THE TWITTER DATA SET IS POTENTIALLY A RICH SOURCE OF INFORMATION FOR SCIENCE APPLICATIONS. OVER THE PAST SEVERAL YEARS AS RESOURCES PERMIT WE HAVE BEEN INVESTIGATING THE FEASIBILITY OF EXTRACTING FROM THE TWITTER DATA STREAM--WITHOUT ACTIVELY SOLICITING INPUTS-- USEFUL INFORMATION FOR APPLICATION TO NASA PRECIPITATION RESEARCH. THERE HAVE BEEN SIMILAR USES OF TWITTER AND OTHER SOCIAL MEDIA MOSTLY RELATED TO NATURAL HAZARDS MONITORING AND MANAGEMENT IN WHICH THE PARTICIPANTS KNOWINGLY AND ACTIVELY CONTRIBUTE. TWO EXAMPLES ARE THE SNOWTWEETS PROJECT (HTTP://SNOWCORE.UWATERLOO.CA/SNOWTWEETS/) AND METEOROLOGICAL PHENOMENA IDENTIFICATION NEAR THE GROUND (MPING; HTTP://MPING.NSSL.NOAA.GOV/). OTHER SUCH USES DEAL WITH EARTHQUAKES VOLCANOES AIR POLLUTION ETC. BOTH CASES OF PASSIVE AND ACTIVE ENGAGEMENTS BY PARTICIPATING CITIZEN SCIENTISTS HOLD POTENTIAL FOR E.G. AUGMENTING VALIDATION PROGRAMS OF NASA SATELLITE PRECIPITATION MISSIONS. IN THE PASSIVE CASE WE HAVE EXPERIMENTED WITH LISTENING TO THE TWITTER STREAM FOR RAIN AND RELATED TWEETS IN DIFFERENT LANGUAGES AND MAPPING THEIR RESULTING DISTRIBUTION. OUR APPROACH SEEMS PROMISING FOR DEMONSTRATING NOT ONLY A UNIQUE APPLICATION OF TWITTER BUT ALSO A DEEPER POWER RESIDING WITHIN THE TWITTER DATA SET. THE TIME-VARYING SET OF RAIN TWEETS E.G. CAN BE THOUGHT OF AS AN ORGANIC NETWORK OF RAIN GAUGES. ISSUES THAT WE NEED TO MORE FULLY ADDRESS INCLUDE (1) FILTERING FOR QUALITY TWEETS (2) GEOLOCATION QUALITY AND (3) IRREGULAR LOCATIONS OF TWEETS. IN THE ACTIVE CASE WE HAVE CONDUCTED VERY PRELIMINARY EXPERIMENTS TO EVALUATE DIFFERENT METHODS OF ENGAGING WITH POTENTIAL PARTICIPANTS. FOR EXAMPLE WE HAVE REPLIED TO RAIN TWEETS WITH TRMM IMAGES GENERATED BY NASA GIOVANNI CENTERED ON THE TWEET LOCATIONS. (FOR THE PURPOSE OF THE EXPERIMENT OUR REPLIES ACTUALLY WERE DIRECTED TO A SPECIALLY CREATED TWITTER ACCOUNT OF OURS.) WE HAVE ALSO CONSIDERED USING ONLINE GAMES TO RECRUIT POTENTIAL ACTIVE PARTICIPANTS. WE BELIEVE OUR APPROACH WHICH DOES NOT REQUIRE PARTICIPANTS TO EXPLICITLY SIGN UP TO CONTRIBUTE AS CITIZEN SCIENTISTS EVEN IN THE ACTIVE CASE IS MORE ROBUST. PARTICIPANTS WHO ROUTINELY USE TWITTER WOULD CONTINUE TO DO SO. THE SCIENCE RATIONALE FOR MINING RAIN AND RELATED TWEETS IS TO POTENTIALLY OBTAIN A WIDESPREAD VIEW OF RAIN OCCURRENCE. ASSUMING THE TWEETS ARE OF REASONABLE QUALITY THE TWO MAIN SCIENCE ISSUES ARE (1) THE RESULTS ARE MOSTLY ONLY QUALITATIVE (NO RAIN RATE INFORMATION) AND (2) THE RESULTS ARE ONLY POSITIVE (NO DIRECT NO-RAIN REPORTS) THOUGH THERE ARE POSSIBLE WAYS TO MITIGATE THESE ISSUES. CURRENTLY THE RAIN/NO-RAIN BOUNDARY IS SUBJECT TO CONSIDERABLE UNCERTAINTY WHEN GAUGE STATIONS OR SATELLITE OVERPASSES ARE SPARSE. RAIN TWEETS COULD HELP CONSTRAIN THIS BOUNDARY. THE DEVELOPMENT OF SUCH AN APPLICATION OF TWITTER WOULD TAKE PLACE MAINLY IN THE U.S. WHERE THERE IS A HIGH DENSITY OF DATA. ACTUAL APPLICATIONS WOULD BE MOSTLY OUTSIDE THE U.S. BECAUSE IN MANY OF THOSE REGIONS THE RELEVANT MEASUREMENTS ARE FREQUENTLY SPARSE INACCESSIBLE OR NON-EXISTENT. OUR PROPOSED PROJECT GOAL IS TO MINE THE TWITTER DATABASE TO AUGMENT THE VALIDATION PROGRAM OF THE NASA GLOBAL PRECIPITATION MEASUREMENT (GPM) MISSION. OUR PROJECT WOULD ALSO HELP EXTEND THE APPLICATION REALM OF TWITTER AS A PLATFORM FOR CITIZEN SCIENCE TO SIMILAR SCIENCE MISSIONS IN GENERAL. SUCH A DEMONSTRATION OF THE VALUE OF TWITTER TO THE SCIENCE RESEARCH COMMUNITY WOULD