Classification of Interstellar Radio Messages
During the preparation and transmission of any interstellar radio messages (IRMs), some scientific and technological issues need to be addressed. The paper «Messaging to Extra-Terrestrial Intelligence» (METI)  lists nine of such issues. We propose to rank planned and already sent IRMs depending on how well three basic METI’s issues are resolved in them. These basic issues are the following: (1) choice of the target stars, (2) energy required per bit of the information, and (3) availability of a special digital or analog key to allow Aliens to decode our message, . In order to rank IRMs, it is necessary to find out whether there are serious concerns regarding of how these three issues were addressed.
The corresponding analysis shows that to all three criteria mentioned above in the fullest measure satisfy five sent messages:
Arecibo Message 1974: http://en.wikipedia.org/wiki/Arecibo_message
Cosmic Call 1999: http://en.wikipedia.org/wiki/Cosmic_Call
Teen Age Message 2001: http://en.wikipedia.org/wiki/Teen_Age_Message
Cosmic Call 2003: http://www.cplire.ru/html/ra&sr/irm/CosmicCall-2003/index.html
A Message From Earth 2008: http://en.wikipedia.org/wiki/A_Message_From_Earth
All other IRMs cannot be considered as serious METI-projects. Without going into details and excluding all futile and advertising cases of broadcasts into Space (for example, advertising of beer, chips or the new popular scientific book), we end up with only a couple of examples. In the “Deep Space Communications Network” service, http://deepspacecom.net, radio messages are transmitting with no definite address, low power, and without any special encoding that would allow decoding of these messages at the receiving side. The message “Across the Universe”  was sent to the Pole star, a supergiant whose surroundings are not suitable for any life; besides the message was compressed by “terrestrial” algorithms and transmitted with inappropriately high speed. The list of other futile radio messages can be found in , and a short history of the interstellar radio messages is presented in .
Summarizing, we would like to notice that there is a clear and undoubted distinction between serious METI-projects and idle METI profanations. This allows avoiding discredits of the METI idea, which recently have developed into a new social phenomenon.
1. Alexander Zaitsev. Messaging to Extra-Terrestrial Intelligence, http://arxiv.org/abs/physics/0610031
2. John Walker. Self-Decoding Messages, http://www.fourmilab.ch/goldberg/setimsg.html
3. “NASA Beams Beatles’ ‘Across the Universe’ Into Space”, http://www.nasa.gov/topics/universe/features/across_universe.html
4. “List of Interstellar Radio Messages”, http://en.wikipedia.org/wiki/List_of_interstellar_radio_messages
5. Michael Marshall. Earth Calling: A Short History of Radio Messages to ET, http://www.newscientist.com/article/dn18417-earth-calling-a-short-history-of-radio-messages-to-et.html
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