Tribunal resumes work while awaiting crucial ninth member. SUPREME COURT'S NEW YEAR

The United States Supreme Court goes back to work today with an opportunity to guide the social direction of the nation for decades to come. In cases coming up immediately the justices will wrestle with the issues of capital punishment, union power, protections for criminal defendants, and homosexual rights. Deep ideological division on the court was seen late last year with 4-to-4 votes on school prayer and abortion. This left in place appellate court decisions that struck down a New Jersey law allowing a moment of silence in public schools for individual meditation and partly invalidated an Illinois statute restricting minors' access to abortion.

The absence of a ninth, and deciding vote, was due to the retirement last summer of Associate Justice Lewis Powell Jr. It is expected, however, that Judge Anthony Kennedy, President Reagan's choice to fill the vacancy, will be confirmed by the Senate in time for him to take his seat for the February-March sessions.

The issues of school prayer, abortion, capital punishment, and public aid to parochial schools have been high on the agenda of the Reagan administration. But so far the high court has rejected school prayer and parochial aid as violative of First Amendment separation of church and state, allowed abortion on the basis of privacy rights, and upheld the death penalty, but with restrictions as to fairness.

Although these highly controversial questions will come to the court again in other cases, judicial scholars do not foresee a sharp new direction - even with the addition of Judge Kennedy.

Conservatives had hoped that Kennedy, if confirmed, would tip the balance in favor of school prayer and toward restrictions on abortion. The nominee, however, has indicated to the Senate Judiciary Committee that he has no social agenda and that he would not predetermine broad issues but would decide individual cases on their constitutional merits. University of Virginia political scientist David O'Brien, one of the nation's most respected court watchers, predicts ``fine-tuning [of previous decisions] but no clear change.''

Professor O'Brien terms Kennedy ``as close to Powell as you can get.'' The latter was considered the court's ``pivot,'' with his vote often tipping the scales in highly controversial cases. Powell tended to be conservative in business and criminal-justice matters but moderate to liberal on individual rights.

Many judicial scholars saw last fall's bitter fight over the nomination of Judge Robert Bork to the high court, and the Senate's rejection of the nominee, as a watershed for judicial direction in the US. Both liberal and conservative analysts saw Judge Bork's ideology reinforcing the concept of ``original intent'' and challenging recent interpretations of privacy and equal protection as potentially having a major impact on the nation's judicial direction.

On the liberal side, Harvard Prof. Lawrence Tribe strongly opposed Bork as far out of the legal mainstream. But conservative Bruce Fein of the Heritage Foundation applauded Bork's approach as one that would bring the Supreme Court back into balance, adjusting many liberal rulings of the 1950s and '60s.

Professor Tribe sees Judge Kennedy as a mainstream conservative. And Fein is not as optimistic about the prospect of abrupt changes in the court's direction as he was during the early years of the Reagan administration.

President Reagan has made three appointments to the Supreme Court - Sandra Day O'Connor, Antonin Scalia, and now Kennedy. Professor O'Brien says that Mr. Reagan will likely get no further opportunities to change the high tribunal. Even if a vacancy were to occur, he explains, a Democratically controlled Senate would probably block a new court nomination until after the November presidential election.

The court today will first hear a dispute to determine whether unions may, over the objection of dissenting workers, use members' dues to finance support of political candidates and causes (Communications Workers of America v. Beck). The outcome of this case could significantly shape the outside political activities of unions.