This will be the first post in the category of 'Science in the modern world'. The science field of astronomy (as opposed to the lore of astrology; more on that in a future blog-post) has been a constant thread throughout my life so far. I will be describing my professional stories more or less in sequence, and will start with my early pre-professional years. One could call it a memoire or a sentimental journey. I will explain concepts and techniques for astronomical observations along the way.
Ever since I became a teenager the stars have put a spell on me, it seems. Reading popular books on astronomy have taught me the big picture and humanity's insignificant place in the vast, all-encompassing universe. And the realisation that the un-aided eye is only able to see a minute part of it, from the vantage point of our solar system, brought a deep sense of awe. Using simple means available to me I observed what little of this universe was accessible. The Moon, Sun, planets were initial targets, and later stars, Milky Way and galaxies. Having the ambition to let others share in my passion I co-founded a public observatory, open to all who wanted to see for themselves and learn.
After my studies I ended up working for the prime observatory in The Netherlands, nowadays named ASTRON, as an electronic development engineer. The observations by its telescopes are carried out at radio-wavelengths and for that reason the science discipline is called radio-astronomy. So instead of visible light we use radio waves; the only difference between the two is the wavelength of the electromagnetic radiation. The wavelength for visible light ranges from about 400 nanometer (violet) to 700 nanometer (red), and 1 nanometer is a 1 millionth of a millimeter, so a very small wavelength indeed. For radio-waves observed by radio telescopes based on Earth the range is between 0.3 millimeter and 300 meter.
The illustration shows where observations of light and radio-waves are done in the spectrum. One needs to understand that the conditions on Earth prohibit observing the other parts of the spectrum, because the atmosphere and ionosphere are largely opaque for these wavelengths. For that reason observations of infrared, UV, X and Gamma-rays have to be carried out from satellites in space.
At my position at ASTRON I designed equipment required for observing with the telescopes operated by the institute. For that to do successfully an understanding of astronomy and physics is very helpful, so I found satisfaction in combining electronics and astronomy. Furthermore, engagement with astronomers enriched my understanding of cosmology - the evolution of the universe from first beginnings to the present era - and the underlying physical processes that have shaped the universe, and all that is in it, from elementary particles, atoms and molecules, to planets, stars, galaxies and the large scale structures that permeate the universe.
The picture above shows some of the 14 telescopes of ASTRON's Westerbork Synthesis Radio Telescope, disappearing into the distance. For a long time in my career my job was to design instruments for this famous telescope. I'd like to think that some of the discoveries made were helped by my work, but of course I realise that if I hadn't been there somebody else would have been. Under ASTRON's umbrella I also worked on instrumentation for institutes elsewhere in the world. A wonderful project for the James Clerk Maxwell (JCMT) telescope, on top of Mauna Kea on the Big Island of Hawaii, led to the fortunate circumstance of working and living there, in the beginning of the 90'ies.
Mauna Kea is an inactive volcano with a height of 4207 meters above sea-level. Three radio-telescopes have been built there to profit from excellent conditions to observe from far above the altitude levels of high moisture content in the atmosphere, thereby allowing very short wavelengths in the radio spectrum. The third telescope was the Caltech Sub-millimeter Observatory (CSO, now decommissioned). Our instrument allowed us, for the fist time, to combine the signals from all three telescopes to yield unprecedented resolution - sharpness of the objects that were observed, using a principle called Very Long Baseline Interferometry (VLBI). This cleared the field for other millimeter-wavelength telescopes in in the world to participate in VLBI networks..
