Energy ranges, knowing exactly how far you are from the source of the neutrinos, and background exclusion. If you are too far from the source, the mixing you m

Energy ranges, knowing exactly how far you are from the source of the neutrinos, and background exclusion. If you are too far from the source, the mixing you might be measuring might have happened already happened. You can build a detector right next to the source, and also far away, and correlate the differences. External interference can be excluded on energy range, direction, and “timing” - you know exactly when the pulse happened in the source and can exclude things outside that window (as the neutrinos all travel at the speed of light to within measurement error). Things like neutrinos from the sun can and have been measured, but for many things you want to measure you need more careful control.