Radio Astronomy started with a search for the causes of interference to Trans-Atlantic radio communications. When it was discovered that radio waves did indeed come from beyond the Earth a new Science was born. ( Karl Jansky )
We associate the Dish Antenna with radio astronomy as most research has been done at very high frequencies. To do research at lower frequencies larger antenna are needed due to the longer wavelengths. For this reason phased arrays are popular and many innovative designs have been implemented.
|The European LOFAR LOw Frequency ARray was the first of a new design to use many small antenna working together in 'Tiles' to increase sensitivity. The development started in the Netherlands and has also been implemented in many other European countries.|
The Netherlands Institute for Radio Astronomy website contains a wealth of information and a fascinating history of interferometers around the World.
|In the USA the Long Wavelength Array is a compact array radio telescope operating in the 10-88 MHz band, colocated with the Very Large Array in central New Mexico. LWA1 currently consists of 257 dual-polarization active dipole antennas in a 100 m x 110 m elliptical footprint with an outlier dipole antenna located approximately 300-m east of the main array. Each dipole is individually digitized and then formed into 4 beams using a delay-and-sum technique. The beams can be pointed independently; thus LWA1 can be used similarly to 4 separate radio telescopes. The individual dipole signals can also be recorded. A subset of LWA1 science targets includes pulsars, astrophysical transients, the Sun, Jupiter, and the ionosphere, but innovative, technically feasible investigations of all kinds are welcomed.|
|As part of the Square Kilometer Array, the Murchison Widefield Array in Western Australia deploys Low Frequency Arrays designed to operate on VHF frequencies around 150MHz. Crossed Dipole antenna are grouped in a 4 x 4 grid and the resulting 32 individual signals are delayed in a beam-former to point the array in a certain direction.|
Low Frequency Radio Astronomy is a fascinating area of study. Many sources of decametric emissions (10 - 100MHz) can be found in the sky. Wherever magnetic fields and electric current coincide, some sort of radio emission will occur.
The ASV Low Frequency Array will give us a new window of study into the Universe. I started using the project name 'Project Skylight' back in 2013 when the idea of building this instrument was first thought of.
Some experimenting was carried out with different antenna designs. Some were not stable enough. Some were impracticable to build in great numbers or just too expensive.
We have now reached a point where we have started building the electronics and writing the software to control the array.
The array will consist of many receivers spread around a few hundred metres and connected back to a central control computer through optical fibre and low voltage power cable. Each receiver will have eight antennas connected to it and be able to electronically point to a different section of the sky.
Receivers will detect radio energy and convert it to data to be sent back to the control computer. All the information from the receivers will be put together to make an image of the sky at radio frequencies.
The control computer will allow for observations of the sky by scheduling the time, radio frequency and location to observe. The data is recorded and analysed. We hope to be able to make real time images of the sky and display them on the website.