From ESOblog (EU): “A day in the life of an ALMA astronomer” 

From ESOblog (EU)


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European Southern Observatory [Observatoire européen austral][Europäische Südsternwarte] (EU) (CL)

22 October 2021

Marie-Lou Gendron-Marsolais

Marie-Lou Gendron-Marsolais is an ESO fellow with duties at Alma since October 2018. She obtained her PhD in 2018 at The University of Montréal [Université de Montréal](CA) under the supervision of Julie Hlavacek-Larrondo. She now shares her time between her work for ALMA and the study of galaxy clusters. Her research focuses on the complex relation between supermassive black holes located at the center of galaxies and their environment.

ALMA, the Atacama Large Millimeter/submillimeter Array [below], is an ensemble of 66 antennas that observe the cold dark universe from the remote Chajnantor Plateau in the Chilean Atacama Desert. The antennas work together as a single kilometre-sized telescope, giving us unique insights on all sorts of cosmic objects, from planet nurseries to the very first galaxies. But how is it like to operate such a complex machine? Marie-Lou Gendron-Marsolais, an ESO Fellow in Chile, has given us an exclusive behind-the-scenes look at a day in the life of an ALMA astronomer.

It is 6:30 am and the crisp cold air would wake up even the most sleepy astronomer. On the short walk from my home to the ALMA office along the deserted streets of Santiago, the sky is still completely dark and I look up to see if some bright stars are piercing the light pollution of the megalopolis. The moon is accompanied by Jupiter and Saturn, offering a surprisingly harmonious spectacle that makes me smile.

Most people think that astronomy is a science exclusively done by night, but it is not the case for many telescopes. It all depends on the light you are looking for! There is much more light than just the colours of the rainbow and, with specific types of telescope, this “invisible light” is accessible. In the case of ALMA, we collect “radio” light. Since the Sun does not emit much radio light and our atmosphere does not diffuse it, the radio sky is not too bright during the day and we can observe with ALMA any time of the day. Therefore, astronomers are not necessarily night creatures…

This aerial picture shows the Chajnantor Plateau, place of the ALMA Observatory, from high above. Dozens of dishes from the Observatory are spread over the plateau and cast long dark shadows in the red sand. In the centre of the image the crowded gathering of the Atacama Compact Array is visible. Credit: A. Marinkovic/X-Cam/ ALMA (ESO/NAOJ/NRAO.

The global pandemic situation has hit ALMA operations hard, forcing us to completely shut down the site for many months. Since then, the devoted work of technicians and engineers has allowed us to restart nearly all of our cherished antennas and start observing again, a daunting task! The observatory is located 1200 km north of Santiago. To reduce the amount of travelling and the number of people on site, we, astronomers, are now observing mostly from Santiago, in our new remote control room.

At the ALMA headquarters, I am welcomed by Jose Miguel, Data Analyst, who has spent the whole night observing. “Perfect weather up there!”, he says, before discussing with me some additional technical details on the work accomplished and the state of the telescope. I wish him a good “descanso” as this is his last night and a new team is taking over today.

After the disinfection of the control room, I take seat in the familiar decor, greeted through videoconference by Hector, Array Operator Deputy Manager, in the room across the corridor, and Ludwig, Array Operator, at the Operations Support Facility up in the desert, just 30 km away from the antennas themselves.

Despite the fatigue and the fact that I haven’t stepped foot in this room for several weeks, my eyes sweep across the four control screens full of different tools, plots and scrolling terminals, and almost instantaneously everything comes back. It is a bit like riding a bike — you just never forget how to do it! But perhaps it has to do with the fact that I have spent more than 600 hours here in the last 2 and a half years! And still, each time, I learn new things. ALMA is a very complex machine.

Ludwig, who’s in charge of keeping the antennas in good condition, guides me through the plan of the day as he will leave the site in a couple of hours after a complicated shift. I know very well from experience that living more than a week at 3000 metres above sea level in the harsh weather of the Atacama Desert is far from relaxing. Last night, the temperature dropped to -15 ºC, and in the last 2 weeks ALMA has been hit by severe snowstorms and high winds. It took days for the team to clear the snow and recover the telescopes…

But the weather now is incredible. Our weather stations constantly measure the amount of water vapour above the antennas, which is currently exceptionally low. The extreme dryness of the air is what makes the Chajnantor plateau ideal for radio astronomy — it is absolutely essential since water in the atmosphere will absorb the light we are trying to collect. I wish Ludwig a safe trip home.

Marie-Lou observing remotely at the ALMA office in Santiago. Note that due to COVID restrictions there is never more than one person in the control room; they operate one at a time. Credit: M. L. Gendron-Marsolais.

