Mr. Reagan in Moscow

SO Mr. Reagan is going to Moscow after all. Good. Whether he and Mr. Gorbachev will have made enough progress on strategic nuclear arms reduction talks to initial a treaty at the May 29-June 2 summit remains to be seen. In any event, his going to Moscow helps to round out a presidency that began by being preoccupied with domestic economic issues and phobic about an imagined universal Soviet ideological and strategic threat. Reagan and Gorbachev have fallbacks if the START treaty cannot be put together in time. Time remains for yet another summit, their fifth. If it were to occur in the fall, so much better for the Republicans - who, you might remember, warned eight years ago of a similar ``October surprise'' by Jimmy Carter. For the spring summit, the principals could still focus on nuclear testing: Progress has been made on both the Nuclear Threshold Test-Ban Treaty and the Peaceful Nuclear Explosions Treaty. The Afghanistan endgame has yet to be played out, and the two leaders could make something of a deal on Soviet aid to the Kabul regime and United States support for the Afghan guerrillas. Then there are the domestic political benefits of a summit: Gorbachev might appreciate some image-shining in advance of an important Communist Party conference later in June, while Reagan would like to counter recent legislative failures.

But frankly, these are minor considerations when set against the stronger imperatives of establishing a framework for arms reductions and US-Soviet dialogue.

The START obstacles are not minor. As David Boren, chairman of the Senate Intelligence Committee, warned this past week, the US is not yet ready to verify compliance with an arms pact that would allow Soviet mobile land-based missiles and small sea-launched cruise missiles. Washington wants limits on the mobile land-based missiles; Moscow wants to curb space-based defenses.

Whatever the difficulties, Reagan's Moscow trip is the first for an American President since President Ford met with Leonid Brezhnev in 1974. For many reasons, Reagan now reflects the basic healthy American abivalence about the Soviets: wary but confident enough in US strength to talk about peace.