Editing SETI@home (section)

==Procedure details==
SETI@home searches for possible evidence of radio transmissions from [[extraterrestrial intelligence]] using observational data from the [[Arecibo Observatory|Arecibo radio telescope]] and the [[Green Bank Telescope]].<ref>{{Cite web|url=https://seti.berkeley.edu/listen/research.html|title=Berkeley SETI|website=seti.berkeley.edu|access-date=10 June 2017|archive-date=July 31, 2018|archive-url=https://web.archive.org/web/20180731153757/https://seti.berkeley.edu/listen/research.html|url-status=live}}</ref> The data is taken "piggyback" or "passively" while the telescope is used for other scientific programs. The data is digitized, stored, and sent to the SETI@home facility. The data is then parsed into small chunks in frequency and time, and analyzed, using software, to search for any signals—that is, variations which cannot be ascribed to noise, and hence contain information. Using volunteer computing, SETI@home sends the millions of chunks of data to be analyzed off-site by home computers, and then have those computers report the results. Thus what appears a difficult problem in data analysis is reduced to a reasonable one by aid from a large, Internet-based community of borrowed computer resources.

The software searches for five types of signals that distinguish them from [[Electromagnetic interference|noise]]:<ref>{{cite web |url=http://seticlassic.ssl.berkeley.edu/about_seti/about_seti_at_home_4.html |title=How SETI@Home Works – What is SETI@home Looking For? |publisher=SETI@Home Classic |access-date=23 June 2010 |archive-date=September 9, 2019 |archive-url=https://web.archive.org/web/20190909020950/http://seticlassic.ssl.berkeley.edu/about_seti/about_seti_at_home_4.html |url-status=live }}</ref>
* Spikes in [[power spectrum|power spectra]]
* [[Gaussian function|Gaussian]] rises and falls in transmission power, possibly representing the telescope beam's [[main lobe]] passing over a radio source
* Triplets&nbsp;– three power spikes in a row
* [[Pulse (signal processing)|Pulsing]] signals that possibly represent a [[narrowband]] digital-style transmission
* [[Autocorrelation]] detects signal waveforms.

There are many variations on how an ETI signal may be affected by the interstellar medium, and by the relative motion of its origin compared to Earth. The potential "signal" is thus processed in many ways (although not testing all detection methods nor scenarios) to ensure the highest likelihood of distinguishing it from the scintillating noise already present in all directions of outer space. For instance, another planet is very likely to be moving at a speed and acceleration with respect to Earth, and that will shift the frequency, over time, of the potential "signal." Checking for this through processing is done, to an extent, in the SETI@home software.

The process is somewhat like tuning a radio to various [[Channel (broadcasting)|channels]], and looking at the signal strength meter. If the strength of the signal goes up, that gets attention. More technically, it involves a lot of digital signal processing, mostly [[discrete Fourier transform]]s at various [[chirp]] rates and durations.