As an aside, the importance of observing objects at different wavelengths lies in the fact that processes in the universe manifest themselves at different wavelengths. For example, a particular transition in the hydrogen atom emits a photon with a wavelength of 21 centimeters. This is key to finding out the distribution of this most abundant atom in the universe. Observing this radiation at longer wavelengths allows us to determine the recession speed of the hydrogen atoms relative to us on Earth. This is due to the famous Doppler-effect. And in turn that allows us to come up with theories about the expansion of the universe, where everything is moving away from us - with a few 'nearby' exceptions where the object is moving towards us, as evidenced by a shorter observed wavelength than that of the typical wavelength at rest. Other species of atoms (and molecules) have their similar characteristic wavelength, elsewhere in the electromagnetic spectrum, including light. And that gives us a breakdown of the element composition in objects. There are physical processes that cause radiation to be emitted over a broad range of wavelengths as well. For example free moving electrons get deflected by magnetic fields and thereby emit radiation at radio-wavelengths. This allows us to study those magnetic fields, for example within our galaxy - the Milky Way. But the most simple physics mechanism is thermal radiation: any object in the universe with a temperature higher than absolute zero (0 degrees Kelvin = -273.15 degrees Celcius) will lose some of its energy by emitting a particular spectrum of electromagnetic (so-called black-body) radiation. The peak in intensity occurs at a wavelength related to the temperature of the object. For the Sun that is about 5600 degrees Celcius and corresponds to white light. For an object at room temperature the peak is at the longer infrared wavelengths. For even colder objects the wavelength becomes longer and longer until the peak will be in the radio spectrum. For that reason some radio astronomical observations aim to learn about cold gas clouds in the universe.
Throughout my career the topic interference by manmade radio emissions required my attention. When we want to observe the exceedingly weak radio signals from celestial objects the relatively strong signals coming from intentional transmitters (such as radio, tv, radar, mobile phones and satellites) drown out the celestial signals we want to observe. In addition, there is the interference coming from unintended sources, like the numerous pieces of electrical equipment such as appliances, tools, and the devices we design ourselves to do the observations. I have served on committees that address this problem by taking stock of the current and future situation, to educate engineers and bring awareness and a sense of urgency to legislating authorities. I have lectured on this topic in various parts of the world.
Now enter the SKA: Square Kilometre Array. The idea of building a new, large radio-telescope achieving unprecedented levels of sensitivity to open up the farthest reaches of the observable universe, gained critical support in the early 2000's. In view of the threats of radio-interference this new telescope must be located in a remote area, far away from transmitters and populated areas. A multi-national consortium was created and was given the task to do preliminary studies on telescope design and find the best location for it on Earth. Still working at ASTRON at the time I was given the assignment to investigate the radio-interference situation at sites proposed by four candidate countries. A receiver system was designed and built, that got deployed for about a month at each of those candidate sites: South Africa, China, Australia and Argentina. The results of that survey were that South Africa and Western Australia remained as candidate sites. And these short-listed sites were to provide all the necessary data to come to a well balanced decision on where to host the SKA. That included a new survey of radio-interference, which I supervised, seconded by ASTRON to the SKA Office in Manchester, England. In addition there was the need to generate and collect from the candidates all relevant information on the ins-and-outs of both locations in my capacity as chief site engineer. As a result I had been travelling around the world for this project between 2005 and 2012. While doing that I took the opportunity to combine my passion for photography and eagerness to meet and learn about cultures in the various countries I visited. The photographic harvest from these trips found their way into a book I self-published, along with some background on the sites and on radio-astronomy telescopes. Here's a link to that book.
Ultimately the decision was taken to grant hosting rights to both countries: South Africa for intermediate wavelength observing and Western Australia for the long wavelengths. So the SKA was split up along the line of observing wavelengths. South Africa had already been on a mission to construct a a precursor telescope, which is named Meerkat. Consisting of 64 telescope dishes it was completed around 2020 and was a resounding success, providing very sensitive observations in great detail. Meerkat will ultimately be integrated into the SKA, which currently is being constructed in both countries. Meerkat plus the SKA will then be the most powerful radio-telescope in the world for years to come.
In 2015 I moved to South Africa to start working for the South African Radio Astronomy Observatory (SARAO). Mostly in an advisory role on topics like instrumentation and dealing with radio-interference. To this day (2024) I have kept working as a consultant, ever since retiring from ASTRON and SARAO.
I now have more time to spend on enjoying life here. This is a magnificent environment to deploy my usual passions and some new ones. New chapters in the book of life.
Rob Millenaar
Except where indicated, all photos in this post were taken by me. ©2024 Rob Millenaar
Creating new chapters in the book of life is a wonderful privilege.