Multibeam RFI was removing too many pulses and triplets

Message boards : Nebula : Multibeam RFI was removing too many pulses and triplets
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Profile David Anderson
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Message 1952776 - Posted: 29 Aug 2018, 21:55:14 UTC

The idea of multibeam RFI removal is to find groups of signals that are similar (e.g. in time and freq) and that appear in non-overlapping beams. Terrestrial RFI often appears in different beams; celestial signals do not.

As of a few weeks ago, this was removing way too many (like 90%) pulses and triplets. My last change - which tightened up the notion of "similarity" in time and frequency - reduced this to about 15%, but it was still removing too much. The issue is that pulses and triplets have an attribute, namely period, that other signal types don't. Pulses or triplets that are close in time and frequency, but not close in period, should not be viewed as similar.

So, working with Eric, I added a period check to the similarity test for pulses and triplets. For pulses, we now require that the periods agree within 1%; for triplets, they must agree within half the time resolution for that FFT length.

This seems to have worked. The multibeam removal fraction is down to about 3% for both signal types, and I think we're still removing actual RFI. I reran the pipeline with this change and results are online. Please look at waterfall plots; if you find any RFI anomalies, please bookmark them and let me know.
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Message 1952896 - Posted: 30 Aug 2018, 15:19:15 UTC

Thanks for your continued effort. Could you explain how often are newly completed SETI@home workunits fed into Nebula and how often is "Sky coverage" updated? Are data coming from Breakthrough Listen processed by Nebula?[/url]
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Message 1953020 - Posted: 31 Aug 2018, 9:11:32 UTC

Any update on the plan to use the Atlas cluster at Einstein?
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Message 1953031 - Posted: 31 Aug 2018, 12:17:11 UTC

any plans to rework all the working units already processed and have been deleted of all its potential alien signals ?
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Message 1953039 - Posted: 31 Aug 2018, 13:21:04 UTC

Michel,

As I understand it, and I believe I'm right, the original plan was to run stored work-units though the Nitpicker m/c for a second sift. But after a re-think they decided to do it in real time. That would have meant a m/c costing $30-40K but the money wasn't there. DA formulated a plan to get access to the Atlas cluster at Einstein in Hanover, but that has been delayed due to birdie testing. DA does a lot of work for BOINC apart from the Nebula project.

Stored away is work from the Arecibo and now GBT dishes, presumably soon Parkes.
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Message 1953075 - Posted: 31 Aug 2018, 19:20:53 UTC - in response to Message 1953039.  
Last modified: 31 Aug 2018, 19:21:15 UTC

Stored away is work from the Arecibo and now GBT dishes, presumably soon Parkes.



Do these new ones have been fixed or those changes are not ON yet on these ?
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Message boards : Nebula : Multibeam RFI was removing too many pulses and triplets


 
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