When French scientist Jacques Blamont visited the Goddard Space Flight Center in Greenbelt, Md., 11 years ago, he dreamed of a sphere pulsating inside a star.

"I woke up that night and said, 'Of course, a balloon on Venus,'" Blamont recalled last week. "And that's how the idea was born. I swear it, even thought I had never thought of exploring Venus before in my life."

Blamont, now France's chief space scientist, is the architect of what is planned to be the next mission to Venus, a joint venture by France and the Soviet Union in 1983 to put two balloons into the mysterious sulfuric acid clouds that circle the entire planet and perpetually obscure its surface.

Blamont is here at the Ames Research Center as a guest of the National Aeronautics and Space Administration to listen to the Pioneer science team assess its performance on Venus. The information will help him plan the balloon mission.

Venera 83, as the joint mission is called, marks the first time France has had a role in planetary exploration, so far the sole province of the United Soviet Union.

Blamont first offered the ballon mission to the United States, less than a year after he had his dream. When the United States was not interested, he offered it to the Soviets but they, too, showed little interest. Then, in 1972, two soviet spacecraft flew through the clouds of Venus for the first time and the attitude changed.

"They came to me and revived the whole thing," Blamont said. "By this time, the United States was committed to the Pioneer mission but the Russians said: Let's talk about the balloons.'"

Blamont believes that one of the few areas where the four Pioneer probes were weak is what he calls the "dynamics" of the sulfuric acid clouds, the updrafts, side winds and downdrafts that must be churning them.

"We haven't decided but we are thingking of carrying two instruments to measure the vertical and horizontal wind changes in the clouds," Blamont said. "We don't have much time because the Soviets want to freeze the instrument design at the end of January."

At a cost of $20 million, France is building the two 27-foot-high balloons. The Soviets will supply the rockets that will carry them into the clouds and two spacecraft that will orbit Venus and serve as radio relays to Earth.

France is supplying the 66 pounds of instruments for each balloons and is furnishing some of the 170 pounds of instruments that will be aboard each of the orbiters. Among the instruments France will make for the obiters is an ultraviolet telescope to measure the chemical makeup of the Venrian stratosphere and the tops of the clouds.

The balloons will consist of five layers of plastic, the outmost and innermost to be made of Teflon to resist the corrosive sulfuric acid clouds. Blamont said the most difficult part of making the balloons has been finding a glue to hold the five layers together.

The balloons will be sent down into the atmostphere in metal spheres, enter the clouds.

The balloons will start inflating will start inflating with helium at a height of 37 miles, then fall seven miles to the bottoms of the clouds when they become fully inflated and rise into the clouds where they will rest at a height of 35 miles.

"We'll be floating right in the middle of the clouds," Blamont said, "right where Pioneer instruments found not only what appears to be sulfuric acid but also solid particles of free sulfur."

Since the winds on Venus blow from day toward night, they will carry the balloons away from the night side and back toward the sunlitside of the planet. Blamont figures the balloons will go from night to day in four days, which is none too soon because he thinks the acid in the clouds will chew through the skin of the balloon in six days.

"We will not make a full circle of the planet," Blamont said. "If we get the balloons into the clouds in the early part of the night side, we should be able to cover three-quaters of the planet."

Unlike most Soviet missions to the planets, the scientific results of the balloon flight around Venus promise to berevealed to the entire scientific world. This could be the reason why the U.S. space agency is cooperating so heartily with the French. As for Blamont, he sees it all just a little differently.

"This has been the only possibility for French scientists to go into the planetary program," Blamont said. "There are some individuals like me who have had instruments on U.S. spacecraft but we'd like to have a larger constituency and the only way for our scientists to go to the planets is through this cooperation withthe Soviets."