* ASCENSION. 9 p.m. today,

Tuesday and Wednesday, Syfy.

"Mad Men" meets "Battlestar Galactica" in this three-night miniseries starring Brian Van Holt (below) and Tricia Helfer. Set on a spaceship secretly launched in 1963 and now some 50 years into a mission to reach humanity's next home. You may be a couple of hours in before you realize there's something else going on (and that's all I've seen so far). Only you can decide if it's worth turning back or going ahead.

* SAVING MY TOMORROW. 7 and 7:30 tonight, HBO.

Don't want your family to spend generations in space looking for a safe place to land? HBO and the American Museum of Natural History look at climate change from kids' perspectives in this two-part family special that features both celebrities (Upper Darby's Tina Fey narrates a piece on monarch butterflies) and child activists.

* MOM. 8:30 p.m., CBS3.

Another week, another very special episode of a show that's mining comedy out of serious pain. A three-generation therapy session uncovers something Christy (Anna Faris) never told her daughter Violet (Sadie Calvano) about the father the girl never knew.

* THE COLBERT REPORT. 11:30 p.m. Thursday, Comedy Central.

Nation, the final night of Stephen Colbert's Comedy Central show doesn't mean the end of Colbert, who's taking over CBS' "Late Show" from David Letterman sometime next year. But it is a farewell to the "high-status idiot" anchor Colbert's gleefully portrayed for nine seasons. Darned if I won't miss that guy.

- Ellen Gray