Nature of project: experimental, data analysis
Available to students on full-time physics degree schemes or joint students.
Pulsar radio emissions of 30Hz were detected from the Crab Nebula pulsar by Jocelyn Bell Burnell in 1967 and optical flashes by Michael Disney in 1969. By videoing the region in the vicinity of the Crab Nebula with a 25Hz TV camera, beat frequncies will slow down the apparent flash to around 6Hz, making it more easily detactable. PAL 25Hz video that will be taken and supplied by your supervisor, using his new 16 inch telescope, can be used to detect these flashes using Fourier analysis techniques to try to pick up the weak signal from this 16th magnitude star against the background noise.
Detection of short period repeating signals at "optical" wavelengths has not been explored much in astronomy as, apart from Pulsars, there should not be any natural astrophysical processes out there capable of making repeating signals of a few tens of Hz to 0.01 Hz freq range. Therefore a 2nd goal of the project is to take video of sections of the night sky, through a telescope, and apply either Fourier, or wavelet, analysis to search for repeating signals. Having proven, with the Crab Nebula puslar data, that the technique works, it can be tested out as a method for the Search for Extraterrestrial Intelligence (SETI). This has been attempted before using Radio Telescopes, and there are some efforts to undertake optical searches too for evidence of Laser Communication - although that has concentrated on the detection on nano-second laser pulses.
You will utilize either a remotely operated telescope, or borrow a smaller portable telescope to setup on campus/from home. This will be used to take low light sensitive camera video of the some parts of the sky for several minutes e.g. concentrating on a globular star cluster, or stars known to have terrestrial type planets in the habitable zone. Only one telescope need be used because there will be plenty of stars in the image field of view, but if only one of them exhibits evidence of a periodic signal and the others don't, then this would constitute a detection - so long as it was a say 3.5 sigma above the expected background noise for detection of a repeated signal.
A successful project will develop beyond the above in one/some of the following directions:
1) Perform theortical calculations of data capacity (Baud rate) and the power requirements needed to send data over a distance of several light years. You should take into account the signal to noise ratio at the receiving end of a telescope and whether this would be detactable against the bright glare from the parent star, or against the background night sky noise (away from a star), if coming from deep space.
2) How could detection capability and Baud rate be improved by mutiplexing at different optical wavelengths, and/or by using non-sinusoidal, but repeating complex signals?
When considering where to take your project, please bear in mind the time available. It is preferable to do fewer things well than to try many and not get conclusive results on any of them. However, sometimes it is useful to have a couple of strands of investigation in parallel to work on in case delays occur.
Additional scope or challenge if taken as a Year-4 project: Explore the use of low resolution diffraction gratings over the end of the camera to produce spectra, and look for repeating signals at different wavelenths e.g. multiplexing. You can use the spectra of adjacent stars to determine the noise levels.
Explore the use of linearly and circularly poalrized filters to try to detect repeating signals using this form of modulation.
Utilize archive video obtained from two of more simultaneous telescopic video recordings to help eliminate localized atmospheric cell effects that might induce false repeating signals in certain areas of the sky.
Produce Power Vs Frequency plots to help characterize background noise.
Please speak to Tony Cook (atc) if you consider doing this project.
Initial literature for students:
This can be done with just one telescope or utilize archive data. Some simple knowledge of photon noise and Fourier/wavelet analysis would help enormously. If using portable telescopes a brief instruction on their use will be needed. If using a remotely operated telescope, then a detailed instruction manual (and possibly a video) will be provided. A driving test on the telescope could be performed using TEAMS.
|milestone||to be completed by|
|Evaluation of optical detecion of Pulsar flashes||end of October|
|Evaluation of different optical SETI techniques and select some target areas of the sky||Christmas|
|Observation and/or analysis of archive video||end of February|
|Finish data analysis and evaluate signal to noise ratio characteristics||Easter|
Students taking this project will have to submit a full risk assessment form