SALISBURY -- When astronauts in space shuttle Discovery talk with ground controllers, amateur radio and astronomy buffs like Anthony R. Curtis don't have to wait for the evening news to find out what they said.

Using radio receivers often as simple as a common scanner designed to monitor police and fire calls, listeners can tune in.

They listen to frequencies carrying the chatter between the National Aeronautics and Space Administration's facility in Houston and the crew of six astronauts as they circle the Earth at 17,500 miles per hour.

Depending on the equipment used and the shuttle's location, what listeners hear can be surprising.

"Anything the astronauts want to talk about," said Mr. Curtis, an instructor at Salisbury State University who has written 72 books, many of them about space science and communications. "You can hear the serious stuff, such as astronauts describing some little bubbles in a jar or interviews with the news media."

Manned space missions like Discovery, which is scheduled to end its 10-day flight today, when it returns to Florida, excite amateur radio operators and schoolchildren.

They can listen to and often talk directly with the astronauts through a program called the Shuttle Amateur Radio Experiment (SAREX).

The project was launched in late 1983 as a NASA public service for amateur radio operators -- or hams -- and others in the United States interested in learning more about space exploration.

SAREX was part of the Discovery mission, and schoolchildren, including a class at Dwight D. Eisenhower Middle School in Laurel, spoke with

the astronauts through ham linkups with the shuttle craft.

Although two-way communications between astronauts and hams requires a space mission, there's still plenty of noise coming from beyond the Earth's atmosphere, said Mr. Curtis, whose latest book lists 2,200 frequencies that can be monitored by radio hobbyists.

Most of the signals in Mr. Curtis' "The Outer Space Frequency Directory," a paperback released this summer by Tiare Publications of Lake Geneva, Wis., are associated with man-made satellites and space probes.

But many are radio waves emitted by natural sources -- planets, stars and upheavals of heat and light in deep space.

"It's so cataclysmic in the heart of our galaxy," said Mr. Curtis, 53. "There's so much electromagnetic energy of all types -- radio signals, light waves, infrared heat, X-rays -- and all this stuff is coming out like a huge fountain of energy."

Tuning in most outer-space signals usually requires sophisticated radios and antennas, equipment too expensive or too difficult to build for most listeners but essential for amateur astronomers who find the pastime rewarding.

"It's a challenge to do these things," said Emil Pocock, a 48-year-old radio amateur who lives in Lebanon, Conn. "For people of my generation who grew up in the space age and who have built their own equipment, this is pretty exciting."

Man-made objects such as satellites send data to Earth constantly, although the sounds are unintelligible to the human ear.

"If you listen to these signals with a radio receiver, they sound like tones, beeps, gurgles and just about any kind of imaginable thing," Mr. Curtis said. "They are not human voices, but a variety of sounds. One needs a computer program to decipher them."

Natural space frequencies have their own audio characteristics. The Earth's sun, for example, sends signals that are picked up as whizzing noises, buzzes and hisses, Mr. Curtis said.

Being able to discriminate between static background noise and sounds from outer space takes time, Mr. Curtis said. But after the ear is trained, serious listeners feel a sense of achievement.

"They get the rush of excitement of knowing that they themselves are able to participate in the technology and just to hear something that is so far away that it takes 45 minutes for the radio signal to get here by the speed of light," Mr. Curtis said. "It's not so much what it sounds like as it is the act of being able to tune in."

Robert E. Bruniga, a retired Navy commander who oversees the U.S. Naval Academy's satellite ground station in Annapolis, is a longtime ham who tuned in but was turned off.

"Anything that's not man-made, to me, is noise," he said.

Mr. Bruniga, who is regional technical coordinator for the 160,000-member American Radio Relay League, said he listened the signals from this summer's comet crash into Jupiter and was not impressed.

"I found it to be the most boring thing in the world," he said. "But then that's just not my bag."

More popular among the 600,000 hams in the United States is the SAREX project, which enables individuals to make direct contact with astronauts more than 200 miles above the Earth.

Scanner and shortwave eavesdroppers normally tune to signals coming from an antenna at NASA's Goddard Space Flight Center in Greenbelt. What most listeners hear is a live retransmission of talk between NASA and astronauts.

The transmission from space originates from the shuttle and is picked up by one of several Tracking and Relay Data Satellites. The signal is received by a NASA facility in White Sands, N.M., where it is sent to another communications satellite and then to Goddard. From Goddard, the signal is sent to Houston and, at the same time, retransmitted by the SAREX antenna in Greenbelt.

James H. Blackwell, a NASA employee and president of the Goddard Amateur Radio Club, said listening to retransmissions of the astronauts' chatter is growing in popularity, especially among shortwave radio enthusiasts.

"We get letters from people all over the world who listen," he said. "People who aren't even hams."

WANT TO LISTEN?

Police scanners and shortwave radios can pick up frequencies used for retransmitting communications between space shuttle

astronauts and NASA ground control.

SCANNERS

* 147.450 MHz. A retransmission from the Goddard Amateur Radio Club's facility in Greenbelt. The best reception is within a 40-50 mile radius, although signals often can be heard outside Maryland.

* 145.550 MHz. Unedited down-link from astronauts to Earth used primarily for Shuttle Amateur Radio Experiment communications. The best reception is when the shuttle is directly above the radio receiver.

SHORTWAVE RADIO

NOTE: All are retransmissions from the Goddard Space Flight Center.

* 3860 KHz (lower side band)

* 7185 KHz (lower side band)

* 14295 KHz (upper side band)

-! * 21395 KHz (upper side band)