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About the Author
Sarah Wild is the science and technology editor for Business Day. She is a former features editor with the Sunday Times Magazine and has been honored with a Siemens Profile merit award.
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Searching African Skies
By Sarah Wild
Jacana Media (Pty) LtdCopyright © 2012 Sarah Wild
All rights reserved.
What is radio astronomy?
It is 1931, and an American radio engineer sits in front of reams of paper, wondering if he is losing his mind, if there is something wrong with his instruments, or both. He adjusts his glasses and runs a hand over his prematurely balding head. On paper, his job is simple: find out what causes interference on transoceanic radio communications, specifically long-distance, short-wave communications. In real life, the task is somewhat more complicated.
Karl Jansky, an employee of the Bell Corporation, has isolated two aspects of the interference: nearby and distant thunderstorms. But there is something else. It plays through his instrumentation like a supersonic tinnitus, a static that is sometimes there, sometimes not.
He has built an antenna to measure radio waves of 20.5 MHz, rotating on four Ford Model-T tyres. That way, he can find this mysterious source of static, which seems to radiate from all directions.
If you have an image of a super-slinky, sexy, rotating apparatus, its slicked chrome-and-ceramic veneer dreamily spinning like something out of 2001: A Space Odyssey, forget about it. This is the 1930s. Commonly called "Jansky's merry-go-round", it is a leviathan, even in its own time. Thirty-five-and-a-half metres in length, the radio-wave receiver is a series of enormous cross bars and square metal frames, and takes 20 minutes to complete a 360-degree rotation.
Close to the device, Jansky sits in a separate shed, staring at the data from his analogue pen-and-paper machine. It's there – a variable hiss that peaks once a day.
Five hundred years ago, people thought that the universe – in which the Earth was the prestigious centrepiece – comprised enormous spheres, moving together in mathematical harmony. Musica Universalis, the music of the spheres, was ancient philosophy, rather than actual music.
While most scholars dealt with this on a metaphysical level, Johannes Kepler – whose laws of planetary motion describe the elliptical orbits of planets around the Sun – believed that they really made music, singing like half-filled wine glasses played with a moistened finger. A mixture of religion and science, these spheres sung the music of the heavens.
According to Kepler, celestial bodies orbited each other at a fixed distance, which corresponded to a specific pitch, in the same way that a string of a certain length on a violin elicits a certain note. All these notes were weaved into a pattern of proportion, a divine pattern that determined the universe.
Now, while Kepler was on the mark about the maths, he was a bit confused about the music.
Tangentially, while the ancients were wrong about a number of things, such as a Geocentric Earth and the health benefits of leeches, they were half right about the music of the spheres.
Initially, Jansky thought the static was originating from the Sun because of the undulating nature of the maximum intensity. But it didn't fit with the 24-hour solar day – with pure obtuseness, the signal repeated every 23 hours and 56 minutes, in sync with the sidereal day, which is measured via the Earth's rotation with respect to a fixed extrasolar object.
What Jansky had in fact stumbled upon was radio waves emitted by the Milky Way.
Now the 1930s were a tough time to find funding for large experimental science projects. The Great Depression had struck the world in the late 1920s and no one had money to spend, so – although Jansky published his findings in 1933 – the discovery lay dormant for a number of years.
He tried to convince Bell Laboratories to build an even bigger antenna, but experimental physics paled in comparison to the demands of a bottom line, and Jansky was redeployed within the company.
It took decades for scientists to discover that other celestial bodies emitted radio waves at other frequencies, but the invention of Jansky's merry-go-round formed the foundation of the new discipline we have come to know as radio astronomy. Stars, galaxies, pulsars, quasars – they all emit radio waves of different frequencies.
Traditional astronomy used, and still uses, optics to see into outer space, but the range of the visible spectrum – the seven colours that the human eye can see – forms only a tiny part of the electromagnetic spectrum. Radio waves occupy a large portion of the spectrum, which means that you can detect a greater variety of wave and can gain fresh insight into the universe. By collecting and collating the data from the different electromagnetic-radiation frequency bands, we are able to map out the dark recesses beyond the Earth, like blind cartographers listening to the sounds of the universe.CHAPTER 2
The origins of radio astronomy in South Africa
It's all America's fault. If Australia is looking for someone to blame for its Square Kilometre Array competition, it should blame the United States. The existence of radio astronomy as a discipline in South Africa is actually thanks to the United States' National Aeronautics and Space Administration (Nasa). Until the KAT-7 was built in the Karoo in 2010, the country's first and only radio astronomy observatory was once Nasa's Deep Space Station 51, nestled in the hills of Hartbeeshoek, Gauteng. It sounds like something out of a Cold War spy movie, or at least a science-fiction thriller involving aliens and Armageddon.
