This 500 meter behemoth will not only be the world’s largest radio telescope, but it will peer deeper into space than anything has done before.
The 500 m Aperture Spherical Telescope (FAST) – the world’s largest radio telescope – fills a vast, natural basin between mountains and hills in southwest China and, in doing so, looks like a real-life James Bond villain’s lair.
Perhaps the reference is influenced by the faint memory of a climactic scene in the film GoldenEye, when James Bond (Pierce Brosnan) and Natalya Simonova (Izabella Scorupco) find themselves being shot at and sliding down the bowl of another monstrous radio telescope – this time Puerto Rico’s Arecibo Observatory, which has a diameter of 305 m.
If the characters were to attempt the same stunt on the Chinese telescope, their slide would have been considerably longer – the FAST dish measures a massive 500 m across. Due for completion later in 2016, FAST began construction in 2011, although the concept dates back to 1994. The natural depression in which it nestles has a diameter of around 800 m. It is 170 km by road from provincial capital Guiyang in Guizhou Province.The structure taking shape.
“The location is a challenge, but it is a common challenge,” said Brian Middleton, vice-president ANZ of Bentley Systems, which provided the BIM technology behind the build.
“The vast majority of the major infrastructure projects in Australia, for instance, are becoming more challenging. Putting a railway line under the centre of Melbourne or Sydney is a challenge because of the impact of the environment in which you’re working. In oil and gas or mining, all of the easily accessible areas have been exploited, so we are pushing into areas where you don’t have the infrastructure or the engineering expertise at hand.”
What has been different about this project, thanks to the science behind a radio telescope, is the tremendous accuracy required and the sheer number of experts employed on the job.
“Because the telescope is a scientific instrument it needs to be extremely accurate,” Middleton said.
“Many of the components had tolerances of less than a millimetre, so we needed to apply the very best digital engineering technologies.”
The scope of the project to be managed is difficult to comprehend: more than 200 designers from four organisations working on a radio telescope measuring half a kilometre in diameter and with a tolerance of one millimetre.
In order to ensure they were working from current information at all times, the National Development and Reform Commission (funding the project) and the National Astronomical Observatories of Chinese Academy of Sciences (managing the build with the government of Guizhou province as a partner) brought Bentley Systems on board.
By using a range of software covering multi-discipline building design, modelling, issue resolution, project information management and cloud collaboration services, they created a BIM database and a standardised approach that Bentley believes saved hundreds of man-days of design modification, review and error handling.
“There are BIM maturity levels of zero, one, two and three. Zero is what most people do today – designing in 3D and publishing in 2D,” Middleton said.
“Level one is about 3D modelling and has been around for 15-20 years. With FAST we went beyond that – into BIM level two – within our collaborative software. Being able to share the information that you create in 3D models, as well as associated information, into a collaborative environment where you have one current and approved version of the design means integrity is maintained.”
Such a system, Middleton said, means intelligence created during the design and construction phase is not lost. Just as importantly, it is now made available for not just the remainder of the build, but also for the future life of the asset.
“We can update the information as changes are made to the assets over the next 20 to 30 years,” he explained.
“There will be replacements and upgrades and retrofits. By creating a common data environment you remove risk and error and it enables you to do clash detection in digital environments, which is a significantly lower cost than when you have to make a change in the physical environment.”
The centre of it all
Australia’s CSIRO was brought on board to construct the all-important receiver, the itemthat hangs at the focus of the dish and captures, amplifies and converts radio signals coming in from other galaxies.
The receiver is small enough to fit in one room, around 1.5 m in diameter and 2 m high. But it is packed with high technology. This is a 19-beam receiver, which enormously increases the efficiency of the entire radio telescope.
“The receiver essentially multiplies the capability of the telescope by 19,” said Dr Douglas Bock, Acting Director of CSIRO Astronomy and Space Science.
“A single beam receiver allows the telescope to look at one thing in the sky. It might measure hydrogen in the universe in one direction. The 19-beam receiver allows you to speed up the mapping of the sky whether you are looking at hydrogen, the most abundant element in the universe, or whether you are looking for pulsars, which are rapidly rotating remains of stars that have exploded.”A computer simulation of the dish’s receiver built by CSIRO.
Alex Dunning, an RF/microwave engineer with CSIRO, has spent much of the past 12 months putting the receiver together and said that while it is a tiny piece of the telescope, but it is vital.
“There are a few critical areas of a telescope, and the receiver is definitely one of them,” he said.
“In this build there have been a lot of innovations. For instance, because it is such a big system, there has been a lot of attention paid to the cryogenic design due to the thermal constraint.”
Critical parts of the ‘feed horns’ and amplifiers that receive the radio signals must be cooled down to below minus 200 degrees Celsius in order to increase their sensitivity. Astronomical signals are often extremely weak, so any ‘noise’ within the receiver will hide those signals. Cooling the feed horns and amplifiers reduces their thermal energy and therefore lowers their noise.
“They are cooled by three commercial cryogenic refrigerators,” Dunning said.
“But when you cool things down that much there is a lot of contraction. The mechanical constraints that come from contraction in such a big receiver can cause issues, so we have had to find ways around that.”
The majority of the receiver is made from aluminium, but some exotic materials such as indium, gold and pure, oxygen-free copper are also required for various purposes, including as thermal gaskets and heat conductors in cryogenic environments. Specific types of gallium arsenide devices are also required.
“Clearly the size of this antenna is a great thing,” said Dunning, who will travel to China later in 2016 in order to assist with the receiver’s installation.
“It is going to be the biggest antenna in the world and the most sensitive. There are all sorts of things that this telescope is going to be able to do that others will not. Being a part of the build of such a big telescope is a wonderful opportunity.”
But what’s it for?
Professor Naomi McClure-Griffiths from Australian National University’s Research School of Astronomy and Astrophysics at Canberra’s Mt Stromlo Observatory, discussed the value of a super-sized radio telescope
create: What is a radio telescope’s purpose?
Naomi McClure-Griffiths: They have multiple purposes. Radio telescopes are very good at looking at gas in galaxies, unlike optical telescopes that look at stars and planets. Radio telescopes also excel at identifying interesting and exciting objects such as pulsars.
create: Why is that important?
NMG: Our main objective is to understand how galaxies work. We don’t understand the most basic things. How does the gas come together and start forming stars? How does a galaxy evolve over the billions of years of its lifetime? And pulsars are perfect atomic clocks. By looking for small changes in that clock it tells us about the space that the radiation has travelled through. That gives us information about our own atmosphere, about the galaxy itself and about the nature of space and time.
create: And why is bigger better?
NMG: There are a lot of great things that will come from this telescope’s size. Once operational, it will be able to identify pulsars too weak to be seen with any other telescope.
create: Will the information from FAST be shared internationally?
NMG: A lot of radio telescopes operate under the Open Skies protocol, meaning anybody in the world can ask for time on that telescope. FAST will have open access, but each team of users will be required to have some Chinese members.
create: Do we have anything similar in Australia?
NMG: Our biggest telescope used for this kind of research is in Parkes. But a telescope that is 20 times bigger is a completely different ball game. Having said that, Parkes is in the southern hemisphere and is fully steerable so can see things you will not see with FAST.
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