CABLE'S USA THROWS DOWN SATURDAY COMEDY GAUNTLET.

Byline: Ray Richmond Daily News Television Writer

It has been said that the only people who are at home watching television on Saturday night are senior citizens, small children, the parents of those small children, and people who can't get a date.

Perhaps this reputation is one reason Saturday has historically been the lowest-rated TV night of the week. It's the only evening when video rentals compete strongly with prime-time programming.

So it might seem a tad curious that cable's USA Network has targeted Saturday as the night on which it is launching its first-ever weekly primetime lineup, which begins at 9 tonight.

This is the same USA, mind you, that for years occupied a spot as something of a cable laughingstock. It gives weekly exposure to professional wrestling and has long subsisted on a diet of cheesy women-in-distress flicks, cultivating a decidedly lowbrow identity.

The new Saturday lineup won't necessarily do much to change that. It consists of four comedies - two of them new, two not-so-new, none particularly sophisticated - running between 9 and 11 p.m.

Shows include the fourth season of "Weird Science" (from producer John Landis) at 9 p.m., the new "Campus Cops" (also from Landis) at 9:30, the third season of the warped cartoon "Duckman" starring Jason Alexander at 10 p.m. and the new "Weekly World News" at 10:30.

It is an offbeat quartet, to be sure. But USA Network President Rod Perth is convinced that offbeat is what you need to break through in cable these days - and that Saturday provides a unique opportunity to do it.

"Saturday is a tough night, but if you look at every other night on the schedule, it's even tougher," Perth said. "There is less competition and less viewer loyalty on Saturday, and all we need to attract is a quarter of the people who watch the networks to make it successful."

This is the first stage of a USA Network mission that Perth hopes will make it a player on the network stage.

"We have to convince the entertainment community here on the West Coast that USA is very serious about developing product with the best writers and producers, actors and directors," Perth said. "The bottom line is that we can no longer rely on reruns and off-network shows that the studios supply to us. We have to do it on our own."

Very quietly, USA has committed $140 million to original programming for the 1995-96 season. It has also tried to upgrade its image, producing a movie called "My Antonia" that was as good as any film on TV last year.

But USA's bread-and-butter remains the titillating, the sophomoric and the outrageous because that's what has given the network its unique status in the basic cable community.

USA has, for six years running, pulled down the highest ratings of any cable network in prime time. And it boasts a show called "Silk Stalkings" that recently passed the 100-episode mark - a rarity in the cable world.

But clearly, the new Saturday night schedule is a different sort of gamble, an attempt to establish a viewing habit with weekend audiences with a comedy block that Perth describes as representing "the USA sensibility."

There is "Duckman," a cartoon that this season will feature episodes titled "Sperms of Endearment," "Grand-Ma-Ma's Flatulent Adventure" and "Bonfire of the Panties."

And there is "Weekly World News," a TV version of the trashy, outrageous supermarket tabloid that's hosted by the esteemed Edwin Newman and keeps its tongue planted deeply inside its cheek.

The surprise about "Weekly World News" is the man behind it: Brandon Tartikoff, onetime NBC programming chieftain and chairman and now chairman of New World Entertainment.

And not only is Tartikoff the inspiration for the show, he has been pitching it around from network to network for two years to find a taker.

"I was not willing to take 'no' on this project," Tartikoff said.

If it seems a little weird that Tartikoff would push so hard for a show based on such a dubious premise - including such ersatz stories as an island tribe that worships boxing promoter Don King and a doctor who performed a double hernia operation on himself.

But Tartikoff doesn't see it that way.

"This thing works on a lot of levels," he said. "If you want to take it as real, you probably can. If you want to suspend disbelief, you probably can. And if you just want to watch it as a great hoot, that works, too."

And if you're home watching TV on Saturday night, well, you just sort of have to take your chances.