THE PROPOSED WORK ENSURES THE CONTINUITY OF THREE LONG-TERM HIGH-QUALITY WATER VAPOR MEASUREMENT RECORDS IN THE UPPER TROPOSPHERE AND LOWER STRATOSPHERE (UTLS). THE IN SITU SOUNDINGS ARE PERFORMED AT LEAST MONTHLY BY BALLOON-BORNE NOAA FROST POINT HYGROMETERS (FPHS) AT BOULDER COLORADO (40 N) HILO HAWAII (20 N) AND LAUDER NEW ZEALAND (45 S). WITH A LENGTH NOW EXCEEDING 40 YEARS THE NOAA FPH DATA SET OVER BOULDER COLORADO IS THE LONGEST OBSERVATIONAL RECORD FOR UTLS WATER VAPOR IN EXISTENCE. THE FPH DATA RECORDS AT LAUDER (~16 YRS) AND HILO (~10 YRS) ARE SOMEWHAT SHORTER IN LENGTH BUT ARE PROVIDING PERTINENT INFORMATION ABOUT UTLS WATER VAPOR IN THE SOUTHERN MIDDLE LATITUDES AND NORTHERN SUBTROPICS RESPECTIVELY. SUPPORTING FUNDS WILL HELP TO MOVE FORWARD THE EXISTING FPH SOUNDING PROGRAMS THAT HAVE PROVEN BENEFICIAL TO NASA S SPACE-BORNE UTLS WATER VAPOR MEASUREMENTS IN SEVERAL WAYS. FIRST THE BALLOON-BORNE MEASUREMENTS HAVE PROVIDED A STABLE AND CONSISTENT FOUNDATION FOR THE DETECTION (AND POTENTIAL CORRECTION) OF BIASES AND/OR DRIFTS IN SATELLITE INSTRUMENTS LIKE THE AURA MICROWAVE LIMB SOUNDER (MLS) AND THE STRATOSPHERIC AEROSOL AND GAS EXPERIMENT (SAGE-III) CURRENTLY DEPLOYED ON THE INTERNATIONAL SPACE STATION (ISS). SINCE TRENDS IN UPPER ATMOSPHERIC WATER VAPOR ARE TYPICALLY SMALL RELATIVE TO SEASONAL AND INTER-ANNUAL VARIABILITY TREND DETECTION REQUIRES ACCURATE AND STABLE MEASUREMENT RECORDS LIKE THOSE COMPILED FROM FPH SOUNDINGS. SECOND THE INEVITABLE DEMISE OF MLS WILL LIKELY REDUCE BY &GT;95% THE CURRENT SPATIOTEMPORAL DENSITY OF UTLS WATER VAPOR MEASUREMENTS FROM SPACE. THE FPH SOUNDINGS PROPOSED HERE WOULD HELP TO FILL ANY TEMPORAL GAP THAT ARISES. THIRD THE FPH SOUNDINGS AT ALL THREE SITES ARE NOW VITAL TO TWO INTERNATIONAL MEASUREMENT NETWORKS THAT FOCUS ON DETECTING TRENDS IN ATMOSPHERIC COMPOSITION AND ESSENTIAL CLIMATE VARIABLES: THE NETWORK FOR THE DETECTION OF ATMOSPHERIC COMPOSITION CHANGE (NDACC) AND THE GLOBAL CLIMATE OBSERVING SYSTEM (GCOS) REFERENCE UPPER AIR NETWORK (GRUAN). BOTH OF THESE NETWORKS DEPEND ON A STABLE CORE OF SELF-FUNDED SITES WITH SUSTAINABLE MONITORING PROGRAMS HENCE THERE IS A FUNDAMENTAL NEED TO ENSURE THE CONTINUITY OF THE FPH MEASUREMENT RECORDS AT BOULDER HILO AND LAUDER.