Radio astronomy
Radio astronomy is the most accessible form of ground-based astronomy, as the atmosphere is almost completely transparent at most radio wavelengths. This means that almost all of the radio waves aimed at the Earth make it to the ground. Unlike optical astronomy, the Sun being up generally doesn’t affect the observations. This means that radio observatories can operate 24 hours a day.Unfortunately, it’s not all good news for the radio astronomers though. There are two main problems that they have to overcome: low energy photons, and radio interference.
Radio waves are the longest wavelength of all electromagnetic radiation, and so it has the least energy of them. If you were to sum up all the energy from all the radio waves observed since the start of radio astronomy, it would not add up to enough energy to melt a snow flake. So, radio astronomers are dealing with very small amounts of power! The first way which radio astronomers overcome this is to increase the size of the dish which they use to collect the signal. For example; the Parkes Radio Telescope (Australia’s largest radio telescope) is 64m in diameter, while the largest optical telescope in the world is only 10m in diameter!
By making larger and larger telescopes you can see fainter objects and get better angular resolution (more detail). So, another trick astronomers use to increase the quality of the data they get is to use an array of telescopes. This is called an interferometer. Interferometers work by combining the signal you get from multiple telescopes, to give you the angular resolution of one telescope the size of the distance between the two (e.g. If you were to record the signal from two identical telescopes 1km apart, you would see with the same detail as a 1km telescope). An added bonus of interferometry is that during the correlation process you can remove any information not in both signals (ie local interference).
The other problem that radio astronomers face is radio frequency interference (RFI). Humans love transmitting things in the radio band, as it’s easy to create and easy to receive, so the radio band is heavily polluted with man-made signals. To combat this, Radio Quiet Zones have been established around radio observatories and potential radio observatory sites, to keep the RFI to a minimum. Unfortunately, this doesn’t always completely remove the RFI as almost everything electronic gives off some form of RFI (from your favorite radio station, to your mobile phone, and even you computer!).
When you combine the two solutions to the problems, you end up with the future of radio astronomy: large-scale interferometers, placed in large, semi-isolated (and radio quiet) areas. The Square Kilometre Array (SKA) is an example of this.
Radio waves are the longest wavelength of all electromagnetic radiation, and so it has the least energy of them. If you were to sum up all the energy from all the radio waves observed since the start of radio astronomy, it would not add up to enough energy to melt a snow flake. So, radio astronomers are dealing with very small amounts of power! The first way which radio astronomers overcome this is to increase the size of the dish which they use to collect the signal. For example; the Parkes Radio Telescope (Australia’s largest radio telescope) is 64m in diameter, while the largest optical telescope in the world is only 10m in diameter!
By making larger and larger telescopes you can see fainter objects and get better angular resolution (more detail). So, another trick astronomers use to increase the quality of the data they get is to use an array of telescopes. This is called an interferometer. Interferometers work by combining the signal you get from multiple telescopes, to give you the angular resolution of one telescope the size of the distance between the two (e.g. If you were to record the signal from two identical telescopes 1km apart, you would see with the same detail as a 1km telescope). An added bonus of interferometry is that during the correlation process you can remove any information not in both signals (ie local interference).
The other problem that radio astronomers face is radio frequency interference (RFI). Humans love transmitting things in the radio band, as it’s easy to create and easy to receive, so the radio band is heavily polluted with man-made signals. To combat this, Radio Quiet Zones have been established around radio observatories and potential radio observatory sites, to keep the RFI to a minimum. Unfortunately, this doesn’t always completely remove the RFI as almost everything electronic gives off some form of RFI (from your favorite radio station, to your mobile phone, and even you computer!).
When you combine the two solutions to the problems, you end up with the future of radio astronomy: large-scale interferometers, placed in large, semi-isolated (and radio quiet) areas. The Square Kilometre Array (SKA) is an example of this.