ANDREI Sakharov returned to Moscow yesterday after almost seven years' internal exile, prepared to resume a life of scientific research and human rights agitation. His release appears to be another forceful attempt by Soviet leader Mikhail Gorbachev to convince a skeptical Western world that the Soviet Union is changing.
It will also intensify pressure on the Kremlin to change its policy on dissent: Dr. Sakharov's presence in Moscow will keep attention on the remaining cases of imprisoned dissenters.
But it also seems to be a signal to the Soviet people, particularly the elite, that criticism and intellectual debate - qualities Mr. Gorbachev's supporters say are crucial to the Soviet Union's rapid development - are now permissible.
``I am going home to rest a little. Then I am going to a seminar at the Physics Institute of the Academy of Sciences where I work,'' Sakharov told journalists at the station where he and his wife, Yelena Bonner, arrived after an overnight train ride from banishment in Gorky. A theoretical physicist who was one of the developers of the Soviet hydrogen bomb, Sakharov is now being given the chance to resume the highly privileged life of a full member of the 800-strong Academy of Sciences.
His commitment to human rights appeared undiminished. The 1975 Nobel Peace Prize winner spoke of his feelings of ``joy and excitement'' at being back in Moscow, but referred to the ``tragic fate'' of his friends in camps and prisons.
``I cannot for a moment free myself of the feeling of horror at the martyr's death of my friend Anatoly Marchenko in the struggle with injustice.'' The death of Marchenko, a prominent Soviet political dissident, was reported to his wife Dec. 9.
``I hope that my liberation will somehow help to resolve ... the problem of prisoners of conscience and other painful problems standing before our country and the world.'' The decision to release him, Sakharov said, ``is a very small part of what must happen. There has to be a fundamental political decision'' on this, he added. ``It's vital.''
He would continue to speak and write on human rights, he said. ``That is my fate.'' Asked if he would be willing to live abroad, he said that the question did not apply in his case, ``because of my secrets. But perhaps I am mistaken.'' If the government should allow him to go, he added, ``I am ready to go.''
Sakharov, who was in poor health for much of his time in Gorky, said he was in ``average'' condition. He was banished to the city, which is closed to foreigners, in January 1980, without charge or trial, after protesting the Soviet invasion of Afghanistan. His wife, condemned in 1984 to four years' exile in Gorky, arrived with him, but slipped away to the car while he spoke to reporters. ``She is a sick person,'' he said.
The phone call from Gorbachev last Thursday that announced his release was completely unexpected, Sakharov said. Quoting briefly from the conversation, he seemed to be poking light fun at the bureaucratic jargon in which Gorbachev conveyed the message.
``He said a decision had been taken that I could return to Moscow,'' Sakharov told journalists, ``and Bonner will also be able to return. I said: `That is my wife.'''
Journalists outnumbered ordinary Russians waiting to meet the train when it pulled into the cold and still-dark station at 7 a.m.
No policemen and few, if any, security men were in attendance.
Curious bystanders joined the slow-moving informal press conference as it made its way down the platform and over to the parking lot. Sakharov's imminent release had been announced in the Soviet press, though the date of his arrival had not.
Several expressed delight when they heard who it was. Two teen-age boys, aged 17 and 18, said they had never heard of him. Told he had been in Gorky for seven years, one of them commented that this was ``way back.'' Looking at the TV lights, he remarked, ``He must be an important bird.''