Well, it was the Cold War, and the Russians had fired the first Space Race salvo in 1957 by launching the satellite Sputnik 1 into space. In 1960, the then Union of South Africa's Council for Scientific and Industrial Research (CSIR) entered into an agreement with fledgling Nasa to host one of its Deep Space Stations in the country, to track American automated lunar and planetary probes.
Satellite and rocket launching is a risky business, and the spacecraft needs to be tracked throughout its launch. But if it's launched in the United States, the Americans don't have eyes on the other side of the world to watch its movements. So Nasa's Jet Propulsion Laboratory established three Deep Space Stations, one in South Africa, and another two in California and Australia. The stations were approximately 120 degrees apart in longitude and effectively divided the Earth's rotation into thirds, providing continuous and overlapping coverage.
Not to sound esoteric, but planetary motion also played a role in the establishment of tracking stations in the Southern Hemisphere. In the 1960s, the inner planets out to Mars all had southerly declinations, which meant that if a probe was sent to Mars, it would remain very far south for months at a time. As a result, it was only possible to continuously track spacecraft – and sometimes Mars – by having a station in South Africa rather than Europe. The Southern Hemisphere doesn't permanently have this natural advantage over the north. Planetary declinations are cyclical. Through a confluence of circumstances – lucky circumstances for South Africa – the planets were favouring Southern Hemisphere observation during the 1960s and early 1970s.
Without Nasa's involvement, it is unlikely South Africa would have had a radio astronomy programme at all. At the very least, the country wouldn't be as advanced in this field as it is today.
The people holding the purse strings in the late 1950s thought that Australia was too far advanced in radio astronomy for South Africa to be truly competitive. It is also worth noting that, just as it is today, radio astronomy is a rather expensive field to be involved in.
Australia's competitiveness dates back to the post-Second World War period. Both South Africa and Australia were building radar systems because, as Commonwealth countries, they had developed radar in conjunction with radar specialists in the United Kingdom to defend their respective coastlines against attack. Radar, short for radio detection and ranging, works by bouncing radio waves off objects to determine their location, direction and speed, and you need both a radio transmitter and a receiver.
Radio astronomy uses similar techniques, except that it doesn't need a transmitter. Celestial objects, which generate a wide variety of natural radio signals, are the transmitters, and the receivers need to operate across a range of frequencies.
After the Second World War, there was a surplus of radar equipment and a surprising discovery had thrust Karl Jansky's cosmic radio waves into the spotlight. British physicist James Stephen Hey had been tasked with devising radar anti-jamming methods during the war. In February 1942, he received reports of severe noise interfering with the Allies' anti-aircraft radars. At first, he thought it was caused by crafty radar-jamming techniques or interference by German forces, but after some discussion with the Royal Society of London for Improving Natural Knowledge, he realised it was radiation from the Sun. But because it was wartime and "keeping mum" was the order of the day, Hey was not allowed to publish his discovery until after the war.
In this post-war period, Australia got an impressive head start in radio astronomy. The country had a number of radar specialists, and unlike countries such as the United Kingdom and the Netherlands, there was little organised academic research. While this might sound like something that might hold back academic inquiry, it isn't. It meant that people with radar skills who were interested in radio astronomy could just start tackling research problems, without it having to be coordinated into university groups and limping through an obstacle course of academic bureaucracy.
If you have a discussion with anyone in South Africa's radio astronomy community about the history of the discipline, they will tell you to speak to George. Or else they will start telling you stories, and interspersing them with comments such as, "You need to check with George about the dates. He'll remember" or "George has a good memory for how things went forward".
So when you finally meet Dr George Nicolson, he is a bit of a surprise. The grandfather of South African astronomy – who was the first employee at Nasa's deep space tracking station and the Hartebeesthoek Radio Astronomy Observatory's (HartRAO) first director – has a shock of white hair, blue eyes that twinkle as brightly as the stars he's spent his life looking at, and a mischievous smile.
The reason people will direct you to Dr Nicolson is because he was there, he lived the early days of radio astronomy. So, when asked about Australia's prowess at that time, he is unequivocal: "They were undoubtedly world leaders, in terms of publications, number of people they had working in radio astronomy and the quality of work that they were doing."
Because of this, the first president of the CSIR, Dr Basil Schonland – who also led the development of South Africa's radar system – believed the country had no chance of catching up with Australia, and should instead concentrate on something that was unique to South Africa, such as using radar to study lightning because the country has such a high incidence of the phenomenon.
Nasa's Deep Space Station 51, however, removed the impediments of funding and Australia's competitiveness. The constrained budget was no longer an issue because Nasa was bankrolling the infrastructure. And, in the Space Race, US pride was on the line, so money didn't seem too difficult to come by. The space agency built a 26-metre dish in Hartbeeshoek's verdant hills, far away from possible interference. It operated in the 960 MHz frequency range, designed for signals with a wavelength of about 30 centimetres. The only way to get there, from either Pretoria or Johannesburg, was along dirt roads.
