It is now official. There is no frightening ''window of vulnerability'' in America's overall strategic nuclear forces. The American people can feel reassured by the conclusion of a presidential panel that, if the Soviet Union were to launch an attack on US land-based missiles, America's formidable arsenal of submarine and bomber-launched missiles would be sufficient to destroy all Soviet targets and defend the United States from nuclear annihilation. Mutual deterrence, in short, still safeguards the peace.
Most people will be relieved, too, that the President's Commission on Strategic Forces goes on to conclude that the United States does not need a new MX mobile missile system to address the problem of ICBM vulnerability. So much for that ill-conceived scheme. But there is likely to be less enthusiasm for the commission's recommendation to place 100 new MX missiles in existing Minuteman and Titan ICBM silos. If those silos now are vulnerable to a Soviet first strike - and if it is far from certain that the silos can be hardened enough to withstand Soviet missiles in the future - it seems pointless to replace one vulnerable missile with another.
For purposes of a bargaining chip? The commission's reasoning is that deployment of MX missiles would pry concessions from the Russians at the negotiating table. But is such a prod needed? When Moscow has approved SALT II, when it is the United States which has slowed down the strategic arms control process, and when the US is about to deploy an unmatched strategic weapon: the Trident II missile with its silo-busting capability? In short, in today's strategic arms race environment it should be possible to negotiate without building threatening bargaining chips, especially unwork-able ones.
Now to the other elements of the panel's report. The public can welcome the fact that this distinguished group of experts has made a comprehensive review and proposed some new options: namely, developing a smaller, single-warhead mobile missile and recasting the START talks with a view to counting warheads rather than launchers. The ventilation of fresh ideas is useful and will help foster public debate.
Like all new ideas, however, this one needs to be examined carefully. On the face of it, the single-warhead mobile missile seems sensible because it reduces the attractiveness of missiles as targets and decreases the number of warheads as targets. But despite the fact that a consensus seems to be building on behalf of the ''singlet,'' it also raises disturbing questions. For instance, would the missile do what its advocates say it would do: compel the Soviet Union to change its entire system to mobile, single-warhead ICBMs? If it did, how would the United States keep track of the new Soviet missiles? In any mobile system the Soviet Union would likely have the advantage when it comes to verification, because of its geographical expanse and the secretive nature of its society.
There is also the worrisome possibility of blurring the distinction between various nuclear weapons, the distinction which now makes arms control possible.In the not too distant future technology will make possible lighter missiles for a dual purpose; that is, having both theater and intercontinental capabilities. A time could thus come when the USSR (if it adopted a new ICBM system) would be moving several thousand single-warhead missiles around the country literally like tanks, and demanding a certain ''edge'' in numbers because of its concern about China. Would arms controllers be able to cope with this? And what would Americans say when droves of US ''singlets'' began moving up and down federal highways?
This is not even to mention the matter of cost - billions and billions of dollars to develop a new system at a time when the economy is not sturdy and unit costs are rising. Can the US afford such a route? Some experts suggest that , if the goal is greater nuclear stability, the US should go back and reconsider some other - less costly and less destabilizing - options such as building more and smaller missile-carrying submarines.
Such questions call for thorough scrutiny and discussion. The President, lawmakers, and public may heave a sigh of relief that the MX mobile missile has been rejected by a bipartisan panel. But that should not lead them to accept uncritically the panel's recommendations. It is just possible that the basic message of the commission report is that, because of technological advances, the landbased ICBM has reached the end of the road, that other means must be found to maintain nuclear stability, and that this places a premium on the most effective means of all - arms control.