Searching through the US copyright catalog I didn't see anything that looked like Jonathan Elias was the composer of the lyrics. While Elias was a classical composer for several film scores and commercials (and copyrighted a work called "PBS Main Theme" in August 1984, I didn't see anything copyrighted by Elias that sounded like it matched this song to me. "Requiem For The Americas" seemed close in some ways, but what I could find of it didn't sound right. It is possible Elias made the music and someone else added words. But a lot of his music I heard was not particularly "Aaron Copland-ish" in my opinion.

I did find, copyrighted 1995 to James C. O'Brien, a song called Early light, though I was unable to find anything more about it. The same James C. O'Brien (b. 1929) has 4 other attributed works from the early-mid '90s.

You could try contacting PBS, because other than this post and one or two other comments on blogs with more or less the same set of comments, I'm drawing a blank.