View source for SETI@Home (classic)

{{FormatInfo
|formattype=electronic
|subcat=Distributed computing projects
|extensions={{ext|sah}}
|released=1999
}}

'''SETI@Home''' is a distributed computing project to analyze data from radio telescopes for signals that could possibly be evidence of intelligent life in outer space. The SETI (Search for Extra-Terrestrial Intelligence) project has managed to get some time on such massive telescope arrays as the one in Arecibo, Puerto Rico, but the task of analyzing the data takes a large amount of computing resources which once would have required an expensive supercomputer; now it is done by sending the data in chunks called "work units" to participating users' computers (PC, Mac, Unix, etc.), where they are processed (usually in the background when the computer is otherwise idle).

SETI@Home originally operated with its own custom program (termed the "classic" version), but later joined the [[BOINC]] system as one of a number of projects users of that software can choose to have their computers work on.

== Classic data files ==

The data files for SETI@Home Classic are found in the same directory that the program itself is installed in, which for the Windows version is usually '''\Program Files\SETI@Home'''.

Most of the data files have the '''.sah''' extension. They are generally in UNIX-style [[ASCII]] text format, with lines broken with linefeed characters. Much of the data is in the form of name/value pairs each on a separate line with the equal sign separating the name from the value.

Work units are in files called '''work_unit.sah''', starting with a line ''type=work unit''. Encoded binary data follows the header fields (which end with ''end_seti_header''). The binary data is in the [[PSRFITS]] format, a variety of the [[Flexible Image Transport System]] (FITS). It is encoded as ASCII characters (there doesn't seem to be any online documentation specifying the specific encoding scheme used; it is perhaps something like [[Base64]], [[Uuencoding]], or [[BinHex]]).

Results are stored in a file '''outfile.sah''', with data like:

 <ogh ncfft=11 cr=0.000000e+000 fl=64>
 triplet: power=8.271954e+000 mean=3.871512e-003 period=2.067662e+000 ra=27.738 dec= 17.33 time= 2453131.24892 freq=1419438781.74 fft_len=64 chirp_rate=0.000000e+000
 triplet: power=8.185313e+000 mean=3.912492e-003 period=2.067662e+000 ra=27.738 dec= 17.33 time= 2453131.24892 freq=1419438781.74 fft_len=64 chirp_rate=0.000000e+000

There are several other .sah files with configuration, status, and account information.

== Data format documentation ==
* [http://seti.berkeley.edu/book/export/html/236 Raw data format description]
* [http://www.atnf.csiro.au/research/pulsar/psrfits/ PSRFITS pulsar data format]

== Software ==
* [http://code.google.com/p/seti-psrfits-viewer/ Viewer for SETI PSRFITS files]
* [http://swap.poupe.net/sk/ SETI@home Keeper]
* [http://www.mariovaldez.net/software/phpsetimon/ PHP SETI@home web monitor]
* [http://gamma.nic.fi/~jknutar1/wu2wav/ WU2WAV] - converts work units to [[WAV]] sound files

== Sample data ==
* [https://www.dan.info/sampledata/work_unit.sah Work unit]
* [https://www.dan.info/sampledata/outfile.sah Result file]

== Other links ==
* [http://setiathome.berkeley.edu/ SETI@Home site]
* [http://seticlassic.ssl.berkeley.edu/ SETI@Home Classic site]
* [http://setiathome.berkeley.edu/transition.php Transition to BOINC]
* [http://setiathome.berkeley.edu/forum_thread.php?id=65274 Discussion of analyzing data]
* [http://www.pisa.org.hk/event/bo.pdf Presentation describing a buffer-overflow exploit in SETI@Home data]