"All have been just small little stabs in the dark," Tarter said. "We haven't yet begun to look."
Tarter said it was "very timely to begin a systematic search" for signals
from outer space. She said that prototype equipment capable of monitoring 74,000 radio frequencies for signals has been developed at Stanford University and has been used for the last year in Goldstone, Calif.
She said this equipment was developed under a NASA-sponsored five-year research and development program costing $1.5 million a year. She said she would like to see Congress authorize $77 million requested by NASA to begin a systematic 10-year search in 1990.
The effort to find other life in the universe assumes that advanced civilizations emit signals either through "leakage" from radio, television or radar broadcasts on their planets or through specific attempts to communicate with other worlds.
Tarter said that astronomers would soon have the ability to track and analyze 10 million different radio frequencies for signals from other civilizations. Under the proposed NASA program two different methods would be used to search for signals from outer space.
In the first method, astronomers would utilize the largest radiotelescopes available, such as the 1,000-foot diameter dish of the Arecibo Observatory in Puerto Rico, to search for signals from 800 nearby stars similar to our sun.
They would look for relatively weak signals in a narrow range of frequencies that are either emitted continuously or repeated periodically.
In the second method, astronomers would use 112-foot-diameter antennas at three NASA tracking stations to scan the entire sky for stronger signals. They would look over a much broader range of radio frequencies.
Tarter acknowledged that there might be other civilizations that have not developed advanced technologies capable of emitting radio signals. For example she said there could be other worlds "that are covered with water and populated by animals similar to dolphins and whales that swim in the water." John Rather, a vice president with Kaman Aerospace Corp. in Arlington, Va., said attempts should not just be limited to scanning the heavens for radio transmissions. He said it was very possible that other worlds might attempt to communicate by using advanced high-powered lasers.
He said that lasers could transmit far more information than radio waves and could be directed far more accurately. "The laser alternative must be taken seriously," he said.
Rather sketched several possible ways that an advanced civilization could attempt to make contact with other worlds including placing thousands of lasers in orbit around a planet such as Mars or covering a planet similar to Mercury with solar-powered devices capable of emitting laser beams.
Some scientists raised the possibility that we might not be able to understand the messages sent out by other worlds.
But Tarter said that wouldn't bother her. She said she would be satisfied just to detect communications from other civilizations. "Because then we would have answered the question: Is there life elsewhere in the universe," she said.