QUESTION 17/2

RADIOCOMMUNICATION REQUIREMENTS FOR SYSTEMS
TO SEARCH FOR EXTRATERRESTRIAL LIFE

The C.C.I.R.,

(1976)

(a)

CONSIDERING

that many scientists believe intelligent life to be common in our galaxy;

(b) that electromagnetic waves are presently the only practical means of detecting the existence of intelligent extraterrestrial life;

(c)

(d)

(e)

S

that it is believed to be technically possible to receive radio signals from extraterrestrial civilizations; that, although it is not possible to know the characteristics nor to predict the time or duration of these signals in advance, it is reasonable to believe that artificial signals will be recognizable;

that, while an artificial radio signal of extraterrestrial origin may be transmitted at any frequency, it is technologically impractical to search the entire radio spectrum but the band searched should be sufficiently wide to make detection of a signal reasonably probable;

that technological and natural factors which are dependent on frequency determine our ability to receive weak radio signals;

(g) that while the search for radio signals from extraterrestrial civilizations has already begun, more sensitive systems will be in use by the 1980's which could receive harmful interference from very weak man-made signals;

(h) that it is necessary to share the bands in which the search is conducted with other Services;

that available technology will allow a search for these signals from the earth, from earth-orbit, and, eventually, from the moon and to minimize interference, certain locations on earth and in space may be preferred;

DECIDES that the following question should be studied:

what are the most probable characteristics of radio signals which might be broadcast by extraterrestrial civilizations and the technical characteristics and requirements of a system to search for them;

what are the preferred frequency bands to be searched and the criteria from which they are determined;

what protection is necessary for receiving systems conducting a search for artificial radio signals of extraterrestrial origin;

what criteria will make operation of a search system feasible in shared, adjacent and harmonically related bands of other Services;

6.

what are the preferred locations, on earth and in space, for a search system?

Addendum No. I to Volume II, XIIIth P.A. of the C.C.I.R., Geneva, 1974

COMPLEMENTARY DOCUMENT 10

RESPONSES TO A QUESTIONNAIRE SENT TO LEADING RADIO OBSERVATORIES

Prepared by:

Philip Morrison
Professor of Physics

Massachusetts Institute of Technology

RESPONSES TO A QUESTIONNAIRE SENT TO LEADING RADIO OBSERVATORIES

At the conclusion of the second full meeting of the Workshop, it was agreed to survey the directors of representative radio observatories on a number of matters where the apparent direction of SETI and the concerns of those observatories overlapped strongly, especially in the utility of wide-band simultaneous reception.

The following letter was sent to about 35 such directors from the published lists. Seventeen answers were received from organizations in the United States and in three other countries. The responses to the questions are summarized below; the identity of the respondents is filed in the records of the Workshop. One foreign response included an original contribution to the problem; several other responses included reprints and other valuable information.

Overall, we learned that there was not much unpublished work in SETI, and that most radio observatories could foresee some forms of cooperation between their ordinary scientific investigations and work on behalf of SETI.