I’m now realizing I know hardly anything about GPS. Like it was made in the 50’s or something? Do we keep sending more GPS satellites into space? Or are there just the original handful?
There have been several iterations of satellites and systems.
In February 1978, the first Block I developmental Navstar/GPS satellite launched, with three more Navstar satellites launched by the end of 1978.There were off book non US reverse engineered Navstar recievers cobbled together on benches in the mid 80s being trialed as alternatives to LORAN use.
That's a little earlier than your statement of "late 80s".
It'd be documented in, say, Geoscience Australia metadata notes to air surveys of the era.
Of course that'd be a primary source and not wikipedia, nor a wikipedia secondary reference newspaper article.
If you're just concerned with the first satellite launch, ehhhh, sure. As a useable global system it was much later.
"The GPS project was launched in the United States in 1973 to overcome the limitations of previous navigation systems,[15] combining ideas from several predecessors, including classified engineering design studies from the 1960s. The U.S. Department of Defense developed the system, which originally used 24 satellites, for use by the United States military, and became fully operational in 1993. Civilian use was allowed from the 1980s. "
Here's the current list, marked by launch date and Block: