Date: November 3, 2011
Title: ALMA: The Building Blocks of Something Great
Podcaster: Adam Avison
Organization: UK ALMA Regional Centre Node
Link: www.alma.ac.uk
Description: For around a month now the Atacama Large Millimetre/sub-mm Array (ALMA) has been carrying out its first scientific observations, but how does such a huge international collaboration ever come into being? Lets look at some of the pieces which bit by bit make a truly revolutionary telescope.
Bios: The UK ALMA Regional Centre Node forms one of the seven nodes which make up the EU ALMA Regional Centre, which provide support for ALMA science users throughout Europe.
Dr. Adam Avison is a postdoctoral research associate at the UK ARC Node based at the Jodrell Bank Centre for Astrophysics based at the University of Manchester.
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Transcript:
Hi, welcome to another episode of the 365 days of Astronomy Podcast, I am Adam Avison a postdoc at the UK ALMA Regional Centre Node based at the Jodrell Bank Centre for Astrophysics at the University of Manchester. For a little over a month now, the most complex ground based astronomical instrument ever built, the Atacama Large Millimeter/Sub millimeter Array or ALMA, has been up and running taking its first scientific observations. In this time ALMA has been observing at millimetre and sub-millimetre wavelengths using 16 of its eventual 66 individual dishes, high on the Chajnantor Plateau 5000m above sea level in the Atacama Desert.
ALMA uses a technique known as interferometry. This technique combines together the electromagnetic waves arriving from space at each dish to synthesizes the affect of having a single incredibly large telescope, much bigger you can possibly build a single structure. ALMA will eventually act like a single telescope 14km across, I mean can you imagine building a structure that big?
ALMA is being used by astronomers to observe at mm wavelengths allowing them to observe the chemical and dynamic properties of gas and dust within in our own galaxy. This material shows us the regions in which stars are beginning to form, right to the other end of the lifecycle of stars allowing us to see the energetic episode seen at the ends of a stars life.
Astronomers are also be able to observe the dust and chemical composition of galaxies other than our own, allowing us to peer back in time to very early periods in the lifetime of the Universe. All this with never before achieved resolutions and sensitivities.
But how does such a large and complex project like ALMA come into being?
As you can imagine, it takes a long time and a lot of people. Earlier this year I was at a conference where the speaker showed an NRAO memo written by Frazer Owen in 1982 entitled ‘the Concept of a millimeter Array’ which sowed the seeds of building a millimeter array. A concept which eventually became ALMA. Brilliantly the memo ends with the sentence ‘Obviously all is more complicated than the remarks given above; however, none of it seems impossible’
Over the intervening 29 years, the concept has proved to be possible and with the hard work and excellent contributions of astronomers and engineers throughout the world this concept has eventually become ALMA. Today ALMA is an international collaboration between Europe, North America and East Asia with the cooperation of the Republic of Chile. The three partners in ALMA are organized into ALMA Regional Centres or ARCs, whilst Chile hosts the Joint ALMA Office as well as the telescope itself. Each ARC has added its own contributions, smaller building blocks on the road to ALMA which have made it a truly cutting edge astronomical instrument.
So what form can these building blocks take? For examples of the kinds contributions each ARC and partner has made to the ALMA project we can look at some of those from the UK (seeing as that is where I am and therefore hopefully least likely to make a mistake!).
The UK has made both hardware and software contributions to the ALMA project.
On the hardware side, the prototype of ALMA’s unique water vapour radiometer (WVR) system was developed by Cambridge University in
collaboration with Onsala Space Observatory in Sweden. The WVR system is designed to correct the rapid phase errors, similar to the effect known as ‘seeing’ in an optical telescope, caused by atmospheric turbulence. This is crucial for getting the best quality images out of the ALMA telescope.
The fibre optic system that connects all the ALMA’s telescopes to its central computer system (known as the correlator) was developed at the Jodrell Bank Observatory at the University of Manchester, which the digital components being provided by the National Radio Astronomy Observatory in US and additional optical cable management work from the University of Kent. This system allows each telescope to output 10 gigabits per second and 120 giga bits per second to be transmitted over 20km distances to the correlator. I really wish my internet connection at home was this fast.
On the software side, The UK Astronomy Technology Centre based in Edinburgh in collaboration with European Southern Observatory and National Astronomical Observatory of Japan, has developed the Observing Tool, the piece of software used by the astronomy community to plan and propose their ALMA observations. It provides ALMA users of varying levels of observing expertise an interface to configure and visualize the more technical side of their intended observing program.
Another software based contribution is the Observation Support Tool (or OST), one of the two ALMA simulators available to astronomers. The OST was developed at Oxford University and hosted and maintained at the University of Manchester. The OST provides a simple web form from which a potential ALMA astronomer can simulate what kind of an image ALMA would return given a particular telescope setup.
Of course these are just examples from the UK and there are countless contributions from all parts of the ALMA collaboration. Things like the huge software suite, known as CASA, developed in North America, EU and East Asia all of which that will be used to convert the output ALMA data into ground breaking science. Or the telescopes themselves which are a collaborative effort, with a fraction of the final 66 dishes being provided by each of the ALMA partners. And the elements of the support network of documentation and websites for both professional astronomers and the interested public, such as yourselves, which have been created by many, many people all over the world.
It’s from these sometimes seemingly small, or massive building blocks that huge and revolutionary scientific projects, such as ALMA, can be achieved and why large-scale international collaborations make 21st century science (and astronomy in particular) a fascinating and highly enjoyable endeavor.
Particularly for those Scientists around the world who are eagerly awaiting their first data out of ALMA!
Well, that’s it for today; this has been Adam Avison for the 365 Days of Astronomy Podcast. Until next time… Goodbye
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365 Days of Astronomy
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