WE PROPOSE TO CONDUCT STUDIES OF COMETS OBSERVED BY THE ESA/NASA SOLAR HELIOSPHERIC OBSERVATORY (SOHO) AND THE NASA SOLAR TERRESTRIAL RELATIONS OBSERVATORY (STEREO). ALTHOUGH SOHO AND STEREO ARE BEST KNOWN FOR THEIR MASSIVE (>3400 COMETS) AND UNIQUE DATASET OF "SUNGRAZING" COMET DISCOVERIES THEY HAVE ALSO SERENDIPITOUSLY IMAGED DOZENS OF NON-SUNGRAZING COMETS DISCOVERED BY OTHER TELESCOPES. THESE NON-SUNGRAZING COMETS HAVE GENERALLY GONE UNSTUDIED OWING IN LARGE PART TO THE DIFFICULTY OF USING THE DATA WITHOUT SPECIALIZED SOFTWARE. THE SOHO AND STEREO DATA OF THESE COMETS ARE INVALUABLE FOR THEIR UNIQUE VIEWING GEOMETRIES AT SOLAR ELONGATIONS GENERALLY INACCESSIBLE TO TRADITIONAL OBSERVATORIES. FURTHERMORE MANY OF THE OBSERVATIONS ARE MADE AT HELIOCENTRIC DISTANCES BELOW 1 AU WHEN THE COMETS ARE MOST ACTIVE NEAR PERIHELION. WE HAVE DEVELOPED EXTENSIVE SOFTWARE ROUTINES TO REDUCE AND ANALYZE SOHO AND STEREO DATA UNDER PREVIOUS NASA FUNDING. WE WILL EXPLOIT THESE EXISTING ROUTINES AND OUR INTIMATE EXPERIENCE WITH SOHO AND STEREO TO CONDUCT TWO PROJECTS THAT WILL YIELD NOVEL INSIGHT INTO THE COMPOSITION AND EVOLUTION OF COMETS: 1. PERFORM PHOTOMETRY OF COMETS OBSERVED IN HIGHLY FORWARD-SCATTERING GEOMETRIES TO COMPILE THE MOST EXTENSIVE AND HOMOGENEOUS SUCH DATASET IN EXISTENCE. USE THIS DATASET TO CONSTRAIN FORWARD-SCATTERING MODELS YIELDING AN IMPROVED UNDERSTANDING OF THE PHYSICAL PROPERTIES OF DUST GRAINS IN COMET COMAE. 2. PERFORM PHOTOMETRY OF "NORMAL" (NON-SUNGRAZING) COMETS TO FILL GAPS IN THEIR SECULAR LIGHTCURVES WHEN THEY WERE OTHERWISE UNOBSERVED. THIS WILL PROVIDE QUANTIFIABLE MEASURES OF ACTIVITY FOR INDIVIDUAL COMETS INCLUDING PEAK BRIGHTNESS RATES OF BRIGHTENING AND FADING ASYMMETRIES AROUND PERIHELION AND STRENGTH OF ANY OUTBURSTS. THE ENSEMBLE OF DATA WILL ALLOW COMPARATIVE STUDIES BETWEEN SUBPOPULATIONS AND INVESTIGATIONS INTO ONGOING EVOLUTIONARY PROCESSES. AN ADDITIONAL BENEFIT OF THE PROPOSED WORK IS TO MAKE THE SOHO AND STEREO DATASETS ACCESSIBLE TO LESS EXPERIENCED USERS. BY ARCHIVING REDUCED AND CALIBRATED IMAGES AND PHOTOMETRY WITH THE PLANETARY DATA SYSTEM (PDS) FOR ALL COMETS STUDIED THIS WORK WILL OPEN THE RICH SOHO AND STEREO DATASETS TO THE BROADER COMET COMMUNITY. THIS PROPOSAL IS TIMELY BECAUSE THE DATASET OF NON-SUNGRAZING COMETS OBSERVED BY SOHO AND STEREO HAS REACHED A CRITICAL MASS TO PERMIT MEANINGFUL COMPARISONS BETWEEN DYNAMICAL POPULATIONS OF COMETS (SHORT PERIOD VERSUS LONG PERIOD/OORT CLOUD COMETS). ALSO SEVERAL SHORT PERIOD COMETS HAVE BEEN OBSERVED ON MULTIPLE APPARITIONS ALLOWING US TO INVESTIGATE EVOLUTIONARY TRENDS IN THESE OBJECTS. FURTHERMORE THE COMING ERA OF LARGE SURVEY TELESCOPES E.G. ZWICKY TRANSIENT FACILITY (ZTF) AND LARGE SYNOPTIC SURVEY TELESCOPE (LSST) WILL ENABLE SIMILAR STUDIES OF LARGE NUMBERS OF COMETS BEYOND 1 AU BUT WILL OBTAIN FEW OBSERVATIONS AT HELIOCENTRIC DISTANCES BELOW 1 AU. MOST COMETS IN OUR SAMPLE REACH PERIHELION BELOW 1 AU SO OUR PROPOSED WORK WILL PROVIDE VITAL CONTEXT FOR UNDERSTANDING EVOLUTIONARY TRENDS IN THE COMET POPULATION WITH PERIHELION DISTANCE.