Abstract: The National Weather Service (NWS) is developing the Radiosonde Replacement System (RRS) to replace its antiquated Micro-ART system, which has been in operation since the late 1980s. Before the new RRS is fielded, NWS is conducting a series of tests to understand the characteristics of the measurements used by operational and research staff. Some of the techniques to be discussed will be use of the GPS-Integrated Precipitable Water sensor developed by the Forecast Systems Laboratory of NOAA, functional comparisons with reference radiosondes produced by NASA, and the use of the RAOB© program, produced by Environmental Research Services, for analyzing and comparing meteorological parameters. Examples of the types of data acquired during each of these tests will be shown.