The complete message is about 400,000 bits long and will be transmitted three times over a 3-hour period in the direction of the four selected stars. Then, it will be followed by a series of greetings from people around the world. The transmission will start on March 15 1999. This message is much larger in size, duration and scope than the one sent by Frank Drake on November 16th, 1974 from the Arecibo observatory which consisted of only 1,679 bits sent over a 3 minute duration.
Finding a transmitter for this task was not easy; the project will use a 70 m (230 ft) Ukrainian antenna equipped with a 150 kW transmitter broadcasting at 5 GHz (6 cm). Using this antenna, any civilization within 100 light-years which has access to a radio-telescope with an area of one squared-kilometer will be able to read the message. The artificial nature of the message should be able to be detected by similar instruments at distances up to 10,000 light-years. A radio-telescope of this size will be built on Earth in the near future.
The message itself has been designed using some of the principles of interstellar communication proposed in the early works of Hans Freudenthal, Frank Drake and Carl Sagan. Mathematics and physics have been used to define the message, so that it will be clear and based on universal concepts. For example, the hydrogen atom can be used to describe quantities such as mass, electric charge and length. To these basic ideas were added simple notions of astronomy, biology, geography and cosmology. Easier concepts and ideas are at the beginning while the more elaborate ones appear at the end of the message. Any true communication is not complete without an answer. Therefore, the last page of the message invites anyone who reads it to reply, sending information about themselves.
The message has been built to minimize the loss of information due to noise introduced into the signal during its interstellar flight. To minimize the risk of confusion, a set of characters was created which are fairly different from each other. Redundant information is included to allow cross-checking of the message. The addition of a frame around each page of the message, and the inclusion of page and section numbers will also help the translation process.
For many years, most research projects dedicated to the Search for Extra-Terrestrial Intelligence (SETI) have scanned the sky trying to detect any signals sent by extra-terrestrial civilizations willing to communicate with us. So far, the sky has remained silent. All these searches have been passive: what is proposed now is to send a message in order to catch the attention of an extra-terrestrial civilization.
In order to maximize the probability of detection, the direction of the transmission has been carefully chosen to include stars similar to our Sun, and to limit the degradation of the signal as it travels through the vast reaches of interstellar space. Fortunately, there is a region between the spiral arms of our galaxy where the signal can be transmitted over long distances without too much degradation. This region is situated between 50 and 90 degrees of galactic longitude, which corresponds roughly to the region of the sky called the "Summer Triangle". Four stars, clones of our Sun, have been selected from the list made by the SETI institute. These target stars are located at distances between 50 and 70 light-years from the Sun.
Names l |b| a (J2000) d (J2000) Type D(lyr) V HD190360 67 1 20h03m37.41s +29d53m48.51s G7V 51.8 5.73 HD190406 57 8 20h04m06.23s +17d04m12.64s G1V 57.6 5.08 HD186408 83 13 19h41m48.95s +50d31m30.21s G3V 70.5 5.99 HD178428 50 4 19h07m57.32s +16d51m12.24s G6V 68.3 6.08
Table headings: l and |b| are the coordinates of the target star in galactic latitude and (absolute) longitude, while a and d give the Right Ascension and Declination of the star in the J2000 coordinate system. The star's spectral type is given next; for comparison, our Sun is a G2V. The next column gives the distances to each star in light years. The last column gives the Visual magnitude (brightness) of each star;
You can also visit the web site of the Encounter 2001 project