Hoping to gain

Astronomers keep track of the spots appearing and disappearing on the visible disk of the Sun, hoping to gain insight into the processes that drive the solar cycle as well as to link solar activity with terrestrial climatic changes.

I would like to know what is the function of "hoping to gain" in the sentence.
it is true if I think like this: Astronomers keep track of the spots hoping to gain insight into processes....
or is it posibble to think that Astronomers hoping to gain insight into ...

what I should think when I come across examples like this. Is "hoping" a verb with -ing or a noun.
if it is verb+ing I think that Astronomers is hoping to gain insight into .....