Radio Meteor Detectors

One of the pioneers in detecting meteors using radio waves was Sir Bernard Lovell. His work during the war, helping develop radar, stood him in good stead when it came to meteor detection later. His main area of research was in the detection of Cosmic rays and at that time he knew very little about astronomy in general.

His work for Manchester University took him to a quiet location near Chester, Jodrell Bank. A little-known place owned by Manchester University Botanical Department, it was a quiet location away from electrical interference, and was ideal for Sir Bernard to investigate cosmic rays.

Next to the wooden hut was his ex-army radar unit, and on the 14th December 1945 the first day’s work, he switched on in the afternoon. To his surprise he was picking up lots of reflections which he deduced were not cosmic rays, but later he concluded they were meteors. This was quite a fortunate event as the 14th December is the peak of the Geminids meteor shower. This lead him on to studying meteors for the first 2 years at Jodrell Bank.

Today here at Sherwood Observatory we study incoming meteors by using two different methods. “Forward scatter” and “Backscatter” techniques.
The top larger Yagi antenna is pointed towards BRAMS (Belgium Radio Meteor Stations) radar station in Belgium and detects meteors in the forward scatter configuration.

The smaller lower Yagi is aimed at the GRAVES (Grand Reseau Adapte a la Veille Spatiale) radar station in the south of France and detects meteors in the backscatter configuration. The GRAVES radar is used by the French government to detect the trajectory of satellites that pass over their territory.

Hydrogen Line Radio Telescope

This radio telescope with a 1 metre steerable arm uses a frequency of 1420MHz (21cm wavelength) to detect the emissions of Monatomic Hydrogen that are found in between the arms of our galaxy.

Looking out away from the centre of our galaxy, i.e. away from the constellation Sagittarius, towards the star Deneb in the constellation of Cygnus (the Swan), we find 3 arms of our galaxy that we can view with this telescope.

The first is our local arm – know as the Orion arm. Behind that is the Perseus arm, with the Cygnus arm, or outer arm furthest afield.

Solar and Jupiter/Io antenna (20 MHz)

This antenna sits just below the 15m Ham band (20MHz). High energy emissions from the Sun can be detected at this frequency.

Normally this type of antenna is formed by a twin split dipole of 15m in length. However due to the space available to us this is impractical, so a 1/4 wavelength “Reflecting Loop” antenna was designed.

This antenna also enables us to detect the interactions between the Jupiter/Io system. lo is the innermost and third largest of the four Galilean moons of the planet Jupiter.

At an average distance of 262,000 miles from Jupiter, Io cuts across the planet’s powerful magnetic lines of force, thus turning Io into an electric generator. Io can develop 400,000 volts across itself and create an electric current of 3 million amperes. This current takes the path of least resistance along Jupiter’s magnetic field lines to the planet’s surface, creating lightning in Jupiter’s upper atmosphere.

As you might imagine, this lightning creates radio frequency emissions and directs them away from the system like a lighthouse. When the beam points towards the Earth our antenna can detect the signals.

SuperSID (Sudden Ionospheric Disturbance)

The SuperSID (Sudden Ionospheric Disturbance) antenna uses an indirect method of detecting radio emissions generated from solar flares by the sun.

The Sun ionises our atmosphere in the Ionosphere during the daytime and produces a new reflective layer called the “D” layer some 40 to 55 miles up. This D layer is highly reflective to VLF (Very Low Frequency) radio waves, similar to the energy output of the sun.

If we monitor transmitters at these frequencies, when a flare happens, the reflectivity of the “D” layer changes, and therefore the strength of the signal we receive changes. Hence, we detect the flare.

The two main transmitters we monitor are at Skelton and Anthorn in Cumbria. These transmitters are used to talk to naval submarines as these frequencies pass through water up to 200m deep.

At various times we also monitor transmitters in Germany, Italy, and Iceland.

Solar Telescope

We are currently developing a 1.2 metre solar telescope to receive signals from the Sun at the 10.7cm waveband (2.8GHz).

The 10.7 cm solar radio flux, which originates high in the Chromosphere of the Sun and low in the Corona of the solar atmosphere, is an excellent indicator of solar activity. The F10.7 radio emissions measurements are completely objective, because they can be made in all types of weather.

NOAA Weather Satellite antenna

Sherwood Observatory downloads data from the NOAA-15, NOAA-18, NOAA-19 and NOAA-20 satellites, launched by The National Oceanic and Atmospheric Administration as part of a series from 1970 to 2017.

These satellites orbit the Earth in a polar orbit, passing over us about 4 times a day. The signal transmitted by the NOAA satellite is an encoded signal which is transmitted to Earth via radio waves. The signal can be recorded using an antenna and software-defined radio. This recording can then be converted into an image.

While still operational, several instruments aboard the NOAA-18 satellite have failed, however, it still gives us great images of cloud cover over the UK, Europe, and the Scandinavian countries.