Unobtanium in the 21st century
I was watching this old PBS NOVA program (the lip synch is off) about the Earth's magnetic field.
source: https://www.youtube.com/watch?v=NJUTUFAWfEY
At about 10 minutes into the show there is a brief sequence with Mario Acuna at NASA Goddard mentioning how magnetic fields are measured. At about 13 minutes he shows what appears to be a fluxgate magnetometer which is a toroid wound with an excitation coil with another sense coil wound over the toroid.
Doing a little searching I found this page:
https://science.nasa.gov/technology/technology-highlights/rediscovering-the-lost-art-of-fluxgate-magnetometer-cores
Also this page:
https://gi.copernicus.org/articles/8/227/2019/
It sounds like the quantities in question are so small that no one can justify having the people on hand to keep making these cores. I wonder how many other projects there are like this ?
I wish I knew more about this stuff.
Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm