Helsinki meeting seen as prelude to November summit. US and Soviet foreign ministers plan to meet for talks tomorrow

``We at least want to explore, to find out what the possibilities are.'' That's how a senior Western diplomat here describes the run-up to November's superpower summit in Geneva.

An important benchmark of how that exploration process is going is the meeting here this week between United States Secretary of State George Shultz and Soviet Foreign Minister Eduard Shevardnadze.

Both countries are hopeful that the meeting -- the first encounter between the two since Mr. Shevardnadze took office -- will provide a road map for the time remaining before November.

The makeup for the delegations suggests that both would like to see progress in the key area of disagreement between the two countries -- arms control.

Both Shultz and Shevardnadze have brought key arms control advisers along: Paul Nitze and Max Kampelman for the US, and Yuli Kvitsinsky for the Soviet Union. Mr. Kvitsinsky and Mr. Kampelman are negotiators at the current arms control talks at Geneva. Mr. Nitze, formerly a top negotiator, is a White House adviser on arms control and disarmament.

In Moscow, Soviet Leader Mikhail Gorbachev announced Monday that the Soviet Union will impose a unilateral ban on nuclear test explosions beginning Aug. 6. That is the 40th anniversary of the explosion of an atomic bomb over Hiroshima. The Soviet ban will expire Jan. 1, Mr. Gorbachev said.

US diplomats had expected such a move. The moratorium appears to be designed to put additional pressure on President Reagan to be conciliatory at Geneva.

Gorbachev's announcement closely followed an invitation from Washington for the Soviet Union to send observers to Nevada to monitor a US nuclear-weapons test.

Both Shultz and Shevardnadze are here to observe the 10th anniversary of the signing of the Helsinki agreement on security and cooperation in Europe. However, their minds are much more likely to be on the future course of superpower relations. The Soviets have clearly gone on the offensive, hoping to depict the US as the chief impediment to continuing peace in Europe.

The Soviet delegation has scheduled a press briefing every day of the conference. Tass, the official Soviet news agency, continues to lambast the US for allegedly interfering in the internal affairs of other countries under the ``pretext'' of concern for human rights.

Shevardnadze took a less strident tone in his initial statement upon arrival at Helsinki's international airport, however. The most important thing he would be doing in Helsinki, he said, was to ``defend peace.''

The Soviets are doubtless prepared to hear strong criticism of their human-rights record. US officials indicate that Shultz will give a tough appraisal of Soviet human-rights practices during his speech, which is scheduled for Wednesday.

Shevardnadze is scheduled to speak before Shultz, with neutral Austria wedged in the middle.

Both men will be involved in a marathon round of meetings with other foreign ministers during the three-day gathering. It is from these meetings that many diplomats will form their initial impressions of the new Soviet foreign minister.

But perhaps some of the most telling -- albeit unintentional -- commentary on conditions inside the Soviet Union has come from the Soviets themselves, specifically the host of Soviet journalists and government officials here for the Helsinki meeting.

For most of them a trip outside the East bloc is extraordinary. And Helsinki, with its stylish shops and bewildering array of goods, clearly overwhelms them.

One shop clerk said that watching these Soviets shop is a startling and saddening experience.

Many, he says, repeatedly buy a single small item -- such as a ball-point pen -- in order to collect as many plastic shopping bags as possible.

Such bags are extremely scarce in the Soviet Union, and any with foreign printing on them are considered a prestige item.

It was clear, said another clerk, that these were people from a deprived society.

``I think it is wrong,'' he said, ``to keep an entire country prisoner like that.''

That is a sentiment with which many critics of the Soviet Union would surely agree.