The Supreme Court opens its 1985 term today confronting a recharged, revamped and newly aggressive Justice Department effort to translate the Reagan administration's views on race, religion and abortion into the law of the land.

The administration will go full tilt against civil rights organizations over the issues of affirmative action, voting rights and racial discrimination in the criminal justice process.

It will seek, for the first time, an outright reversal of the 1973 decision legalizing abortion and new federal power over medical treatment of severely handicapped newborns. And, as part of its continuing effort to bridge the gap between church and state, it will ask the court to allow student prayer groups to meet in public high schools.

The tone and substance of the administration's arguments before the court are expected to be different this year. Gone are attorney general William French Smith and solicitor general Rex E. Lee, low-key conservatives who were criticized by some on the right for their restraint in approaching the court.

The Justice Department is now firmly in the control of more activist conservatives, led by Attorney General Edwin Meese III, who has recently criticized the court publicly for some of its most famous decisions on civil liberties.

In Solicitor General-Designate Charles Fried, on leave from Harvard Law School, Meese has a Supreme Court litigator who is seen as far more amenable to the administration's ideological banner.

Fried's brief urging reversal of the 12-year-old abortion decision is seen as the first and clearest evidence of the change.

The administration's chances for success are unpredictable. The splintered court, with its many 5-to-4 rulings, has followed a zigzag course in dealing with some of these issues, giving a little one year only to take a little back the next. Conservatives within the administration and outside, whose high hopes after the 1983 term were dashed last year, are only cautiously optimistic. They do not expect a string of major victories.

Liberals, who no longer expect big gains at the court, say that they will be satisfied to avoid significant losses.

The court is the second oldest in history, with five justices older than 76. Justice William J. Brennan Jr. will be 80 in April. Chief Justice Warren E. Burger and Justice Lewis F. Powell Jr. both turned 78 last month. Thurgood Marshall is 77, and Harry A. Blackmun will be 77 next month.

If there are no changes by this time next year, the court will be the oldest in history, older than the famous "nine old men" who were the bane of Franklin D. Roosevelt's New Deal.

Several of the justices have been ailing in recent years, but none seems inclined to step down soon unless forced to by ill health.

Brennan looks and sounds more robust than he has in years; Marshall insists, "I'm going to serve out my term, and my term is for life." Powell, the critical swing vote in most major cases, says he will not leave as long as his doctors say he can do his work. Powell was hospitalized last year for removal of a cancerous prostate, but he has been selecting his clerks for next term.

Blackmun complains publicly of being tired but continues to travel the country making speeches, often commenting on the health of his colleagues.

Powell, along with Blackmun and Byron R. White, 68, are expected once more to be swing votes, holding the key to the court's direction.

The court is also among the most stable in history. Powell and William H. Rehnquist joined the court 13 years ago, and only two justices, John Paul Stevens and Sandra Day O'Connor, have been there less than 13 years.

Stevens, 63, has been there 10 years, while O'Connor, at 55 the youngest justice, is starting her fourth term.

The critical showdown between the Reagan administration and the civil rights movement could come in an affirmative action case from Jackson, Mich., and in one of several similar cases from Cleveland, New York City and Florida.

The court has already agreed to hear the Michigan case, Wygant v. Jackson Board of Education, which tests the constitutionality of a voluntary agreement between a school board and a teachers' union to lay off more senior white teachers than minority teachers to achieve racial balance. A group of white Jackson teachers said the agreement was unconstitutional "reverse" discrimination.

Two years ago, in a case involving firefighters in Memphis, the court ruled that judges may not override bona fide seniority systems to protect recent hiring gains by blacks under affirmative action programs.

The administration insists that, after the Memphis ruling, preferential hiring and promotion can only be given to individuals who can show they had been discriminated against.

If that is true, almost all broad affirmative action plans would be illegal, since they give preference to whole classes of minorities without requiring a showing of individual discrimination.

Every appeals court that has considered the administration's interpretation of the Memphis ruling has rejected it. In this year's Michigan case, the justices could settle the question.

