Robert M. Gates, an intelligence staff man, analyst and manager nominated to be the No. 2 official at the Central Intelligence Agency, will appear today before a Senate confirmation hearing in what administration officials hope will mark the beginning of a new, calmer era for the CIA.

Gates, 42, the agency's deputy director for intelligence, has never had a direct hand in covert operations or clandestine intelligence-gathering by the elite branch of the CIA, the directorate of operations, which manages CIA stations abroad.

But he is the hand-picked candidate of CIA Director William J. Casey, who has been a strong advocate and hands-on manager of covert actions.

Said one senior source, "Nearly everyone in the administration and Congress wants less public confrontation. The political squabbling has cost everyone from the Nicaraguan operation, the mining of the harbors, to the charges about leaks . . . . Gates could be deputy or the director of CIA for life if he helps lower the noise level, gets the CIA and its operations out of the headlines and partisan cross fire."

Numerous sources, some of whom criticized Gates for an ambition they call ill-concealed, said he has maintained rigorous standards for objective intelligence production while also responding to the Reagan administration's activist policy agenda to counter Soviet moves in the Third World and elsewhere.

One former colleague said that Gates "does not see the Soviets as comic-strip evil, but has a well-educated hardness fully in line with Reagan administration thinking." Sources said that Gates supports ongoing covert operations but is more inclined to view the CIA's primary function as intelligence-gathering.

Gates is expected to easily win confirmation by the Senate, though some senators may use the opportunity of a public hearing to air longstanding disputes with Casey.

Some in the intelligence community have criticized the selection of Gates on grounds that he probably would not be able to act as the seasoned voice of skepticism, the role of his predecessor, John N. McMahon, who resigned in February after 34 years. McMahon, who headed the directorate of operations in the late 1970s, frequently and passionately outlined the risks of covert operations.

From the time he joined a CIA career training program in 1966, Gates expressed interest in rising to the top, according to past associates. He once lamented to a friend that with so many senior people in the agency from World War II intelligence activities, quick promotion would be unlikely. Gates told a colleague that he lacked the high-level contacts he would need to succeed inside the agency. But Gates quickly advanced himself by winning key staff positions near the center of national security decision-making beginning in the early 1970s, when he became a CIA intelligence adviser for the strategic arms limitation talks (SALT) delegation. He served Presidents Richard M. Nixon, Gerald R. Ford and Jimmy Carter on the National Security Council staff, returning to CIA headquarters in December 1979.

His experience in the White House convinced Gates that CIA analysts ought to be close to policy makers to know their worries and their goals, colleagues said.

This does not mean that the CIA should tailor its intelligence to fit White House policy, just the opposite, Gates has argued. He has maintained that CIA analysts have to know where the policy makers want to go in order to warn them of obstacles.

In the Reagan administration, Gates has served as an administrative aide to Casey and his first deputy, Adm. Bobby Ray Inman. In 1982, Gates was named deputy director for intelligence and is credited with reorganizing the system by which the CIA produces National Intelligence Estimates on every conceivable subject.

Sources said Gates has frequently told Casey and the Reagan administration things they did not want to hear. In 1983 he opened up the issue of military spending by the Soviet Union and concluded that the Soviets were not spending as much on military hardware as the Defense Department had long contended.

Said one source who is critical of Gates' ambition: "He was going against the current . . . . I have to give him credit . . . . He is able to support the the integrity of the process."

Gates is ascending to the agency's No. 2 post at a time when the CIA prepares for what some sources said will be brutal budget cuts and tough questions about its accountability to Congress and its expanding role in the management of covert paramilitary operations round the world.

David Aaron, who served as deputy national security affairs adviser in the Carter White House, said that Gates made some of his own discoveries about CIA inadequacies while he was on loan from the agency to serve as a special assistant first to Aaron and then to Zbigniew Brzezinski, Carter's national security affairs adviser.

Aaron recalled in an interview that in April 1976, the National Security Council requested from the CIA its current studies on the Islamic fundamentalist movement that was gathering strength in the Arab world. "But the [CIA] analysts weren't answering our mail," Aaron said. Aaron said he sent Gates to CIA headquarters at Langley "and when he came back, he was thunderstruck." The CIA, Gates reported, had no studies on Islamic fundamentalism.

As a result, Aaron said, "we pushed them into a program to get people in the academic world to focus on it."

The later failure of the Carter administration to predict the strength of Islamic fundamentalism during the fall of the shah of Iran had an enormous impact on the intelligence community and, according to sources, on Gates.

One senior official said Gates has been "the toughest taskmaster" CIA analysts "have ever had -- he reads everything." This has led to some grumbling, but if confirmed as No. 2 at the CIA his reading list will be much longer and some officials predict he'll have to leave much unread.