US Defense Department will stop providing satellite weather data

Is that possible? I thought GPS works by just listening for signals from GPS satellites?

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?

The GPS signal can be encrypted such that only the army can access it. The not encrypted signal can be made less accurate or disabled over specific regions.

The basics of it are it's a digital synchronized time signal sent out by a constellation of satellites. Devices listen for at least 3 separate streams of time signals and the. triangulation happens to get a position.

Irrc the satellite signals not encrypted or whatever were randomized to be inaccurate on purpose. This is mitigated these days by using stuff like cell towers - we know exactly where they are. they pick the same signals out and send out corrections to the randomized data which increases accuracy.

Late 80s, early 90s for civilian use.

There have been several iterations of satellites and systems.

Late 70s:

  In February 1978, the first Block I developmental Navstar/GPS satellite launched, with three more Navstar satellites launched by the end of 1978.

We're coming at this from different angles.

Probably easiest for the OP just read the Wikipedia article.

Not sure about yourself, I'm coming at it from the angle of the dates the local (Nor'West Australia) ham operators started picking GPS signals from navigation satellites .. that and recording transmissions from the Harold Holt submarine communications base passed the time.

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.

Early Block I was mostly used for testing.

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:

https://en.wikipedia.org/wiki/List_of_GPS_satellites