SETI@Home (classic)

From Just Solve the File Format Problem
Jump to: navigation, search
File Format
Name SETI@Home (classic)
Extension(s) .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


Sample data

Other links

Personal tools