The Future of Radio Astronomy : Options for Dealing with Human Generated Interference

Radio astronomy provides a unique window on the universe, allowing us to study: non-thermal processes (galactic nuclei, quasars, pul-sars) at the highest angular resolution using VLBI, with low opacity. It is the most interesting wave band for SETI searches. To date it has yielded 3 Nobel prizes (microwave background, pulsars, gravitational radiation). There are both exciting possibilities and substantial challenges for radio astronomy to remain at the cutting edge over the next 3 decades. New instruments like ALMA and the SKA will open up new science if the challenge of dealing human generated interference can be met. We summarise some of the issues and technological developments that will be essential to the future success of radio astronomy. 1. Telescope Sensitivity Moore's law for the growth of computing power with time (ie a doubling every 18 months) is often quoted as being vitally important for the success of the next generation of radio telescopes (working at cm wavelengths) such as the Square Kilometre Array (SKA). It is worth noting that radio astronomy has enjoyed a Moore's law of it own, having a exponentially improvement in sensitivity with time as shown in Figure 1. In fact the doubling time is approximately 3 years, and has been in progress since 1940, giving an overall improvement in sensitivity of 10 5. However, we are approaching the fundamental limits of large mechanical dishes and noise limits of broad band receivers systems. We need to look to other means of extending this growth into the future. Why do we want to be on this exponential growth curve ? Fields of research continue to produce scientific advances while they maintain and exponential growth in some fundamentally limiting parameter. For radio astronomy sensitivity is definitely fundamentally limiting. An interesting question is whether there are other parameters for which as exponential growth could be maintained for a period of time. The first and most obvious point about exponential growth is that it cannot be sustained indefinitely. Can we maintain it for sometime into the future ? There are 2 basic ways to stay on the exponential curve: 1) Spend more money, 2) Take advantage of technological advances in other areas.