European Space Agency (ESA) has 3 satellites that work in a coordinated fashion to measure Earth’s changing magnetic field. Here’s the description from ESA
“Swarm, a constellation of three satellites, studies Earth’s magnetic field. Swarm aims to offer a unique view inside Earth: to study core dynamics, geodynamo processes and core–mantle interaction; magnetism of the lithosphere and its geological context; 3D electrical conductivity of the mantle related to composition; and magnetic signature related to ocean circulation. In addition, Swarm data will be used to study the Sun’s influence on the terrestrial system by analysing electric currents in the magnetosphere and ionosphere. It will also play a role in improving our understanding of the impact of the solar wind on the dynamics of the upper atmosphere. Each satellite carries a vector and absolute scalar magnetometer, an electric field instrument, an accelerometer, a GPS receiver, star trackers and laser retroreflectors. The Swarm satellites were launched on 22 November 2013 on a Rockot launcher from Plesetsk, Russia. Mission control is carried out at ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany and science data are distributed through ESA’s centre for Earth observation (ESRIN) in Frascati, Italy.”
There is a single web page that has all the information you neeed
The “mission status” part of this web page is especially important. The technical language of the web page should not discourage you. There is a wealth of information there.
The scientific journal “Geophysical Research Letters” has a special issue dedicated to the most recent SWARM results:
For the earlier more sensational results from the SWARM you can check out my blog post