Radio astronomy is a science based upon the study of naturally occurring radio emissions from objects in space. Because of the huge distances involved, these signals are extremely weak, far weaker than any manmade radio transmissions. As a result, the progress of radio astronomy has always depended upon the availability of ever more sensitive radio receivers and larger and larger antennas, to collect as much cosmic radio energy as possible.
Over the last couple of decades the progress made in making ever more sensitive radio receivers has been nothing short of astounding. Equally astounding have been the astronomical discoveries that this progress made possible. We have learned a lot about the distribution of material in galaxies, the formation of stars and new planetary systems, and have been digging back further and further in time, toward the time the first galaxies were forming and the first stars starting to shine. This has taken us to the limits of what we can do with existing radio telescopes. To proceed further will require a radio telescope about 100 times more sensitive than anything we now have. Canada and several other nations are now collaborating to build it.
Until about ten years ago the sensitivity of any radio receiver we could develop was limited by our engineering knowledge. Now the limits are the boundaries set by Mother Nature. We might be able to double the sensitivity by refining our engineering, but that won’t yield the 100 times increase we need. Fortunately there is a solution. Instead of increasing the sensitivity of the receivers, we can make larger antennas to collect more cosmic radio energy.
However, a single antenna with the required signal collecting area would be extremely expensive, even if we knew how to make such a behemoth. However, there is an alternative; we can make the antenna out of lots of small dish antennas – thousands of them. We are very good at making small dishes, but if we want to make thousands of them the total cost has to be considered. We will have to minimize the engineering and material costs, and also the manufacturing costs. We need a design we can mass produce.
The approach being researched at our observatory is to use carbon-fibre based composites rather than steel or aluminium, which are the usual materials. There are two main reasons for this. Firstly these composites offer about 200 times the strength compared with the same weight of steel. Secondly, because the dishes are made by layering materials on a mould, making many is not a major problem. Two have been made so far. One is being used as a test bed for the development of other components for that new radio telescope.
These days we see dish antennas all over the place, and it is clear that a means to manufacture relatively inexpensive, high quality dishes in large quantities will have applications beyond radio astronomy. This is just one more example of the technical spin-offs from radio astronomy, which has produced advances in receiver and antenna design, and in imaging and signal processing techniques, among other things.
The summer solstice, the northernmost point in the Sun’s yearly travels, will be at 10:16 PDT on the 21st. Jupiter, Mars and Venus form a procession out of the sunrise glow. Saturn is high in the south. The Moon will reach last quarter on the 23rd.
Ken Tapping is an astronomer with the National Research Council’s Herzberg Institute of Astrophysics, and is based at the Dominion Radio Astrophysical Observatory, Penticton.