Showtime has long made science fiction a staple of its original programming, from “Stargate SG-1” and its updating of “The Outer Limits” in the past to this season’s new offering “Jeremiah.” Continuing in this vein is the intelligent new series “Odyssey 5,” which premieres at 10 tonight on the premium cable channel.

In the debut episode, Manny Coto, the series creator and executive producer, starts things off with a bang, destroying Earth in the early going. The crew of the shuttle Odyssey witnesses the cataclysm. The spaceship itself is slammed by the shock wave, and the five survivors find themselves running out of oxygen and hope.

The crew members drift off into an eternal sleep, only to wake up after their orbiter is picked up by the ancient being known as the Seeker (played by Sir John Neville). He gives them the opportunity to send their consciousness back five years into the past into their younger bodies, in order to prevent the disaster from happening.

So the quintet, led by mission commander Chuck Taggert (Peter Weller), has a primary mission of finding out what group is behind the Earth’s destruction. But they also have the chance to change things in their lives, for better or worse. Future episodes promise to more thoroughly explore the choices they make.

Weller, who is best-known as the title character in the sci-fi films “Robocop” and “Adventures of Buckaroo Banzai,” is outstanding as Taggart, who’s more comfortable with the dangers of space than he is as a parent, including communicating with his crewmate and son Noel (Christopher Gorman, “Popular”).

“Odyssey 5” is a well-conceived and promising work, one that can capture “Quantum Leap” and “X-Files” fans alike. Following the five through to their mission’s end should be a satisfying journey.

Also premiering on Showtime this weekend is a penetrating look at the federal parole system. Shot in a gritty documentary style, “Street Time,” which debuts at 10 p.m. Sunday, examines parole from the perspectives of both the parolee and the parole officer.

Rob Morrow (“Northern Exposure”) stars as parolee Kevin Hunter, a former drug trafficker who has just spent five years inside. His goal is to reconnect with the wife and son he left behind while avoiding his former lifestyle. He soon finds out that it will be difficult for his wishes to come true.

Scott Cohen (“NYPD Blue,” “Gilmore Girls”) stars as James Liberti, Hunter’s parole officer who has a habit of his own to kick. Liberti keeps trying to rehabilitate his parolees, not just revoke their probations and send them back. This attitude clashes with many of those around him. Of a similar mind is Dee Mulhern (Erika Alexander), a streetwise parole officer who worked hard to escape the circumstances that drive many to crime.

“Street Time,” created by former convict Richard Stratton and veteran TV producer Stephen Kronish, does an admirable job of portraying the pitfalls that both parolees and parole officers face. The problem is that it illustrates a relentlessly grim world, which some viewers are going to have trouble connecting with. Like its subjects, “Street Time” faces uphill odds to succeed.