microgravitational equipment ...???
If this equipment can detect the gravitational difference between an empty cavity and the same underground area filled with dirt then it is indeed sensitive and awesome!
I’d like to get a good look at equipment such as this.
Less sensitive gravity meters have been around for a long time - I think from the 1800’s? Gravity meters in the 40’s and 50’s were important in exploring the large basins for oil. Sedimentary rocks (where the oil is) are much less dense than the metamorphic and igneous rocks.
Microgravity has been around for quite awhile - the 80’s or so? And they are VERY sensitive, so wind blowing will cause errors. Even an ocean storm with waves crashing on the shoreline 100’s of miles away can affect the data. (Probably the limiting “weather” conditions mentioned in the paper).
BTW - I always get a kick out of the media’s term of “ground breaking” when discussing 20+ year old technology as so often happens when they discuss these types of things.