LOS ANGELES (thefutoncritic.com) -- Sci Fi's flagship series "Stargate SG-1" is set to draw to a close as the network has opted not to renew the series for an 11th season. "SG-1" spin-off "Stargate Atlantis" however will continue, with a fourth season set to launch sometime next year.

The news comes just days after "SG-1" aired its landmark 200th episode this past Friday. "SG-1" wraps its summer run on September 22 with the 10 remaining installments due in March (likely placing the series finale in early May).

"Atlantis" likewise will finish its summer stretch on September 22 with the back half of its third season also targeted for a March start.

As for specifics behind the cancellation, industry insiders point to the show's 30% drop in viewership from last summer. "SG-1's" first four installments this season have averaged a 1.45 household rating, down from its 2.05 average during the same period last year. Lead-out "Atlantis" however has only fared marginally better with a 26% dip (1.5 vs. 2.03).

Both series also have fallen short of the network's recent additions this summer: "Eureka" (2.47 average household rating) and "ECW" (2.37 average household rating).

Still to come in January are newcomers "The Dresden Files" and "Painkiller Jane" while both "Battlestar Galactica" and U.K. import "Doctor Who" return for new seasons later this year.

Official confirmation of these developments is expected to be announced shortly.