The post-apocalyptic soap opera “Jericho” (9 p.m., CBS) returns for a second season that almost didn’t happen. When CBS announced its new schedule last May, the network had no room for “Jericho.” But a persistent letter-writing campaign by fans convinced CBS to change its mind. A truncated second season will run on the network, while episodes from season one air Monday nights on Sci Fi.

In some ways, the fate of “Jericho” reflects the direction of televised dramas and comedies. Many simply cost too much to justify the small-to-middling audiences they attract on network. Meanwhile, dramas like “Battlestar Galactica” and comedies like “Monk” can thrive on cable, where the schedule allows them to be repeated several times each week. “Jericho” seems like the perfect example of the kind of series making the transition from network to cable.

Set in a tiny Kansas town that has survived a mysterious nuclear attack on many American cities, “Jericho” stars Skeet Ulrich as the estranged son who returns to his family on the eve of the catastrophe.

Despite its post-9/11 atmosphere of paranoia and conspiracy, “Jericho” has an old-fashioned feel to it. With its border wars between rangers on horseback, it conjures images of a post-nuclear Western.

¢ When astronauts first walked on the moon, they declared, “We come in peace for all mankind.” Four decades later, “Nova” (7 p.m., PBS, check local listings) reveals efforts to use NASA astronauts as spies as well as Soviet efforts to train their cosmonauts in the art of outer-space espionage. Wow, and I thought all that jazz in “You Only Live Twice” was fiction!

Tonight’s other highlights

¢ With the audition process concluded, the chosen few travel to Hollywood on “American Idol” (7 p.m., Fox).

¢ The devil finds Halloween depressing and disrespectful on “Reaper” (7 p.m., CW).

¢ Kevin Federline returns to “One Tree Hill” (8 p.m., CW). Wouldn’t you?

¢ Gems, minerals and mud on “Dirty Jobs” (8 p.m., Discovery).

¢ Alex discusses Paul’s strange encounter on “In Treatment” (8:30 p.m., HBO).

¢ A witness shows signs of being more gifted than reliable on “Law & Order: Special Victims Unit” (9 p.m., NBC).

¢ “Swoosh! Inside Nike” (9 p.m., CNBC) profiles the famous sneaker company.