[tj_astro]

The instrument is the particular radar. They usually have two at each location. Each radar is essentially a linear phased array that creates multiple possible beam locations in the radar plane. They light up a beam as a satellite passes through in order to collect measurements. TLDR an instrument has multiple beams.

[dguest]

Ok so there should be "beams" coming from each "instrument"? I didn't see that, but some of the sites are inactive at the moment.