 feet), ALMA has less of Earth’s atmosphere to have to peer through during its research. With the added benefit of being in one of the world’s driest landscapes, there is also less moisture, meaning ALMA has one of the clearest views of the deepest points in space. While a clear view is important, having large and precise instrumentation is even more critical. In the past, being able to look back in time meant needing larger antennas and telescopes. The bigger they got, the more challenging it would be to maintain precision and accuracy and the more costs would skyrocket. With advances in modern computing however, one can now link together information gathered on numerous, smaller antennas and telescopes to effectively create one large unit. This is called building an array and is the key to ALMA’s ability to lay claim to the title of most powerful observatory in the world, effectively providing the same capability as a gigantic 16 km (~10 mile) wide antenna!


ALMA’s Operational Support Facility (OSF) is at 2,900 meters (9,500 feet) supporting up to 66 antennas at 5,000 meters (16,400 feet), offering a moderately dry and clear view of the stars.

ALMA Array

A collection of 7 antennas at ALMA’s Array Operations Site during its early development [Credit: ALMA (ESO/NAOJ/NRAO), W. Garnier Acknowledgement: General Dynamics C4 Systems]

ALMA collectively uses up to 66 radio antennas ranging in size from 7 to 12 meters (23 to 39 feet) in diameter to hone in on the center of the universe. Located high on the Chajnantor plateau, the antennas have another unique feature – they can be completely repositioned. A total of 197 fixed bases provide plenty of opportunities to reconfigure the array to individually suit each study proposed to ALMA. Moving the antennas almost mirrors how NASA used to move space shuttles to the launch pad. Two large crawler-transporters can pick up and move the antennas from one base to the next, or down to ALMA’s Operational Support Facility (OSF) at a more manageable 2,900 meters (~9,500 feet) for maintenance. And yes, the crawler-transporters have names. Otto and Lore were made in Germany and are just one contribution of many as 21 nations collaborate to increase our understanding of the universe.

AMLA Antenna Display

A total of 66 antennas are currently available for use at ALMA, although studies or system maintenance may cause less to be active.

Collectively, Collectively, 25 antennas from the European Southern Observatory (ESO), 25 from the National Radio Astronomy Observatory (NRAO) in the United States, and 16 from the National Astronomical Observatory of Japan (NAOJ) currently serve ALMA. While not all antennas are operating simultaneously due to maintenance or the needs of the scientific study, they all are built to the same standards for accuracy. Each antenna is accurate to less than the thickness of a sheet of paper and house super sensitive receivers as they ‘listen’ to the electromagnetic waves being emitted from the earliest beginnings of time. To maximize the efficiency of the receivers, they are cooled using  helium gas to minus 269 degrees Celsius (~-516 degrees Fahrenheit). As the antennas are focused on a particular part of the universe, they collectively absorb the incoming electromagnetic waves and send the corresponding signals to a supercomputer also located high on the Chajnantor plateau. In fact, the computer is among one of the most powerful computers in the world as it uses 134 million processors to combine and process the signals coming in from the antennas.

AMLA engineer

An ALMA engineer performs work on one of the antenna’s sensitive receivers.

Once the incoming signals are processed, they travel to ALMA’s Operational Support Facility along with data on each antenna’s operation. Scientists and engineers scan through the data in the facility’s control room to both ensure the safe and effective operation of the array as well as to witness some of first scientific observations. With researchers participating in ALMA’s discoveries from all over the world, data is then distributed to universities and scientific institutions across the planet.

ALMA Operators

Scientists and engineers operate the array and monitor its data from the comfort of the Operational Support Facility.

ALMA made its first scientific observations in 2011 with just 16 antennas. From then on, the array has made astounding discoveries in six years of operation. Molecules of glycolaldehyde, a simple form of sugar which could serve as energy sources for life, were observed around a star called IRAS 16293-2422. Planet formation has been observed around a young star called HD 163296 where two planets about the size of Saturn are taking shape. Even the formation of galaxies nearly 10-billion light years away is being observed.

As ALMA continues to unlock the deepest secrets of the cosmos, it will be aided with other cutting edge observatories. The South Pole Telescope, Very Large Array, and soon-to-be launched James Webb Space Telescope will aid in investigating some of the furthest celestial objects in the universe. These facilities will enable us to peer back in time and answer our long-held questions about the earliest moments in our universe. Our curiosity, however, will never rest as discoveries will breed new questions. We will invent, build, and use new tools to continually quench our thirst for greater knowledge and understanding. ALMA is one giant step in satisfying humankinds’ greatest curiosities.

AMLA Antenna Segments

ALMA’s discoveries are enabled by technology and its innovative use of antennas.

Footnote – Visiting ALMA:

Visiting ALMA is relatively simple. If your travels bring you to the Chilean town of San Pedro de Atacama during a weekend, you can reserve a spot for a free tour of ALMA’s Operational Support Facility through their website. The tour includes transportation to and from San Pedro de Atacama and is provided in both English and Spanish. While public visits to the full array are not possible due to the altitude, we can attest to the visit being an amazing peek into one of the world’s most ambitious engineering and scientific projects. More details are available here:

About the Author

James Johnson


James is an innovation storyteller and photographer for Simple Discoveries. He's previously served in NASA’s Mission Control for 18 Space Shuttle missions and is passionate about cultivating innovation through personal exploration and discovery.

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