The Senate Select Intelligence Committee, worried that the U.S. ability to keep a spy satellite watch over the Soviet Union may be slipping away, has formed a prestigious panel of outside experts to assess government policy in this area.

Though the panel was formed, and held its first meeting, more than a year ago, its existence has never been made public, Senate sources acknowledge.

Its formation, reliable sources report, reflects a variety of concerns within the committee. These range from fear that electronic eyes of U.S. satellites could be blinded by the Soviets in a crisis without any U.S. backup capability, to a feeling that reorganization of the nation's intelligence apparatus two years ago may have stifled inventiveness in an important field and one in which the United States has always led.

The move by the committee to set up a panel of experts, sources say, also reflects in part of vacuum in independent assessments on such issues that has existed since President Carter abolished the longstanding Presidential Foreign Intelligence Agency Board as part of the intelligence reorganization.

The disbanding of the group of leading civilian authorities -- who were supposed to keep watch on the Central Intelligence Agency -- was sharply criticized by some at the time. And now, specialist say, there is nothing to replace it.

Included in the new committee panel, sources report are William O. Baker, recently retired president of Bell Laboratories, who was a member of the advisory board; the former top Air Force civilian official directing reconnaissance satellite programs, Alexander flax, now head of the Institute of Defense Analysis; two former CIA deputies, Carl Duckett and Donald Steininger; Frank Lindsey, chairman of the board of Itek Corp.; Dr. Sidney Drell, deputy director of Stanford University's linear accelerator, and Robert Garwin of IBM.

The letter asking them to participate was signed by Intelligence Committee Chairman Birch Bayh (D-Ind.) and Vice Chairman Barry Goldwater (R-Ariz.) as an expression of bipartisan concern, sources say.

Bayh, in particular, congressional aides say, is reported to be interested in building a greater backup capability in strategic reconnaissance.

For example, other sources say that when the 1973 Middle East war broke out, the Soviets had one intelligence-gathering satellite in orbit able to watch and photograph some of what was going on below. Within two weeks, there were six such Soviet satellites in orbit. The Soviets' ability to put so many additional satellites in space so quickly stunned U.S. observers.

Panelists are studying whether the United States also should have some standby capability to restore space-borne intelligence-gathering quickly if the Soviets, with antisatellite weapons, were able to blind viewing devices of U.S. craft watching such things as missile or troop movements.

At the moment, they say, there is no quick way to do this, and they are looking into how vulnerable the U.S. satellites may be to attack and ways to overcome it.

One way might be to send satellites into orbit for only a short time so that Soviet ground stations cannot track them long enough to get an accurate shot.

There also is study of how best to use the National Aeronautics and Space Administration's space shuttle for intelligence purposes, if necessary. s

Furthermore, there reportedly is concern about U.S. battlefield commanders in Europe, who now get much of their intelligence information via satellite, and what would happen if this were suddenly stopped. This also has put new emphasis on aircraft and unmanned camera-carrying drones. But space, sources say, is the main focus of concern.

Existing U.S. satellites, which are vital for giving the president accurater information so that he doesn't fire retaliatory missiles too late or too early, are highly sophiscated and widely estimated to be better than their Soviet counterparts.

But the feeling on the committee, sources say, is that the administration is no longer taking new initiatives in the intelligence field and that the committee may want to challenge this if there are legitimate grounds.

Sources say that, as good as U.S. satellites are, there has not been much new in recent years, and nothing major in sight comparable to the innovativeness of the past. There was intense activity in the U.s. space program for 15 years between the latter 1950s and the early 1970s. It may be that there are no more bright ideas, but it seems too dangerous to accept that, one source said.

The committee is said to be concerned that one reason for this situation is that the system is throttling new ideas.

In this view, the federal intelligence reorganization two years ago that centralized budgeting authority for a variety of satellite programs within the CIA has caused a bureaucracy to form over it.

A Defence Department official who works in satellite systems corroborates this judgment, saying that red tape and bureaucracy is now so rampant that it is almost impossible for managers to be technically creative.