ongoing - it is happening now. It is measuring data now, and will continue to do so for a while. variability - that's not completely clear to me. It may be jargon in the field. It may mean 'measuring changes in some parameters'. study - it is research. 'a long way off' - they will not be available for a long time. They need more time to do the measurements.

"ongoing" means that something is still happening as a continuous action. "variability" means that something includes a lot of different results/options. "study", as a noun, means to do research of some kind. --> so "an ongoing variability study" together is referencing research about the levels of change in a subject that has already started and has no completion date as to continue the monitoring of said changes. "a long way off" means that the end/outcome is very far away in time and without any estimation of completion either.