San Pedro de Atacama and ALMA

Getting to the Atacama Large Millimeter/Sub-millimeter Array (ALMA) radio observatory is done via road. The nearest town with lodging is San Pedro de Atacama, a town of about 3900 people at an altitude of 2400m (7900 feet). Getting to San Pedro is also by car, about an hour and a half southeast from the city of Calama. Calama has an airport and takes the major jet flights from other cities in Chile.

Calama to San Pedro

Calama to San Pedro: about an hour and a half by car. (Imagery ©2016 Landsat, Map data ©2016 Google)

The landscape is at first barren in appearance, and one would be correct in keeping to this belief: No surprises… it is a desert! Most of the area is dry desert, dry, high-altitude desert. There are occasional stands of trees (government experiments) that run here and there in the regions between towns, but otherwise it is a hard packed sand, gravel mix with lava flows from the volcanic activity which is still very much alive. Arrival in San Pedro takes one off of the highway route 23 and into a world of high adobe packed walls, dirt roads and dust. The landscape is sparse, again from the viewpoint of driving around town. Behind those walls? There are some pretty nice homes in there, trees and gardens, hotels, restaurants, shops: it is a bustling little town full of things to discover and enjoy!

Arriving at San Pedro de Atacama

Arriving at San Pedro de Atacama, a small town with high walls.

People make their way about town on foot, bicycle, and car. One has to be very careful while driving, as there are no street signs, stop signs, warning indicators, etc, and the walls are too high to see around. It is not uncommon to have a swift-moving bicycle cross your path as you drive the streets.

San Pedro Streets

San Pedro Streets: there is a mix of foot traffic and cars everywhere one goes.

Each doorway can lead to any possible outcome! There are restaurants, clothing stores, textile shops, astronomy tourism centers… all located in there!

Streets of San Pedro

The streets of San Pedro – a dusty affair worth lots of investigation! Small shops and restaurants dominate the main part of town.

Located just off to the side of the main square (Plaza de Armas) is the San Pedro church, an active Roman Catholic church, and one of the oldest constructed in Chile. The church is now an historical site along with San Pedro’s oldest structure, Casa Incaica, which dates back to 1540.

Church of San Pedro de Atacama

Entrance to the Church of San Pedro de Atacama, reportedly the second oldest church in Chile, constructed in the 17th century. The patron saint of this Catholic church is Peter.

There are a lot of dogs making their living in San Pedro – they wander the streets and call the whole town their own. People lovingly care for all of them, knitting them sweaters, feeding them throughout the day, and giving a pat on the head. The little fella in the photo below followed us as we made our way to a local bakery – some of the finest croissants in Chile, I must say! He knew where to get a meal!

San Pedro puppies

There are also plentiful dogs roaming around, friendly and happy to receive a handout and a pat on the head.

One does not simply go to Chile and not try the local foods. I happen to love tamales, and they had them, and with llama! Delicious.

Llama Tamales

When in San Pedro: Try the Llama Tamales! They are delicious!

San Pedro is the nearest large town to ALMA. It is a good drive out through the desert to the site. ALMA itself has two main locations, or bases of operation: the “Low Site” and the “High Site”. Altitude makes a lot of difference to human activity! The low site is the Operations Support Facility, the OSF, at an altitude of 2900m. The high site is the Array Operations Site (AOS) and is much higher: 5058m which just takes one’s breath away!

Atacama drive

Driving between San Pedro and ALMA gives an opportunity to see just how lonely it can be here in the Atacama. Not much plant life out there!

Distant volcanoes

Continuing on the drive, the desert offers views of distant volcanoes.

A llama!

A llama! This fellow (fella?) was just wandering around out there. We had no idea what it was able to find for food or drink, but he was owned: there was a little tag on its ear.

Entrance to ALMA requires a few checks:  One has to stop at the entrance gate for some basic safety training, a short safety video and identification with the guards. The view from the main road, Route 23, is pretty spectacular. Volcanoes stretch across the horizon, and they are still geologically active.

Distant geology at ALMA

While stopped at the ALMA entrance gate for checkin and training, the geology was just amazing to sort out! The peaks of these two volcanoes are on the Chile-Bolivia border.

ALMA Low Site Distant

In the distance, the ALMA low site where operations and maintenance take place.

