The Senate extended its vocal range yet another dimension yesterday by holding a committee hearing in which the senators were in Washington and the witnesses were in Illinois.

A special space satellite connection, different from and potentially much more versatile than network television hookups, provided two-way color picture and sound communication between members of the Science, Technology and Space Subcommittee of the Senate Commerce Committee and eight witnesses in the courthouse at Springfield, Ill.

The witnesses gave their views on pending legislation to boost long-range weather and climatic change predictiins, and the senators watched them on three 25-inch television sets.

The hearing room audience normally has a good view of the senators, but sees only the backs of witnesses' heads. This time, it was almost reversed, with the monitors and three cameramen partly hiding the senators while two additional TV sets showed the Illinois witnesses to the audience.

Although the sound occasionally recalled a mushy airport loudspeaker and failed briefly altogether at one point, Sen. Barry Goldwater (R-Ariz.) said the picture quality was much better than in a televised international forum he participated in some years back. "That one nearly drove me crazy sitting there watching myself speaking and moving my lips a hundredth of a second behind," he said.

Dr. Robert S. Cooper, director of the Goddard Space Flight Center in Greenbelt, explained in an opening statement the makeshift setup did not need the enormous broadcast and receiving towers that television stations now require for long range transmission.

Instead, the Illinois end consisted of a mobile van the size of an interstate bus parked next to the Springfield courthouse, he said. The Washington end was a similar van up on blocks out at the Goddard center, which could have been brought onto Capitol Hill if the event had warranted it, Cooper said.

Yesterday, however, the proceedings were transmitted to Goddard by leased telephone cable, which was what had caused the briefs sound failure, he said.

Transmissions from both ends were made at "moderate" power levels to the National Aeronautics and Space Administration's new Communications Technology Satellite, which rebroadcast them at "very high" power back down to earth, Cooper said. The satellite was launched 18 months ago and is "parked" in a stationary orbit 22,300 miles above a point off the west coast of Ecuador, he said.

The 200-watt power of the satellite is 10 to 20 times more than is normally available from satellite retransmission, Cooper said later, and is the key to the procedure. The power is provided by a solar energy panel 50 feet long that extends out from the body of the satellite like a ladder.

The system, which is a joint project of NASA and the Canadian government, has been used on a shared-time basis for a series of experiments linking doctors in remote areas including Alaska with specialists in continental U.S. cities for consultation on difficult cases.

It provided educational broadcasts to 2,400 scattered villagers in India, "people literally in mud huts and out in open fields," Cooper told the hearing. The Indian government is "highly interested" in obtaining its own satellite to continue the program, he added.

"I expect this kind of communication will become ubiquitous in our country as the technology and the social impact of it become better known," Cooper said. He told reporters that George Washington University Prof. Frederick Wood of the Department of Sociology had been contracted by NASA to study the social effects of a year of experimental use and to monitor the costs.

Commercial or private broadcasters would have to buy their own satellite and terminal equipment at a cost as yet undetermined, Cooper said.

However, he said that three committee rooms in the planned expansion of the west fron of the capitol were being considered for permanently installed television equipment. "All that would then be required elsewhere would be roving mobile units out around the country and a small dish antenna on top of the building here," Cooper added. "Congress would then better be able to serve its purpose of getting closer to the people."

The witnesses in Illinois appeared unruffled by the unorthodox procedure and generally agreed that the legislation under review would aim them greatly in promoting advance knowledge of weather conditions.