Complex sentence: It should also be noted that the average radiosonde is lost and never recovered; however, for the more expensive instrument packages, balloon-borne unmanned gliders (or UAVs) are used to ensure recovery.
Split into simpler sentences: It should also be noted that the average radiosonde is lost and never recovered. For the more expensive instrument packages, balloon-borne unmanned gliders (or UAVs) are used to ensure recovery.