This week marks a milestone in the history of America's love affair with the captain and crew of the USS Enterprise. Star Trek: The Next Generation boldly goes one step beyond the original Star Trek series with its 80th episode. (Captain Kirk and his crew filmed only 79 segments.) No one is more surprised at the syndicated series' continued success than Brent Spiner, who plays Lt. Commander Data on the show.

"When I took the role four years ago, it was just another job," says Spiner. "I figured we'd do a pilot and then go home. I really thought the odds were against us because people were initially reluctant to accept a new Star Trek. Now here we are 80 episodes in."

Spiner is also amazed that his character, an android possessing super strength and an incredible memory, has become so popular.

"When I was initially cast as Data, my biggest fear was that he has a very small canvas to paint on," explains Spiner. "I thought I was going to get locked into playing something very restrictive.

"But as it's turned out over the years, I wind up doing something other than Data - or doing Data playing at being something else - at least once or twice a year."

Surprisingly enough, Spiner's fan mail is mostly from women intrigued by Data.

"I get a lot of romantic mail," he says. "They're just curious about my availability or they're telling me about themselves - their problems and how difficult life is for them.

"But the letters are really written to Data," adds Spiner, who is single. He believes women are fascinated with Data because "he's a really accessible personality. He's vulnerable and innocent, and there's a feeling that he's somebody who would be kind."

This is the fourth season for Star Trek: The Next Generation (10 p.m. Saturday, WCPX-Channel 6), and Spiner has two more years to go on his contract. But he can't foresee continuing on longer than that.

"There's a dilemma to playing my character," he says. "Data doesn't age because he's an android, but unfortunately I do - and I think I'm like skating on the edge of the envelope right now in terms of age.

"But it's not just a matter of the physical appearance," continues the fortysomething actor.

"Data is an innocent, and there is a point of diminishing return in seeing an older person playing that sort of innocence," he said. "It's kind of comparable to Harpo Marx. When he was young, he was like an angel from another world . . . full of mischief and fun. But in his later films, it was really difficult to accept that innocence. I think the same could be true of my character."