Concurrently, Rhodes University in Grahamstown had started its own mini radio astronomy programme, by using conventional shortwave communications receivers and low-cost high-frequency wire antennas, which further diluted the cost threat of the country becoming involved in radio astronomy.
Nasa provided the skeleton for radio astronomy in South Africa, and it was literally a skeleton. What now appears to be a handsome parabolic dish comprised, in those days, a seemingly flimsy wire mesh surface. "When you looked at the dish, you just looked straight through it," Dr Nicolson says. "It was quite a spidery structure and it went through various upgrades over the years."
But, in an example of why you shouldn't judge a book by its cover, that "spidery" telescope also housed state-of-the-art Nasa technology. The deal brokered between Nasa and the CSIR – the council's National Institute for Telecommunications Research in Johannesburg was responsible for the tracking station – stated that as long as it didn't disrupt the dish's primary tracking function and duties, the dish could be used for radio astronomy.
Not that there were many people who could use it for radio astronomy – there was only Dr Nicolson. He had originally worked for the CSIR, but was transferred to the Hartebeesthoek facility as "basically their first employee".
"The one thing the director of our institute [Dr Frank Hewitt] impressed on me right from the beginning was that it was going to be a one-man programme. He said that I had to be careful to choose projects that people with greater resources couldn't complete in a shorter period of time," Dr Nicolson says.
So, as part of his MSc degree, he began a survey of the Southern Galactic plane at 960 MHz. "So I initially started off by completing the survey of the southern Milky Way galaxy, preparing for it in 1961, building the equipment in 1962 and carrying out and analysing all the observations in 1963." A more extensive survey had been undertaken by the Owens Valley Radio Observatory in California, but because of its geographic location, observations from the Southern Hemisphere were needed to fill in gaps.
Back then, in 1961, radio astronomy was worlds away from what it is now. These days it is such a complex discipline that niche specialities have developed: data management, computer interfacing, data analysis, telescope construction, receiver technologies.
Dr Nicolson takes a moment to think, before commenting on the differences between nascent and modern radio astronomy. "In the earlier days of radio astronomy, people had to have a range of skills. They were mostly physicists or engineers rather than astronomers, so they had to learn astronomy along the way. As radio astronomy developed, people became less dependent on having technical skills to do radio astronomy. Today, most of the world's radio astronomers know very little about the technical details. They rely on the engineers and those astronomers who have technical knowledge and who have developed systems to provide them with a working instrument. They just get the data that streams out."
These days, radio astronomy comprises a large number of specialists, who work in niches to synthesise this complex beast. Back in the 1960s, radio astronomers built their own instruments, and if something didn't work they had to fix it.
Aside from the fact that Nasa provided the 26-metre dish, there were other definite benefits to being affiliated with an organisation that was trying to one-up its Russian competitors. For one thing, the relationship brought with it the most cutting- edge and sensitive gadgets available.
In 1964, Deep Space Station 51 changed its operating frequency from 960 MHz to 2290 MHz. While Nasa did this to improve its tracking capability, South Africa got caught in the slipstream of four-times-more sensitive equipment. The amplifier Nasa installed gave the country's radio astronomy community proportional advantage because it made the dish more sensitive in some respects than any other radio telescope in the world operating at that frequency range.
However, the receiver on the telescope also needed a facelift and a new noise-adding radiometer, which – through necessity because there wasn't really anyone else to do the job – was built by Dr Nicolson.
With a new operating frequency and machinery so advanced it should have worn a space suit and had a spacecraft powered by cold fusion, the lone radio astronomer/engineer needed a new project. So Dr Nicolson decided to observe quasars, which had recently been discovered. A quasar, otherwise known as a quasi-stellar radio source, is a region at the centre of a galaxy, usually a very young galaxy, and is one of the most luminous and energetic objects in the universe. Scientists believe that it surrounds a supermassive black hole that is so dense and has such a strong gravitational pull that not even light can escape it. Quasars can be up to 100 times brighter than an entire galaxy, brighter than all the Milky Way's stars packed into a small region.
Excerpted from Searching African Skies by Sarah Wild. Copyright © 2012 Sarah Wild. Excerpted by permission of Jacana Media (Pty) Ltd.
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Table of Contents
Chapter 1 What is radio astronomy?,
Chapter 2 The origins of radio astronomy in South Africa,
Chapter 3 The history of astronomy in South Africa,
Chapter 4 Southern African Large Telescope,
Chapter 5 Back to basics,
Chapter 6 The KAT-7 and the MeerKAT,
Chapter 7 African SKA,
Chapter 8 Challenges,
Chapter 9 The African VLBI Network,
Chapter 10 Benefits,
Chapter 11 SKA science,
Chapter 12 Looking to the future,