Like anevolvedmonkey said, I had never even heard of this experiment. When I clicked on the link I thought that you would be talking about the frame dragging experiment Gravity Probe B.
Thanks for the new thing to read up on.
I was thinking of writing an article on the anti-matter factory at Cern and the test where they let anti-hydrogen fall a short distance and measure the acceleration to see if it is the same as for hydrogen (i.e. the GBAR experiment).
The gravity probe B satellite was not targeting the equivalence principle itself (that is the main topic of this post), and has thus another scope. I am glad that you learned something here :)
Concerning gbar, do you mean this? :D
Yes. You beat me to it. :)
Well, repetition is not necessarily bad :)