ALMA Low Site

This is what telephotos are for: This is the ALMA Low Site.

Driving to ALMA Low Site

Driving from the entrance gate to the ALMA Low Site: safety is a major concern. There are radio telephones every so many kilometers. The Low Site is visible on the right side of this frame.

Active volcano

An active volcano just off the site!

Once at the low site, there is the constant safety reminder in plain site: UV radiation here and at the high site is usually at the “Extreme” level resulting in terrible sun burns should one not take precautions. I used SPF110 and was ready with hats. In the winter, as when we were there, it is a bit easier to be cautious with UV, as it gets cold up there! Not much skin is exposed.

UV Meter

A UV sunlight meter: safety at ALMA even takes into account the extreme climate’s exposure to UV radiation from the sun. The light never left the blue while we were visiting. SPF110 anyone?

Frigid visits ALMA

Frigid (the penguin) makes his first visit to ALMA, and he needed a lot of sunscreen!

The operations center has the needed controls for operating the whole array. There are basic status boards and controls for every necessary activity on site. Safety demands that people only work at the high site for 4 hours before needing to return to lower altitudes to give their bodies a rest. We were quite happy to have been at Cerro Tololo only days before: that helped a lot with acclimatization.

ALMA control room

ALMA: the low site control room.

ALMA status board

ALMA: The operations schedule and status for the antennae.

Outside at the high site, the antennae were arranged closely together. They are moveable with array sizes ranging from 150m to 14km.

The antennae at the high site.

The antennae at the high site.

Maintenance at the high site is an ever-ongoing process. Technicians are able to be at the site for 4 hours before needing to return to lower altitudes. The antennae need great attention, as they are very sensitive devices. Each is cooled by Helium, powered and placed in precise locations for operations. Keeping all this going in a land that is dusty, windy and experiencing temperature extremes is a big challenge!

ALMA antenna getting some maintenance.

ALMA antenna getting some maintenance.

Antennae below are a little further away from the array’s central cluster on this day. In the background one of the many volcanoes that make the whole area.

Distant antennae and volcanic backdrop.

Distant antennae and volcanic backdrop.

There are two different antenna sizes at ALMA: 12m and 7m.  They receive photons through the <remaining> atmospheric windows between 350 μm and 10 mm. Resolution depends on the array’s configuration, as the whole system operates as an interferometer. They have gotten to 10 milliarseconds, which is a huge accomplishment, as this is 5 times better than the Hubble Space Telescope’s ability, and ten times better than the Very Large Array’s ability.

The author braving the chilly winds and extreme UV at the high site.

The author braving the chilly winds and extreme UV at the high site.

The antennae in the central grouping on this fine, clear day.

The antennae in the central grouping on this fine, clear day.

Safety is a huge issue for ALMA and those that work there. We carried portable cans of Oxygen for a sip here and there. Let me be the first to tell you just how good it felt to get re-oxygenated once levels in the blood got to the mid-70% range. Low levels bring a person to hypoxia, something I am no stranger to as a pilot…. but one of the great equalizers of hypoxia is a general sense that all things are good, great in fact… illusory euphoria. Nice! Having 90% blood Oxygen is good, and it was easy with a quick shot or two from the cans.

This was posed, but still, the need to have some portable Oxygen was really there! We liked those little cans.

This was posed, but still, the need to have some portable Oxygen was really there! We liked those little cans. 😉

Portable blood Oxygen meter. Simply place it on a healthy finger and within seconds a reading is given.

Portable blood Oxygen meter. Simply place it on a healthy finger and within seconds a reading is given. This reading of 79% and heartbeat of 86BPM is indicative of a need to sip some Oxygen from the can.

Getting to a higher point on the plateau, one could see the entire array the day we were there. There was a light amount of snow also present, which was rapidly sublimating away into the very dry desert air.

Does this look like Mars to you? It sure does to me! Not a sign of living things other than those antennae over there!

Does this look like Mars to you? It sure does to me! Not a sign of living things other than those antennae over there!

There is a huge level of technical know-how going on behind the scenes at ALMA. All the antennae have FDDI feeds (fiber optics) to the central processing unit, “The Correlator”. When using many antennae, photons from their object of study arrive at very slightly differing times at each antenna. This is simply a matter of geometry. Photons from one source arrive at the closest antenna first, and hit the most distant antenna last. All this received data has to be aligned temporally before it can be analyzed scientifically. This is the job of the supercomputer called a correlator. The one at ALMA resides at the high site and has the equivalent of 134 million processors… some 20 million solder joints!  That is a lot of power.

