The news that day 25 years ago took this city by storm. Children were let out of school, crowds gathered in the streets. For the first time, a human being had gone into space, and he was Soviet cosmonaut Yuri Gagarin.

"I can just remember the feeling of pride, of excitement. It was a real national holiday, something spontaneous," recalled one Muscovite who was then a 15-year-old schoolgirl.

This year, the Soviet Union is using the anniversary of Gagarin's flight to stage a full-fanfare celebration of its space program and its recent string of successes -- from the recent probe sent to Halley's Comet to last summer's daring rescue of a disabled space station.

Tonight the city was treated to a fireworks display in honor of Cosmonauts' Day. For the last week, the newspapers and television have been full of commemorative articles and films glorifying cosmonaut-heroes and their missions aboard a dynasty of Vostok and Salyut spacecraft.

And some of the secrecy that has traditionally surrounded Soviet space efforts has been lifted. Foreign reporters have been taken on tours of the mission control center outside Moscow and of Star City, a town of 3,000 where a corps of 50 Soviet cosmonauts live andtrain.

Even the Soviet press has been more frank about once shrouded aspects of the program -- disclosing the death in 1961 of a cosmonaut in training, and providing new, often vivid, details on the selection and prepartion of the 60 Soviet cosmonauts who have gone into space.

But above all, the 25th anniversary has given the Soviet Union an opportunity to tote up its list of recent successes in space and, in the view of some observers, draw an inferential comparison with recent setbacks to the U.S. space program.

From the beginning in 1957, when the Soviet Union launched Sputnik, the fate and the pace of the two space programs have been linked. Sputnik set off frantic catch-up efforts in the United States, while in 1969, after the U.S. moon landing, the Soviet program looked as though it had been left behind.

Overall, most western scientists give the Soviet program high marks for its steady pace and its focused pursuit of the goal of permanently manned space station.

The February launch of a third-generation model -- the Mir, or "peace" station -- gives the Soviets new flexibility for scientific experiments in space, and new opportunities for setting endurance records.

The Soviets have also scored successes with unmanned planetary missions, notably the Vega I and Vega II probes of Venus and then Halley's Comet. A launch of a craft to Phobos, the larger of Mars' two moons, is planned for 1988 and an asteroid probe for 1990.

In these areas, American efforts appear to lag: A U.S. probe to Mars is scheduled two years later than the Soviet one, and an American space station is not expected until the mid-1990s.

"Each one must go its own way," philosophized cosmonaut Alexei Leonov recently.

Scientists on both sides are pursuing the idea of joint projects -- particularly to Mars. But a joint space agreement, which lapsed in 1982, has not been renegotiated and U.S. officials say it is now held up by Soviet objections to the Strategic Defense Initiative program.

While showing new confidence, characterized by the new openness, the Soviets still have a tendency to look over their shoulders at the American program -- and make either direct or inferred comparisons.

The explosion of the shuttle Challenger in February was met here with official expressions of sympathy. But some of the recent articles about space have pointedly emphasized Soviet safety efforts, and sermonized on the dangers of trying to push space flight too fast.

However, accounts of the early days of the Soviet space program, when the legendary Soviet rocket specialist Sergei Korolev was known simply as the "chief designer," show that then-Soviet leader Nikita Khrushchev frequently intervened to push the program along.

Western analysts here also note that while the new openness has cast a little more light on the history of the Soviet program, much of it is still kept secret, in particular anything to do with failures and accidents.

The disclosure of the death of Valentin Bondarenko in a fire in 1961 puts the number of disclosed deaths in the Soviet program at five. But there is evidence of other accidents. For instance, a disastrous explosion on a launch pad in Kazakhstan in 1960, which allegedly killed dozens of people including a Soviet field marshal, was confirmed in Khrushchev's memoirs. But the so-called Nedelin accident never has been mentioned in the Soviet press.

Still, the director of the cosmonaut training center at Star City recently conceded that not disclosing such events as Bondarenko's death in 1961 may have been a mistake. "It wasn't publicized. I don't think that was correct. But at that time, we were only at the starting point of a long run," said Georgi Beregovoi.

The launching of the Mir station in February, and subsequently of a two-man crew, marks the other end of the long run.

The new station, expected to have a lifespan of about 10 years, has the capability to dock six craft at a time -- four modules carrying scientific experiments and two supply ships.

This flexibility, which should be put to full use next year, is expected to make work and life on board the 20-yard-long station easier, and set the stage for new records on human endurance in space.