Seven years after the first passenger ship sailed through the Northwest Passage, the Frontier Spirit, one of the few vessels equipped to operate in Arctic waters, will attempt the feat late this summer.

The Frontier Spirit, with a capacity of 164 passengers, will leave Dutch Harbor in the Aleutian Islands Aug. 18 for a 6,000-mile, west-to-east voyage across the top of the world. It is scheduled to arrive in St. John's, Newfoundland, Sept. 16 after passing through the Bering Strait and calling at the Pribilof Islands and many other islands in the waters between the Pacific and the Atlantic.

At the helm will be Capt. Heinz Aye, who was in charge of two of the three previous Northwest Passage voyages. The Lindblad Explorer of Salen Lindblad Cruising, under Capt. Hasse Nilsson, made the first voyage in 1984. Captain Aye took the World Discoverer through the passage in 1985 and the Society Explorer in 1988, both times for Society Expeditions.

Part of this year's 29-night voyage will be in the Canadian Coast Guard's zero discharge zone, where almost no ship refuse is permitted.

In order to protect the area, which stretches from the Beaufort Sea to Lancaster Sound, garbage must be refrigerated and held until the ship reaches a port, and the vessel must be equipped with an oil separator in the bilge to prevent accidental discharge of petroleum.

Fares range from $17,500 to $26,200 a person in double occupancy. Air fare from New York of about $1,495 is extra. Write Salen Lindblad Cruising, 333 Ludlow St., Stamford, Conn. 06912, or call (203) 967-2900 or (800) 223-5688.