Moscow — The Soviet Union is being run by an invisible man, but a man who still appears to be exerting strong control. Soviet leader Yuri Andropov failed to appear at an important meeting of the Central Committee of the Communist Party, which took place Monday. There is the possibility that he could show up on the second day of the plenum Tuesday, or at the Supreme Soviet session on Wednesday.
Still, his absence has reignited speculation over the true state of his health - and over his long-term future at the helm of the Soviet Union.
Despite his absence, some of Andropov's supporters apparently gained in influence within the party. One Western diplomat observed that the year-end plenum of the Central Committee seems to have proceeded ''just as it would have had Andropov been there himself.'' A speech by Andropov was read in his absence.
According to Tass, the official Soviet news agency, Andropov ''expressed his deep regret that because of temporary causes he was not able to attend the session of the plenum.'' There was no explanation of what those ''temporary causes'' might be.
Andropov's continued influence was evident in the elevation of various party officials during the plenum. Viktor M. Chebrikov was elevated to alternate membership in the Politburo of the Central Committee, the country's most powerful organization. Chebrikov is head of the KGB (the Committee for State Security), and a trusted confidant to Andropov.
Formerly KGB head, Andropov apparently hand-picked Chebrikov to take over at the KGB. One diplomat noted that it was not at all unusual for the head of the KGB to move into the Politburo.
Still, Western observers were intrigued by the elevation of Yegor K. Ligachev , who became one of the secretaries of the Central Committee. His rise in the party heirarchy apparently signals another step in Andropov's consolidation of control over the Central Committee. Since coming to power last year, Andropov has had something of house-cleaning of the Central Committee secretaries - either removing or demoting supporters of former leader Leonid Brezhnev.
Two other alternate members of the Politburo, Vitaly I. Vorotnikov and Mikhail S. Solomentsev, were elevated to full membership in the Politburo. Both are thought to be Andropov supporters.
Still, no matter how skillful Andropov and his supporters might seem at behind-the-scenes organizing of the plenum, it remains to be seen whether he can stay on top in the Soviet Union.
One diplomat noted that it was unusual for Tass to report Andropov's absence. In his view, this probably was done to prepare Soviet citizens for not seeing Andropov at Wednesday's meeting of the Supreme Soviet.
The Supreme Soviet, roughly analogous to a parliament, mainly rubber-stamps decisions made beforehand by the Central Committee. But, unlike the Central Committee, the Supreme Soviet meets in public. Andropov is chairman of the Supreme Soviet and would be expected to chair the meeting. Thus, his absence will be particularly evident.
This may not be the first time a general-secretary of the Central Committee of the Communist Party has failed to appear at a plenum. There are unconfirmed reports that Leonid Brezhnev did not appear at one during the mid-1970s.
But that was when Brezhnev's grip on power was unquestioned. Western diplomats speculate that Mr. Andropov's health problems must be serious indeed to have kept him away from the plenum - far more serious than the ''cold'' that the Kremlin says is keeping him indisposed.
Inevitably, speculation has once again been fueled among Western observers as to whether Mr. Andropov will be anything more than a transitional leader. Some diplomats already suggestthat he is ''on the way out.''
The text of the Tass reports and Mr. Andropov's speech were read on the evening television newscast. There was but a single line noting his absence.
But even before the plenum, Soviets were beginning to wonder what was really happening inside the Kremlin.
''It is rather ridiculous,'' said one Muscovite, ''to have a leader that one cannot see.''
In his speech, Mr. Andropov dwelt on the state of the nation's economy, and hewed to themes that are by now familiar: hardwork, discipline, better planning, and better management.
Still, the speech seemed to have been written by a man who still plans to make an impact on the Soviet Union.
Andropov laid particular stress on clearing up ''bottlenecks'' in the economy that were impeding growth. Labor productivity could be improved in many sectors of the economy, he said. And he chastised bureaucrats who he said were resisting modernization.
''Some industries are marking time and failing to fulfil plans to introduce new equipment,'' said Andropov.
''The key to success'' in many areas of the economy, he said, ''is in raising the responsibility of the personnel and strictly demanding from them an irreproachable execution of their duties.