The authors of the congressional ban on antisatellite weapon tests have sent Defense Secretary Caspar W. Weinberger a letter warning that "Congress would not excuse any attempt by the Department of Defense to circumvent the law."

Reps. Les AuCoin (D-Ore.) and Norman D. Dicks (D-Wash.) wrote Weinberger Friday that there was "no legal way" to go ahead with such a test and that "any attempt to do so would provoke the most severe repercussions."

Their amendment, which was part of the omnibus spending bill signed Dec. 19 by President Reagan, bars a test of the U.S. antisatellite system "against an object in space until the president certifies to Congress that the Soviet Union has conducted" a similar test. In 1983, the Soviets declared a moratorium on testing its antisatellite system.

The AuCoin-Dicks letter was triggered by a report Wednesday in The Washington Post quoting one of Weinberger's top assistants as saying the ban "must be undone" so the program could continue. The report also quoted a Pentagon spokesman as suggesting tests may be made against a point in space rather than a target but adding that there would be no "direct violation" of the law.

Although the congressional action stops testing, it does not halt the overall antisatellite program. Congress increased by $15 million a Pentagon request for $150 million this fiscal year to develop the antisatellite system.

That increase, a congressional aide said, was to show the Soviet Union that the U.S. program would be available for testing if Moscow broke its moratorium.

The system under development would consist of a rocket carried aloft and launched by an F15 fighter. The rocket's warhead guides itself into the path of a target satellite and destroys it on impact.

In their letter, AuCoin and Dicks asked Weinberger to inform them of the Pentagon's plans for the antisatellite system. An Air Force spokesman said last week that the problem-plagued F15 program, which is two years behind schedule, was being restructured even before the test ban was approved. He said a new timetable and cost estimate for the $4.1 billion program was expected next month.

The spending bill also has a special $5 million item for the Air Force "to carry out a research program to develop new and improved verification techniques to monitor compliance with any antisatellite weapon agreement that may be entered into by the United States and the Soviet Union."

The Reagan administration has refused to negotiate with Moscow on antisatellite weapons, arguing that a verifiable agreement is impossible because there are so many ways to shoot down satellites, including using any one of the thousand or more silo-based intercontinental ballistic missiles both sides have deployed.

Rep. Les Aspin (D-Wis.), chairman of the House Armed Services Committee, said that he hoped to bring arms-control supporters in the House together next month to discuss antisatellite weapons. He called the test ban "a temporary device to buy time and get the attention of the Reagan administration."

The long-term goal of arms control, Aspin said, "is to promote stability." In the antisatellite area, he said, that means finding a way to make secure the superpowers' high-altitude satellites that monitor nuclear forces and provide early warning of an attack.