[ Introduction | [email protected] | Seti view | tkseti | X-Seti | Seti herder | Hints ]
Large radio telescopes worldwide receive electromagnetic waves coming from the depths of space. Attempting to locate alien intelligent communication or trying to contact other life forms, these telescopes should find proof.This search is not easy because many natural phenomenon also send electromagnetic waves into space. These waves are also interesting for scientists because they allow us to deduce the construction of regions in space (like the 21-cm-line including information about hydrogen concentration). These lines interfere with the search for waves coming from artificial sources. This naturally occurring "noise" has to be subtracted and the remaining peaks might be the searched signals. This work takes a lot of PC-power and new data arrives hourly.
necessary program to derive the data is called setiathome.
The different version for the different platforms are
available at http://setiathome.ssl.berkeley.edu/. After you untar the program, you
should copy it to /usr/local/ and create a
symbolic link (ln -s) to the binary file setiathome
in /usr/local/bin/. This way every user will have
access to it if /usr/local/bin/ has been added to
the default path with $PATH.
Before starting you should create the subdirectory ~/setiathome/ where the received data and some more files are saved. Then change to this directory and start setiathome there. (You should always to change into the seti directory before starting because the data are always saved in the directory where you start setiathome.)
During the first start, you need a connection to the internet because you have to announce yourself to the seti server. The program asks for 1) your email address which is used as the ID, 2) a nickname, 3) your home country and 4) if you work at a school, home or company computer. Then it connects to the [email protected] server and announces you. After that, your first data package will be downloaded and the calculations will begin.
[email protected] was designed to work as a screen saver and should only work when you do not use your computer. Because a universal screensaver does not exist at Linux, including it into other programs is not easy. Still, Linux, like all Unix systems, offers the ability to establish a priority to the program using the command nice. [email protected] has included it as an option which can be invoked at startup with:
>> setiathome -nice 20
The program will be
started with the lowest priority and it only slows down
the system just a little bit. If you want to start it in
the background or you are not interested in the output
you should start it with the option -email. To
suppress the output you should add >/dev/null at
After working through the whole data setiathome tries to connect the seti server to send the results and get the new data. If it does not find the server it will retry it in 60 minutes. It is much more efficient to stop the program and, after dialing into the internet, restart it again.
With the option -stop_after_process, setiathome will not try to connect the server after finishing the file.
If your PC is very fast and you manage to process more than one data file between the two dial-ins, you could create more seti directories. Every job needs its own directory where you have to call setiathome, otherwise errors could occur if two programs work on the same data.
Setiathome runs in a console and does not create any graphical output. The prompt shows how what percentage of the data has been processed and where the data came from. You can find some programs on the internet that offer graphical frontends for setiathome. Setiview is one of these frontends, not for X-Windows, but for the console. In addition to displayinginformation about the source of the data (telescope, frequency, direction, etc.), it offers a view of the percentage of data that has been processed.
Many companies have a connection to the internet and the PCs are not switched off in the night. Every night thousands of computers are "sleeping" and their capacities are not used. These illustrations show how much sense it could make if these companies "offer" their PCs for public research and run setiathome on their network. Even if you own a MS Windows computer you, are able to use the client. But Linux users have it much easier because the client can be started via a script every night and then stopped automatically in the morning before you reach your working place. This could be managed using crontab, a program that runs programs at a specific time. Either you change it with a text editor by starting it with
>> crontab -e
or change it easily with
vcron (LinuxNetMag: vcron and kcrontab).
Additionally, you need a script that handles starting and stopping via a script. This script is a changed init-script which starts and stops programs during booting and rebooting. You will find the script here to download it. (To start the program it has to be changed to an executable with chmod +x filename)
Of course you have to adjust the script to your paths. Change the variable SETIDIR. It is the guide to your seti directory where the data are saved. With nice you set the nice value for setiathome which has to be an integer between 0 and 20. The higher the value, the less the priority of the program.
For example, it you work from 9:00 a.m. to 5:00 p.m., you could write in the crontab (after starting crontab -e):
|# start setiathome daily at 5.00 pm
00 17 * * * /path/to/seti-script-user start
# stop setiathome daily at 9.00 am
00 9 * * * /path/to/seti-script-user stop
| # start setiathome
friday(5) at 11.00 pm
00 23 * * 5 /path/to/seti-script-user start
# stop setiathome monday(1) at 1.00 am
00 1 * * 1 /path/to/seti-script-user stop
will start setiathome every Friday night
and stop it every Monday morning.
Much more information about crontab is available typing
or, if installed ,
>> tkman crontab
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