MOSCOW, SEPT. 29 -- Soviet television viewers turned on their sets tonight to see Soviet leader Mikhail Gorbachev back at work after an uncharacteristic 52-day absence from public view.

Looking tan, slimmer and in good humor, he was shown talking to a visiting French delegation. "I believe there has been some suggestion that I have taken too long a holiday. I can tell you I earned it," he told them, according to the official news agency Tass.

Gorbachev's energetic performance today cut short some of the wilder rumors that had circulated here about his health, but it served to highlight once again the powerful impact of the leader's image in this autocratic society.

It also showed that despite calls for more "openness" in society, the Kremlin has not yet allowed the light of glasnost to shine on its own internal doings, least of all on the leader's personal life.

Official assurances given to western reporters over the past week that Gorbachev was on vacation and in good health were not presented to the Soviet public. The silence, punctuated only by articles and messages in the press signed by Gorbachev, left people here wondering and fueled rumors that Gorbachev was ailing, or worse.

Coming at a pivotal moment in Gorbachev's campaign for economic and social reforms, his absence was seen by some here as troubling. Many noticed that as Gorbachev's voice fell silent, others -- such as Yegor Ligachev and KGB chief Viktor Chebrikov -- filled the vacuum, striking a conservative note on cultural themes.

Gorbachev took the opportunity of his remarks to the French delegation today to affirm his political strength. "There is no political opposition in the Soviet Union," he said, adding that "restructuring is gathering strength."

But, echoing remarks by Chebrikov earlier this month, he warned against the "vain aspirations" of those who seek to use the new "openness" in Soviet society to instigate "social and political upheaval." Among the volatile Moscow intelligentsia, Gorbachev's absence rapidly became the subject of kitchen debates, spawning everything from medical theories to speculation about the political future of the country.

Last year, during Gorbachev's vacation, similar rumors spread through Moscow, some speculating wildly about possible attacks on Gorbachev or his wife, Raisa.

Rumors have long been part of the Moscow scene, but the key ingredient and cause for anxiety in each case has been the leader's lack of visibility. Distrust of official explanations persists. It was not long ago that Kremlin spokesmen were blandly telling western reporters that leaders had colds when events later proved that they were dying.

It may never be known why Gorbachev, one of the most communicative Soviet leaders in history, absented himself this year for such a long period. Last year, he broke his announced vacation for publicized stops at a children's camp and a provincial capital. This time, reports persist that either he or Raisa was ill and had recovered.

By his own explanation today, he left for vacation on Aug. 24, more than two-weeks after his last public appearance, on Aug. 7.

A theory presented by Soviet sources is that after a steady run of public appearances, Gorbachev decided to adopt a low profile to avoid overexposure and curtail any signs of an incipient personality cult.

"For us, a personality cult is a very dangerous thing, something we know from our history," said one Soviet official. "I think Gorbachev is very aware of this."

For a Soviet leader, the importance of being seen has to be balanced with the importance of not being seen too often. During the past year, some people began to complain that Gorbachev talked too much. His public utterances -- whether on the sidewalks of Riga, in his Kremlin offices or in formal speeches -- are usually broadcast in full, sometimes taking up more than an hour of the evening television news. On the following day, newspapers carry the full text.

Gorbachev's last television appearance, Aug. 7, was a rambling half-hour conversation with a group of Russian teachers from the United States, which served as little more than a showcase for his telegenic style.

The danger of abusing the pulpit that goes with the general secretary's office is particularly sensitive now that, as Gorbachev keeps repeating, the task of "restructuring" requires not words, but deeds.

Today, meeting with the 370-member France-U.S.S.R. Friendship Society, Gorbachev used his relaxed, garrulous style to deflect the issue of his absence. He said his leave had been a "fruitful" one, giving him time to finish a book and prepare a major speech for the Nov. 7 celebrations of the 70th anniverary of the Russian Revolution.

Gorbachev's speech tonight, made without notes, undercut suggestions that the Soviet leader had lost strength or confidence. But some of the issues raised during his absence still linger.

While Soviet spokesmen publicly professed dismay at the unseemly questioning from western reporters about Gorbachev's whereabouts, one Soviet official indicated privately that the episode had been another lesson for the Kremlin's developing sense of modern press relations. "We are still learning," he said.