When Jeri Ryan joined the cast of ''Star Trek: Voyager'' in its third season, in the fall of 1997, ratings soared 60 percent. They have since remained up, though not at that lofty level, said Rick Berman, an executive producer of the show, UPN's flagship series, shown in New York at 9 on Wednesday nights on WWOR, Channel 9.

Ms. Ryan, a 30-year-old former National Merit Scholar, plays Seven of Nine, a young woman who was assimilated by an alien species, leaving her human identity reduced to a cipher. Forcibly freed from the species by Capt. Kathryn Janeway, played by Kate Mulgrew, Seven struggles to learn what it means to be human. Her battles with herself are mirrored in attempts to help, or sabotage, the ship that are made all the more powerful by her inhuman, laserlike concentration.

''We've had to beat writers off with a stick,'' Mr. Berman said, referring to proposals for scripts that would feature Seven of Nine.

Ms. Ryan's skintight costume and the body it accentuates have also been subjects of several articles and even Web sites, making her character the second most popular after Captain Janeway, commander of the Voyager throughout its four seasons, said Mr. Berman.