Radio Astronomy and SETI Jenny Bailey G0VQH Bernie Wright G4HJW Introduction History of Radio Astronomy SETI Practical Radio Astronomy Practical SETI Questions Today’s lecture will be presented by myself - Jenny Bailey - G0VQH and Bernie Wright - G4HJW. Bernie will concentrate on Radio Astronomy, and I will talk about SETI. We hope to limit ourselves to about an hour.

Is there anyone out there ? The Drake Equation : Where N = The number of civilisations trying to contact us R = The average rate of Star Formation fp = The fraction of stars that are suitable for planet formation ne = Number of Earth-like planets fl = Fraction of Earth-like planets where life develops fi = Fraction of Earth-like planets where life has intelligence fc = Fraction of intelligent species who want to communicate L = Lifetime of a civilisation The Drake Equation : Not really an equation at all, more a indication of probability Number of stars in our galaxy 20 stars within 12 light years

Where Should we look Frequency Polarisation Direction Radio Leakage Radio - The ‘Water Hole’ Optical Gravity Waves The next big discovery Polarisation Circular, linear, modulated ? Direction Targeted search All-Sky survey Radio Leakage Intentional messages RF leakage Modulation Narrow band signals - preferably pure CW. Show a picture of the ‘Water Hole’ The next big thing - We have only had radio for 100years, useful radio for less than 50. There may be a communication medium that we do not know about. This could be where everyone is talking at the moment. Until then, we must use our best hope for CONTACT - Radio. Which Frequency - There is no Wrong frequency - However the microwave window - Hydrogen line - protected frequency - less interference. Other SETI Projects - Optical SETI - Planetary Society We do not know the speed of a Gravity wave. The first high-power VHF broadcast that might leak into space was the 1936 Olympic speech from Germany - it would be difficult to detect wide modulated signals. Leakage- Radar might be long range - pulsed transmissions - difficult to tell from white noise Leakage - Mr Mandlebrot said that there is more to white noise other than the spectrum. There may be other algorithms for extracting patterns from noise.

The ‘Water Hole’ The Hydrogen line Frequency is 1420.406MHz with Doppler shift taking the frequency lower. The Hydroxyl lines are 1612.231, 1665.402, 1667.359 and 1720.530. These have protective bands around them. Called the water hole because H + OH = water. Other water-based lifeforms might find this band significant. Hydrogen is the most abundant molecule in the Universe.

SETI Projects Arecibo/Jodrell Bank Project Argus SETI@Home Optical SETI Project Argus is a collection of volunteers co-ordinated by the SETI League. Project Argus is an effort to deploy and coordinate roughly 5,000 small radiotelescopes around the world, in an all-sky survey for microwave signals of possible intelligent extra-terrestrial origin. When fully operational, Project Argus will provide the first ever continuous monitoring of the entire sky, in all directions in real time.The aim is to have a 3-5m dish pointed at every point in the sky listening on 1420MHz SETI@Home The project has three major components: Data collection. SETI@home is working closely with SERENDIP, a SETI project based at UC Berkeley, which has continuous access to the Arecibo radio telescope Data analysis. We have developed a program that searches for strong signals at 4,000,000 different combinations of frequency, bandwidth, and chirp. Distributed computation. We have developed server-based software that divides the radio telescope data into chunks, distributes these chunks to clients, and collects the results.

How far can we hear ? Distant civilisation wants to signal us. Tx : Assume 1GW into a 300m dish at 1420MHz . Rx : Assume Project Argus station as receiver - 4m dish. GaAsFET LNA 10Hz channels. 20 nearest stars are less than 12 light years away. The distant civilisation may choose to send signals out to likely looking Planetary System. Arecibo is 300m. Mankind could Generate 1GW if we needed to. 10 second pulses to lower the bandwidth required for receive. Assume a Uniform Distribution of Stars of 0.01/Light Year.

What signal should we look for ? A signal with Doppler shift A signal with Doppler shift would indicate non-terrestrial. CW signal to get attention A CW beacon would stand out from Galactic noise Can be seen with low bandwidth receiver A modulated signal This will spread the signal over a wide bandwidth and make the signal hard to detect Doppler shift - However, could the satellite or plane. A polite alien would correct their Doppler shift to Galactic centre. There are no known coherent natural noise sources around this frequency. Long pulse time to enable processing of signal below the noise. Depending on the signal and modulation type, there will be little or no carrier. Old AM transmissions were inefficient. New digital transmissions IE TETRA have little carrier and would not be easily detectable.

Should we Transmit A signal was sent from the Arecibo Telescope to celebrate its commissioning. This was controversial because : The message was very USA-centric. It was argued that any message should be agreed by all nations. We should not attract attention to our planet, we might invite BAD aliens. The message was sent See Hollywood’s output for the last 40years - Independence Day

How do we search ? We need to look at as much Bandwidth as possible The receiver must have a narrow Bandwidth to enhance the sensitivity Use an ex-PMR FM radio modified to product detect - creating a 25KHz wide SSB receiver Synthesise narrow receive filters using PC running FFT software to chop the receiver bandwidth into many 10Hz channels. Average each 10Hz channel over a few seconds to improve receiver sensitivity

Signal Verification A signal from a distant star will have the following characteristics : The signal will come and go with the response of the receiving aerial The signal will have Doppler shift corresponding to the Earth’s spin and rotation around the sun.