The incoming fiber optic lines from the array.

The incoming fiber optic lines from the array.

The author besides one of the many rows of correlator's stacks of circuitry.

The author besides one of the many rows of correlator’s stacks of circuitry. The room hums with fans to keep the whole place at the proper temperature and humidity.

As noted earlier, each of the antennae are moveable, and with some incredible precision. Getting this done is no easy task. A specially designed and built transporter “truck” was designed and constructed just for this task. As an antenna is built and tested, it then must go up the path from the low site to the high site. This beast of a machine gets that done with the aid of very skillful drivers. The transporter has 14 independently steerable (and fully adjustable in height!) wheels, each of which is also independently powered. Ok!  A 14-wheel drive vehicle!  This machine lifts an antenna into a well-held mount and powers both itself and the antenna using two large diesel generators. The antenna must remain powered at all times: remember that it is cooled with compressed, super cold liquid Helium! There are two transporters, named Otto and Lore, and the best part? They can be controlled using a hand held remote control unit.

One of the two antenna transporters.

One of the two antenna transporters.

Local life on the ALMA road.

The auto road from the high site to the low site. This is one of the fauna living wild up there in the Atacama. At lower altitudes there is some scrub brush for them to eat.

One nifty little techy trick is that the iPhone (and many others) have built in GPS and compasses which imbed geo0location metadata into your photos. Here’s the array seen from inside the high site operations center. Yes, that is 16,500 feet.

vert_angle_deg=-4.8 / horiz_angle_deg=-0.2

Imbedded metadata for the photograph while at the high site.

vert_angle_deg=2.6 / horiz_angle_deg=0.2

The sky is so blue!  The air, so thin!

It was very windy and cold out there that day: little worry for a sun burn given that we were so bundled up in June, a.k.a. winter in the southern hemisphere. Frigid had a good time!

The author with Frigid, his beloved traveling companion.

The author with Frigid, his beloved traveling companion.

Coming off the high site and back into the Atacama Desert: not a whole lot of much going on out there.

Coming off the high site and back into the Atacama Desert: not a whole lot of much going on out there. I did want to get a soil sample and test it out for extremophilic bacteria.

If you happen to be visiting the ALMA sites, you are also near one of the most interesting places in the Atacama, the Los Flamencos National Reserve. Yes, there is water out there, but it is VERY salty!  Two large salt flats reside at the high altitude plateau in the Atacama: the Tara and the Aguas Calientes. The salt is pushed up out of the earth by hot springs. As the water evaporates it leaves behind fascinating crystal formations right on the surface of the desert… stretching for miles.

Salt flats in Los Flamencos, along with a volcano and a moonrise!

Salt flats in Los Flamencos, along with a volcano and a moonrise!

It would not be Los Flamencos without a…. flamingos! This particular species is the James flamingo and they just love to eat the brine shrimp that reside in the salty waters. Shrimp? Yep!

A James Flamingo enjoying the hunt for brine shrimp meals.

A James Flamingo enjoying the hunt for brine shrimp meals.

The ALMA trip is a wrap!

ACEAP2016 Group

The ACEAP 2016 Team. Back row, left to right: Charles Blue, Bill Bogardus, John Blackwell, Carmen Pantoja,  Sergio Cabezon, Derrick Pitts, Josh Roberts, Sian Proctor. Front row, left to right: David Lockett, Geneviève de Messière, Michelle Peterson. Photo: T. Spuck (AUI/NSF), not pictured.

More about The Astronomy in Chile Educator Ambassadors Program (ACEAP), please visit their pages at the National Radio Astronomy Observatory website here: ACEAP.

About johnb

- Director of Grainger Observatory, Phillips Exeter Academy. - Variable-star-crazed astronomer, but have done research in other areas. - Drummer, archer, pilot, chef, friend, pet owner, husband, father, Train-nut.
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One Response to San Pedro de Atacama and ALMA

  1. Hugh MacDonald says:

    John I finally looked at your pictures from Atacama! Beautiful! Hugh

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