THE UNIVERSITY OF HOUSTON (UH) AND ST. EDWARD S UNIVERSITY (SEU) HAVE BEEN WORKING COLLABORATIVELY SINCE 2016 TO DEVELOP A MORE CAPABLE BALLOON BASED SONDE TO MEASURE SO2 IN THE ATMOSPHERE. THE RESULT OF THIS COLLABORATION IS A NEW SONDE WITH IMPROVED UPPER AND LOWER DETECTION LIMITS COMPARED TO PREVIOUS DUAL-OZONESONDE METHODS AND THE ABILITY TO MEASURE SO2 AT CONCENTRATIONS GREATER THAN O3 A LIMITATION OF THE PREVIOUS METHOD. INITIAL FIELD TESTS AT KILAUEA IN FEBRUARY 2018 SHOWED SIGNIFICANT VARIABILITY IN THE SENSITIVITY OF THE SONDE IN THE AMBIENT ATMOSPHERE BOTH FROM ONE SONDE TO THE NEXT AND BETWEEN ZERO-AIR CALIBRATION AND AMBIENT SENSITIVITIES. IT WAS HYPOTHESIZED THAT DIFFERENCES IN RELATIVE HUMIDITY (RH) WERE AFFECTING THE SO2 TRANSMISSION EFFICIENCY (TE) OF THE O3 DESTRUCTION FILTER WAS THE CAUSE OF THE OBSERVED VARIATION IN SENSITIVITY. SUBSEQUENT LAB TESTS HAVE SHOWN THAT SO2 TE IS REDUCED AS RH INCREASES BUY AS MUCH AS 50% AT HIGH RH. THE ADDITION OF A NAFION MOISTURE EXCHANGER ENCASED IN SILICA GEL DESICCANT DRIES THE AMBIENT SAMPLE TO LOW RH LEVELS SUCH THAT THE FILTER TE VARIES ~3% ACROSS A RANGE OF AT LEAST 0-85% RH. WE PROPOSE TO RETURN TO HAWAII FOR ADDITIONAL FIELD TESTING OF THIS IMPROVEMENT IN THE SO2 SONDE WHILE KILAUEA IS IN A MORE ACTIVE ERUPTIVE PHASE. THESE LAUNCHES WILL ALSO PROVIDE VALUABLE INFORMATION REGARDING THE VERTICAL STRUCTURE OF THE PLUME WHICH CAN BE USED IN THE EVALUATION OF SATELLITE RETRIEVALS OF SO2. IN ADDITION TO TESTING THE IMPROVED SO2 SONDE WE WILL ALSO DEPLOY MULTIPLE PANDORA INSTRUMENTS TWO FROM UH AND TWO FROM NASA GODDARD TO COLLECT TOTAL COLUMN MEASUREMENTS OF SO2. ONE OF THESE INSTRUMENTS WILL REPLACE THE FAULTY PANDORA AT THE MAUNA LOA OBSERVATORY A KEY LONG-TERM MEASUREMENT SITE IN THE PANDORA NETWORK. ADDITIONAL REMOTE SENSING INSTRUMENTS WILL BE COLLOCATED WITH ONE OF THE PANDORAS TO COLLECT SUPPORTING OBSERVATIONS SUCH AS AEROSOL OPTICAL DEPTHS AND BOUNDARY LAYER HEIGHT MEASUREMENTS. THESE MEASUREMENTS WILL BE USED TO BETTER CONSTRAIN AND INTERPRET THE PANDORA MEASUREMENTS WHICH CAN THEN BE COMPARED TO OMI AND TROPOMI SO2 COLUMN RETRIEVALS.