Egypt is so far behind Israel militarily today that the Sadat mission could be put under the heading of desperation diplomacy, according to some hard-eyed administration assessments.

Egyptian President Anwar Sadat is at least a year from regaining the military strength his forces had in October, 1973, when they launched an attack across the Suez Canal and into the Sinai Desert, according to administration estimates.

And even if Sadat was given a year for improving his forces while the Israeli war machine remained as it is today, these officials added. Sadat still would be much weaker relatively than he was four years ago.

Since the 1973 Yom Kippur War, the Israelis have jumped far ahead of Egypt not only in quantity of weapons but also in quality. Egypt, even with unlimited money for arms, is at least five years away from getting the sophisticated technology that already is part of Israeli forces, according to these estimates.

The Israeli technological edge includes laser aiming devices which enable to tank to destroy the enemy in the first shot, a wide variety of electronic jamming equipment to block communications and foil antiaircraft missiles, and advanced vision devices so gunners and tankers can fight at night.

Also, thanks to American military aid running at the rate of about $2 billion a year, Israel has bought an air force far better equipped than ever before for deep penetration raids into Egypt.This long-range penetration force, which threatens Egyptian ports and industries, consists of U.S. F-4 fighter bombers, long-range F-15 fighters and tankers to refuel them in flight.

In contrast, U.S. analysts asserts, Sadat's ground and air forces are plagued with shortages of spare parts, his antiaircraft defense has big holes in it, and advanced electronic warfare equipment to go with the weapons Sadat already has is not available unless he turns back to the Soviet Union.

Egypt, unlike Israel, has no modern industrial base for turning out sophisticated weapons. The French are discussing with the Egyptians the possibility of setting up a Mirage fighter plant in Egypt, but it would be years before such a plant could go into production if the negotiations succeed. The Carter administration would oppose such a plant in Egypt, officials indicated, because it would amount to further proliferation of weapons.

All this does not mean, analysts stress, that Egypt today is at the complete mercy of Israel. They said Egypt has enough tanks, antitank weapons and trained soldiers to put up a credible defense against an Israeli offensive. But a dug-in defense is a lot different than a highly mobile offense which can launch a sudden strike to force negotiations.

Pentagon officials who have been briefed on Egypt's plan for the Yom Kippur War of 1973 say the idea from the outset was for the Egyptians to make a limited thrust into the Sinai to gain diplomatic leverage. One reason this offensive strike failed, both U.S. and Egyptian military leaders assert, is that the attacking Egyptians met such little resistance that they went beyong their protective air umbrella and left gaps in their armies in the process.

From strictly a military standpoint, specialists agree that Sadat's mission cannot help but pay off. If nothing else, they assert, he has bought Egypt time by cooling passions on both sides.

Also, it is pointed out, both Egyptian President Sadat and Israeli Prime Minister Menahem Begin have, through their spectacular, televised diplomacy, built constituencies around the world that will pull them to the Geneva peace talks whether hawks in their cabinets like it or not.

The only military negative cited by the specialists is the possibility that Syria, feeling isolated by Sadat's diplomacy, may do something radical on its own. But these officials stress that this is just something to watch, with no evidence yet that Syria is going that route.