An unmanned Voyager spacecraft survived what was apparently a hard ride away from earth yesterday and was winging its way to Jupiter and Saturn, where it will make the most detailed observations ever taken of the two largest planets in the solar system.

If won't be until March, 1979, before Voyager reaches Jupiter, but when it does it will aim 11 scientific cameras and instruments at the giant planet and its four largest moons. Using the enormous gravity of Jupiter to give a boost. Voyager will then fly to Saturn, where it will arrive in August, 1980, to photograph and map the solar system's second-largest planet, its dazzling and mysterious rings and the only moon in the solar system that looks more like a planet.

For a while yesterday it appeared as if the 1,800-pound Voyager had been given such a hard liftoff from Cape Canaveral, Fla. by its Titan Centaur rocket that it might be flying to Jupiter and Saturn without its five most important instruments deployed away from the spacecraft.

The first signs reaching earth were that the six-foot-long instrument boom was jammed against the side of the spacecraft. If this were the case, the television cameras and ultraviolet and infrared telescopes that are strung along the boom and are to make the most valuable observations of Jupiter and Saturn would be useless.

"At the present time things do not look too good." Voyager project manager John R. Casani said about 90 minutes after the spacecraft left earth. "I would say at this time that the spacecraft is in trouble."

Frowns turned to smiles less than two hours later when it became clear that the boom was deployed at least most of its length and possibly its full six feet. Voyager scientists knew this was the case because temperatures along the boom were what they expected them to be if the boom was deployed and sitting out in the sun away from the spacecraft.

"The boom may have swung out and then stopped prematurely before it locked into place," said Ron Draper, spacecraft systems engineer at the Jet Propulsion Laboratory in Pasadena, Calif., where Voyager was built and from where it will be controlled. "But we do know it's most of the way out and may be all the way out."

There was some concern that the boom might be flopping around in a partly deployed state, but Draper said this was hard to imagine because the springs that deploy it also hold it stiffly in place at any stage of deployment.

"We'll know more about where it sits tonight or tomorrow," Draper said late yesterday. "If the boom is not fully deployed we can still get our pictures and observations and there are some maneuvers we can make in the next few weeks to get it fully deployed. I'm not worried."

Voyager will travel a curved course through space in the next 18 months wthat will take it 681 million miles to Jupiter, which today lies in a straight line 510 million miles from earth.

The spacecraft's primary mission is to obtain photographs and measurement of the turbulent atmosphere on Jupiter, which is so big it dwarfs everything else in the solar system and so dynamic it spawns cyclones and hurricanes that last for hundreds of years.

"It's one big destructive force, with permanent storms on its surface." Voyager project scientist James E. Long said.

Voyager also will get the first closeup pictures of the four largest of Jupiter's 13 moons - Ioio, Ganymede, Callisto and Europa.The last two are covered with crusts of water ice and these photographs will reveal what heavenly snowballs look like after they have been bombarded through time by meteorites.

From Jupiter, Voyager will speed on to Saturn fly below its magnificent rings and take the first pictures of its giant moon, Titan, which has the only measurable atmosphere of any moon in the solar system. Titan's atmosphere is at least 10 times denser than the atmosphere on Mars and strongly resembles what scientists believe the earth's atmosphere looked like 3 billion years ago.

A second Voyager in the $390 million program is due to leave earth Sept. 1 but may be delayed while engineers study whether the Tital Centaur liftoff yesterday was a little too rough.

The second Voyager will fly to Jupiter on a different path than the first and will examine Jupiter's inner-most moon, Amalthes, to see how it survives the huge pull of Jupiter's gravity. The second spacecraft also will go on to Saturn, but on a flight path that will put it on a direct line to Uranus, the next planet out in the solar system, where it will arrive in 1966.