Washington — In the year since a Soviet interceptor shot down a South Korean airliner, there have been no breakthroughs regarding the cause of an incident that helped drive US-Soviet relations to a low point.
Theories abound, and Moscow and Washington this week traded counter-charges over who was responsible for the loss of 269 lives, including that of a United States congressman. Still, much has happened that could help prevent a recurrence of the tragedy:
* The Federal Aviation Administration is using better radar to track aircraft flying the north Pacific route, which passes near sensitive Soviet airspace. In several weeks, the FAA will install a new system that will double the range of radar coverage along the route that Korean Air Lines Flight 7 was flying.
* The US Defense Department is certain to make its NAVSTAR global positioning system of satellites available to civil aircraft free of charge. When this network of satellites becomes fully operational in 1988, aircraft around the world will be able to pinpoint their positions to within 300 feet for the cost of a relatively cheap ($20,000) receiver. The eighth of 18 GPS satellites will be launched next week.
* Airlines flying international routes have ordered their pilots to be more vigilant when using the inertial navigation system (aboard the South Korean airliner and most jumbo jets), which is susceptible to human error as well as occasional malfunction.
''Everybody has really tried to tighten up, I can tell you,'' said one veteran airline pilot, who believes the episode was ''completely the Korean captain's fault. Everybody is saying, 'Do not make a mistake, period.' ''
* Most important, the Montreal-based International Civil Aviation Organization (ICAO) is amending its charter to explicitly forbid the use of antiaircraft weapons against civil aircraft, to improve interception and communication methods, and to forbid the use of civil aircraft for ''inappropriate'' (that is, intelligence-gathering) purposes. Soviet representatives to the 152-member ICAO have agreed to these amendments to the 1944 Convention on Civil Aviation.
The Korean Air Lines 747 was on a flight from Anchorage, Alaska, to Seoul on Sept. 1, 1983, when it flew off course to the west. This took it over the Kamchatka Peninsula and eventually Sakhalin Island. Soviet ballistic missile tests terminate in this region, and much of the steadily expanding Soviet fleet operates here.
Soviet military officials said the 747 was part of a US intelligence effort, which included a US Air Force RC-135 reconnaissance plane and satellite positioned overhead. A Soviet missile test had been scheduled for that night. Others have speculated that the US space shuttle Challenger, orbiting Earth at that time, was part of this spying effort.
US officials strongly denied the Soviet allegations and contended that if the Soviet Union did not know the airliner was a civilian craft, it certainly should have. It complained of Soviet interference with US Navy efforts to locate the one piece of equipment, the 747's flight recorder, which has never been found.
Several books have since been written arguing both sides of the incident. The Soviet Union this week repeated its charge that the Korean jumbo jet was on a ''spying mission.''
A senior official at a US State Department background briefing called these charges ''totally false'' and emphasized that the US ''does not use civilian airliners for intelligence purposes.''
''No agency of the US government even knew the airliner was off course until after it was shot down,'' the official said. ''Therefore it couldn't have been warned.''
After several months' investigation, the ICAO essentially sided with the US. The international body declared that because of equipment malfunction or crew error, the South Korean flight crew did not know that it was off course.
''Since then, there's been nothing new presented that would change our conclusions,'' said ICAO spokesman Eugene Sochor. ''The black boxes were not recovered and most likely never will be.''
The ICAO's air navigation commission (the organization's technical body) has reviewed international flight procedures dealing with communications between neighboring countries and between aircraft. It is expected to recommend that countries like the Soviet Union and Japan (which tracked Flight 7 during part of its intrusion into Soviet airspace) find better ways to exchange information quickly.
The ICAO also is likely to urge that all aircraft - interceptors as well as airliners - be equipped with radios having common emergency frequencies.
Shortly after the airliner was shot down, the FAA sent controllers to Shemya, an island at the end of the Aleutian chain that houses a US Air Force radar facility. The civilian controllers have been monitoring civil aircraft flights along the routes passing near Soviet airspace.
In October, according to FAA officials, a new facility on St. Paul Island will extend FAA coverage to twice the present range of about 200 miles from Anchorage. ''Still,'' says FAA spokesman Fred Farrar, ''four-fifths of the trip is going to be outside radar.''
For this reason, promoters of the new global positioning system (GPS) are urging the federal government and the airlines to make use of these satellites for civil aircraft.
''The only thing that's required is a GPS receiver and a data link,'' says Loren E. De Groot, director of avionics systems at Rockwell International, builder of NAVSTAR. Mr. De Groot says GPS satellites now on station could help keep aircraft on course along the northern Pacific route, and he predicts that civilian airliners will be making use of them by 1986 or '87. The House and Senate this year voted to remove user fees from GPS funding, which has heightened civilian interest in the system.
As for what motivated the Soviet Union to shoot down KAL Flight 7, US officials say they noted a ''heightening of the classic Soviet concern about being encircled by the outside world ... and the inviolability of Soviet state borders,'' as one put it, even before the airliner incident. When Soviet interceptors failed to locate the airliner after it had overflown the Kamchatka Peninsula, a senior State Department official said, ''this produced a decision to shoot first and seek explanations afterward.''