Konstantin U. Chernenko has reappeared in public, restaking his claim to the Kremlin leadership. An appearance on Soviet television, in which he presented awards to three cosmonauts, was apparently aimed at quashing speculation over his health after a seven-week absence from public view.
The fact that such a key figure can drop from sight for so long without official explanation is testament to the secretive nature of the Soviet government. Moreover, Mr. Chernenko returns to an international and domestic situation even more complicated - and, from the Kremlin's perspective, frustrating - than when he departed from Moscow in mid-July.
Western Kremlin-watchers assume that Chernenko was on vacation in the Crimea, in the southern USSR, for at least part of the last seven weeks. There were unconfirmed reports that he returned early, and by some accounts was hospitalized here in Moscow.
(In footage broadcast on the evening television news, the Soviet leader appeared slightly tanned, and was shown walking slowly but steadily. He held the pages of his five-minute speech close to his face and read stiffly in a soft, clear voice, the Associated Press reported.)
The Kremlin had telegraphed word of his reappearance through reports in the West by Soviet journalist Victor Louis, and through accounts of the ceremony on Radio Moscow and Tass, the official Soviet news agency.
The appearance may have been calculated to scotch growing rumors of Chernenko's ill health circulating not only among foreign diplomats and journalists but ordinary Soviet citizens as well. And in this society, even rumors are weighed carefully in the political balance.
Said one Soviet woman, ''We would not be surprised if he is having difficulties. He is, after all, nearly 73 years old. But we did not expect them so soon'' after taking office.
Indeed, most Kremlin-watchers say Chernenko has not yet made his imprint on the Kremlin bureaucracy - a process that some Soviet analysts say could take as long as five years. Chernenko - who apparently has breathing difficulties and a history of health problems - obviously does not want the process delayed.
Still, there are mixed signals as to his effectiveness in office thus far. Many Western analysts, for example, have concluded that authority for foreign policy decisionmaking has virtually been ceded to veteran Foreign Minister Andrei Gromyko. Proffered reasons vary - from Chernenko's lack of foreign policy experience to a possible lack of political clout or even to incapacitation.
Whatever the reasons, the Kremlin seems to have lurched into something of a foreign policy quagmire. Soviet officials have doggedly demanded the removal of new medium-range NATO nuclear missiles deployed in Western Europe last fall - without any apparent success. The Soviets have made no moves to restart negotiations aimed at limiting ground-based nuclear weapons, continuing to blame the United States for the failure of such talks.
Also, the Soviets seemed to have crossed wires on negotiations on space-based weapons, first proposing such talks and then backing out - all the while blaming the US.
Chernenko, however, used his public reemergence to make yet another pitch for starting negotiations on space-based weapons. Yet he indicated no change in Soviet attitudes, instead calling upon the US to ''display political foresight and appraise the Soviet Union's constructive approach at its true worth.''
Soviet criticism of US policies, however, has thus far apparently had little impact on one intended audience - American voters - during this US presidential election year. President Reagan, whom the Soviets want desperately to depict as a dangerous militarist bent on conflict, enjoys a substantial lead in opinion polls.
Meanwhile, there are signs of disquiet in the Soviets' own camp. Maverick Romania refused to join in a Soviet-led boycott of the Los Angeles Olympics. And East German leader Erich Honecker seemed bent on making a controversial trip to West Germany, despite blunt criticism in the Soviet press over growing ties between the two Germanys. The trip was canceled even as final details were falling into place, and Western analysts attributed that to heavy pressure from Moscow.
Indeed, some analysts say that such public displays of disunity in the East bloc could only happen if there were something of a power vacuum in Moscow itself.
At home, the Soviet economy continues to perform at about the same lackluster pace as in recent years. There are signs that this year's wheat harvest could be a disappointment. And Soviet oil production has dipped slightly - with potentially serious implications for the country's long-term trade prospects.
It all adds up, in the view of Western analysts, to a challenge that would be daunting to any Soviet leader, regardless of his age or health. Confirmation that Chernenko is on the job is a prerequisite to tackling these formidable domestic and foreign problems. Beginning to solve them is, of course, quite another matter.