Today, the engineers have not requested to work on the antennas, so we have the go ahead for a whole day of scientific observations. It is hard to tell from here, but about a hundred engineers work everyday at the site, making sure our 66 antennas are performing at their very best. My job, as an astronomer, is the very last step of a long chain of complex tasks accomplished by dozens of people –– this is how we run ALMA.

The voice alarm of my console announces the beginning of the observation project I just scheduled: “Array-81, started”. It is always very rewarding to think that soon, somewhere around the world, the astronomers in charge of this project will receive their precious data, analyse them, and eventually make their contribution to our understanding of the Universe.

A cup of coffee in hand, I schedule projects depending on the elevation of the targets in the sky, the stability of the weather, the scientific priority of the project, etc., optimising every minute of ALMA time. From galaxies with intense star formation to young nearby stars, the observations we carry out vary greatly. The science that can be done with ALMA covers a wide variety of subjects, from our own Solar System up to the most distant galaxies.

During our daily 3pm online meeting, I report on the projects observed, the weather conditions and the various problems encountered in the last 24h to the program management group. After some discussion, tasks are allocated and we agree on a plan for the next day.

Focused on the evolution of the last observations taken, I am surprised by the smiling Satoko, a science operations astronomer, softly knocking on the door. The last 8 hours have passed very quickly! Since ALMA can observe day and night, astronomers work on three 8-hour-long shifts and mine is now over. It is now time to pass over the control to my colleague and take a well-deserved rest.

See the full article here .


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European Southern Observatory [Observatoire européen austral][Europäische Südsternwarte] (EU) is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

European Southern Observatory(EU) La Silla HELIOS (HARPS Experiment for Light Integrated Over the Sun).

ESO 3.6m telescope & HARPS atCerro LaSilla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

MPG Institute for Astronomy [Max-Planck-Institut für Astronomie](DE) 2.2 meter telescope at/European Southern Observatory(EU) Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU)La Silla Observatory 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) , Very Large Telescope at Cerro Paranal in the Atacama Desert •ANTU (UT1; The Sun ) •KUEYEN (UT2; The Moon ) •MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening star). Elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo.

European Southern Observatory(EU)VLTI Interferometer image, Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level, •ANTU (UT1; The Sun ),
•KUEYEN (UT2; The Moon ),
•MELIPAL (UT3; The Southern Cross ), and
•YEPUN (UT4; Venus – as evening.

ESO Very Large Telescope 4 lasers on Yepun (CL)

Glistening against the awesome backdrop of the night sky above ESO’s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT, a major asset of the Adaptive Optics system.

ESO/NTT NTT at Cerro La Silla , Chile, at an altitude of 2400 metres.

Part of ESO’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light, with an elevation of 2,635 metres (8,645 ft) above sea level.

European Southern Observatory/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

European Southern Observatory(EU) ELT 39 meter telescope to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

European Southern Observatory(EU)/MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) ESO’s Atacama Pathfinder Experiment(CL) high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

Leiden MASCARA instrument cabinet at Cerro La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft).

ESO Next Generation Transit Survey telescopes, an array of twelve robotic 20-centimetre telescopes at Cerro Paranal,(CL) 2,635 metres (8,645 ft) above sea level.

ESO Speculoos telescopes four 1 meter robotic telescopes at ESO Paranal Observatory 2635 metres 8645 ft above sea level.

TAROT telescope at Cerro LaSilla, 2,635 metres (8,645 ft) above sea level.

European Southern Observatory(EU) ExTrA telescopes at erro LaSilla at an altitude of 2400 metres.

A novel gamma ray telescope under construction on Mount Hopkins, Arizona. A large project known as the Čerenkov Telescope Array composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile at, ESO Cerro Paranal site The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the. University of Wisconsin–Madison and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev.

European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU), The new Test-Bed Telescope 2is housed inside the shiny white dome shown in this picture, at ESO’s LaSilla Facility in Chile. The telescope has now started operations and will assist its northern-hemisphere twin in protecting us from potentially hazardous, near-Earth objects.The domes of ESO’s 0.5 m and the Danish 0.5 m telescopes are visible in the background of this image.Part of the world-wide effort to scan and identify near-Earth objects, the European Space Agency’s Test-Bed Telescope 2 (TBT2), a technology demonstrator hosted at ESO’s La Silla Observatory in Chile, has now started operating. Working alongside its northern-hemisphere partner telescope, TBT2 will keep a close eye on the sky for asteroids that could pose a risk to Earth, testing hardware and software for a future telescope network.

European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU) The open dome of The black telescope structure of the‘s Test-Bed Telescope 2 peers out of its open dome in front of the rolling desert landscape. The telescope is located at ESO’s La Silla Observatory, which sits at a 2400 metre altitude in the Chilean Atacama desert.