"CBS Reports: A Time to Die" adds another ray of illumination to a dark subject and another valuable hour to television's accumulated literature on death and dying. Correspondent Marlene Sanders visits with members of Omega, a Cambridge, Mass., self-help group that helps sustain those who are terminally ill and those who live with and survive them. It isn't as depressing as it sounds, and even if it were, it would be a rewarding and admirable report.

This documentary, at 10 tonight on Channel 9, is the kind of thing the tiny army of loonies ever on the attack against "Network News" always completely ignores; it is on the virtually unassailable side. The program focuses on several of those involved with the group, but it keeps coming back to Jack Trahant, a 38-year-old Cambridge teacher who, during the filming, was suffering from bone cancer, lung cancer and inoperable brain cancer. "I think the brain cancer is what's going to do me in," he says matter-of-factly during a drive with Sanders.

Trahant doesn't spill over with inspirational pieties, but the more he talks, the more one admires him. He has a compelling softspoken manner and seems privileged to the kind of internal reconciliations sometimes evidenced by the terminally ill. "I guess I am kind of resentful, 'cause I have a 3-year-old, and I'll never see him grow up," he tells Sanders. "He won't even remember me. I'm almost certain."

Jack Trahant died after the completion of the documentary. What he left behind on film will be very important to many of the people who see it.

Other cancer victims are interviewed, as are those going through the pain of what is rather floridly called "bereavement." One man who lost his wife to cancer says, "Unfortunately, I never learned how to cry." A widow says that when deep in grief, "You do find out who your friends are."

Sanders is awfully rigid in her interviews and narration, but this is preferable to the obvious pitfall of such an assignment--patronizing or sentimentalizing these people who have allowed cameras into moments of the greatest intimacy. Film editor Ira Klein's deft touch and the cinematography of Greg Andracke have a lot to do with the striking impressions made by this report, which was produced and co-written (with Sanders) by Kent Garrett. It strives to be more thought-provoking than heart-wrenching but is in fact both.