The power of black voters is at stake in a voting rights case from North Carolina, Thornburg v. Gingles. This is the first high court review of 1982 amendments to the Voting Rights Act barring any redistricting measures that dilute minority voting strength, whether intentionally or not.

This case became especially high-profile when the administration enthusiastically sided with North Carolina, arguing that recent black electoral successes there prove that there was no discrimination. The administration's position led to an unusual counter-brief filed by Senate Majority Leader Robert J. Dole (R-Kan.), the key sponsor of the amendment.

The court will also examine alleged racism in the criminal justice process. In a case from Franklin, Va., Turner v. Sielaff, the court is being asked to decide whether lawyers representing a black man accused of killing a white man during a robbery have the right to question potential jurors about their views on race.

In another criminal case, Batson v. Kentucky, the court will decide whether prosecutors can employ peremptory challenges -- removal without cause -- to exclude blacks from sitting on a jury. The court will reconsider a 20-year-old ruling allowing this practice.

The court may decide to consider whether statistics showing that killers of whites are sentenced to death far more often than killers of blacks render Georgia's death penalty statute discriminatory.

Capital punishment opponents say the Georgia case may be the last broad legal challenge to the death penalty for the foreseeable future. While there will be appeals in individual cases and against specific state procedures, experts say the Georgia case, McClesky v. Kemp, offers the broadest challenge to the penalty itself.

The court's decision last spring to hear two abortion cases set off alarms on both sides of the issue. The cases, Diamond v. Charles and Thornburgh v. American College of Obstetricians, involve efforts by Illinois and Pennsylvania to regulate abortion.

The laws place various obstacles in the path of women seeking abortions but do not ban them or explicitly challenge the right to an abortion.

The administration, in an unusual move, stepped in and raised the ante by filing a brief urging the court to go beyond the issues in the cases and overrule the 1973 decision legalizing abortion, Roe v. Wade. Most observers say a reversal is extremely unlikely.

The court may end up dismissing both of these cases.

Sources said several of the justices who agreed to hear the Illinois case thought incorrectly that the state was appealing the case, which it is not. That leaves as the only challenger of the lower court ruling an Illinois doctor who may not be legally entitled to pursue the appeal.

As for the Pennsylvania abortion case, the justices are not sure they have jurisdiction to hear it and have deferred that crucial question until after the oral argument Nov. 5.

Another sensitive case involves federal power to control hospital treatment of infants born with severe defects.

The administration two years ago said a 1973 law intended to protect handicapped persons empowered it to intervene in "Baby Doe" cases and override a decision by parents and doctors to withhold treatment.

A federal appeals court rejected the administration's view in Heckler v. American Hospital Association.

One of the most important cases of the term could be an Indiana controversy involving gerrymandering -- drawing political boundaries that favor one party. If, as most observers predict, the high court overturns the lower court in Davis v. Bandemer, the case will have little practical significance. But if the justices say that time-honored gerrymandering is unconstitutional, the impact would be extraordinary, thrusting the judiciary into political battles everywhere.

In 1981 the court ruled that public colleges must grant student religious groups the same access to school buildings that they give to nonreligious organizations.

This term the court will decide (Bender v. Williamsport School District) whether high schools may bar teacher-supervised prayer meetings during periods set aside for extracurricular activities.

The court has traditionally enforced church-state separation more strictly in elementary and secondary schools than in colleges, on the theory that younger children are more susceptible to being pressured or influenced by religious exercises.

Congress passed a law in July requiring school systems to give religious student groups the same right to hold meetings as other groups.

The law itself is technically not at stake in the case, but the court's ruling is likely to determine the law's constitutionality.

Three other cases raise important issues of accommodating religious beliefs and government needs.

In Witters v. Washington, the court will decide whether states must deny educational aid to the blind when that money will be used to train a blind student to become a minister.

Another case, Goldman v. Weinberger, asks whether the military can prohibit an Orthodox Jewish rabbi from wearing a religious skullcap while working as a psychologist in a military hospital.

Also on the docket this term are several important criminal cases and First Amendment controversies over obscenity and libel law.