Hindsight in Kremlinology is no guarantee of 20-20 foresight

* The new Soviet leader is ''very much in charge,'' said Vice-President George Bush. There was ''reason to be hopeful'' that there might be a change for the better in United States-Soviet relations.

* The new Soviet leader seemed to be acting with ''full authority,'' Mr. Bush commented. There was agreement ''about the need to place our relations on a more constructive path.''

The Vice-President was certainly consistent. The problem, however, is that he was talking about two different men.

The first comments were about Yuri Andropov, who presided in the Kremlin as US-Soviet relations plunged to a new low. And, as subsequent events showed, Mr. Andropov's hold on power was not too tight - at least not strong enough to assure that he would be replaced by one of his own loyalists once he passed from the scene.

The second set of comments was made about Konstantin Chernenko, who took over from Mr. Andropov last week as the sixth leader of the Soviet Union.

It is, of course, possible that Mr. Bush could yet be proved right about Mr. Chernenko. However, his strikingly similar comments - made 15 months apart - illustrate how much the West relies on snap impressions and ''conventional wisdom'' about the Kremlin hierarchy. And, at least in the case of Andropov, it shows how such quick judgments can be wrong.

With the benefit of hindsight, it is possible to draw a few conclusions about the way in which the Soviet leadership transfers power, the way in which Western diplomats and the foreign press interpret the process, and the mistakes that are made along the way.

1.Official Soviet statements about the well-being of the leader can hardly be trusted. Throughout the course of Andropov's illness, the Kremlin never announced that he had anything more serious than a cold or ''chill.''

In a speech in late December, Andropov regretted that he was unable to appear at a party gathering ''for reasons of a temporary nature.'' In fact, Andropov had been receiving treatment for a serious kidney ailment for a year before his death.

Nevertheless, less than two weeks before his death a Kremlin spokesman assured reporters that he was recovering and would soon reappear. After his death, and as if to prove its own deception, the government issued a detailed medical bulletin going into clinical detail as to the nature of Andropov's ailments and the treatment he received. Why?

Some analysts think the reason is to reassure the Soviet populace that the leader died of medical complications, and was not the victim of treachery.

2.The succession process in the Soviet Union clearly has the potential for instability, yet twice in recent times it has assured fairly smooth transitions of power.

The Soviet Union leaves few things to chance. Even the mourners that filed past Andropov's coffin were handpicked. But it does leave one key question unanswered until the last minute: Who takes over at the death of the leader?

There is no constitutional mechanism for naming a successor. Instead, the Communist Party must convene its nearly 300-member Central Committee for a meeting to ratify the choice of the ruling 18-member Politburo. In the middle of a Soviet winter, this proved to be a time-consuming process this time. The new leader was not named until nearly four days after the death of the last one.

Also, the process certainly gives rise to the possibility of a power struggle between opposing factions in the party.

Nevertheless, for the second time in 15 months, the Soviet leadership was able to engineer a fairly smooth transition. Last time, it appears that transfer was done in spite of the Central Committee, which was apparently only asked for pro forma approval of Andropov after his ascension was a fait accompli. This time, Chernenko apparently took pains to have the Central Committee involved, perhaps as a reassurance to party stalwarts that he would protect their interests in the future after some fairly rough treatment at the hands of Andropov.

At any rate, the process went fairly smoothly. The government and the country kept functioning. There was no crack in the party's facade of unity. And the transfer apparently went off without a hitch - even while the government and party were preoccupied with Andropov's funeral.

Some analysts say this will be the last smooth transition for awhile because it is probably the last time the party's ''old guard'' will be able to dominate the proceedings. That remains to be seen.

3.The West knows very little about the men who run the Kremlin and their relationship to one another. Most Western diplomats freely admit this. But leadership transitions make the point even more strongly.

Even days before the transition itself, the conventional wisdom was that Konstantin Chernenko had been edged out of influence months ago by Yuri Andropov and his supporters. Two younger men -52-year-old Mikhail Gorbachev and 61 -year-old Grigory Romanov - were rated as front-runners, with Chernenko a somewhat distant third.

The reasons for this misapprehension are varied. In some measure, it was the result of applying Western values and logic to a non-Western society. But, for the most part, it reflected a paucity of reliable information about the Kremlin leadership. That, in turn, is a result of the Kremlin's near obsession for conducting its affairs in secret. And Western analysts can hardly bear the blame for that.

4.It is difficult to overestimate the Communist Party's innate conservatism and respect for tradition.

Twice in the past, the honorary head of the commission planning a past leader's funeral has gone on to become the leader himself. This time, when Chernenko was named to head the commission, some Soviet citizens saw that as a tip-off that he would be the new leader.

''We knew it would be he,'' said one woman shortly after the announcement. ''We were not surprised.''

Many Western observers were not so sure. Even until hours before the announcement, they held out the possibility that precedent would be broken. It was not.

Chernenko had obvious liabilities. At age 72, he is the oldest man to take over as Soviet leader. His years spent in the shadow of former Soviet leader Leonid Brezhnev prevented him from building much of his own political base. He lacked practical experience or training in economic matters.

Yet the party chose him - largely, it appears, because he is a traditional party loyalist. He has never advocated bold new programs or major innovations. On the contrary, he has hewed closely to communist orthodoxy, calling for greater discipline. Moreover, he has evidenced a distrust of things foreign or religious.

It appears that is what the Soviet leadership wants in 1984. Convictions that major change is in order in the Soviet Union appear to be much greater outside this country's borders than within them.

5.Pronouncements made early in a Soviet leader's tenure may often be wrong.

Yuri Andropov was said to be a ''closet liberal'' who might ease up on repression at home and steer the way toward a lessening of East-West tension. He was not and did not. The Andropov era was marked by a continued crackdown on dissidents and religious activists at home and decline in relations with the West.

Chernenko is depicted as a traditionalist, the ideological offspring of Leonid Brezhnev. Interestingly, however, he has yet to summon up the name of Brezhnev in his public pronouncements since becoming general secretary.

Many analysts would be surprised if he didn't follow in Brezhnev's footsteps. But, then, in Kremlinology, the fact that there are no surprises is often a surprise in itself.

Perhaps the definitive word on the subject came from West German Chancellor Helmut Kohl. After he returned from Moscow, where he had attended Andropov's funeral, he admitted, ''I am not a Kremlin astrologer.''

But, he added, ''Since all the Kremlin astrologers have once again been proved completely wrong, I'm quite happy not to be one.''