Although the probe would carry no cameras in the classic sense, its onboard instruments would include a low-energy charged particle experiment, a magnetometer, a cosmic ray detector, and an energetic neutral atom detector.

FORBES: Jump-Starting A Mission To Interstellar Space

Light ones are more easily deflected than heavy ones, so the two forms of carbon get separated, and when each atom reaches a detector at its expected arrival spot, it can be counted.

ECONOMIST: Monitor