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Long-period comet nuclei are volatile rich products of accretion in the protoplanetary disk of the Sun comma preserved at about 10 K in the Oort cloud. They include some of the most primitive macroscopic objects in the solar system. We now know that comet nuclei spontaneously and suddenly disintegrate and that disintegration probably dominates sublimation as the main destructive process operating on these bodies when in the inner solar system. Crucially comma disintegration may account for the long-recognized ''fading problem.. discovered by Oort in 1950doublePoint comets fade because they fall apart comma not because they run out of ice. Unfortunately comma our confidence that disintegration is important is not matched by an understanding of the process or its cause. This is because disintegrations are unpredictable comma sudden comma and difficult to observe. Proposed models center around internal pressure build-up comma explosion of amorphous ice comma and centripetal disruption caused by outgassing torques comma but we do not possess the high quality (resolution comma sensitivity and temporal resolution) data needed to determine what is really happening. C-2021 A1 began disintegration in early 2022 March comma providing a rare opportunity to study a disintegration with the full power of HST. We propose an efficient comma 4 orbit DDT observation comma with 3 orbits scheduled early to assess the fragment field and measure size comma velocity and acceleration distributions comma and a single orbit in June to examine the distribution of material perpendicular to the orbit plane. Only by obtaining this type of high resolution comma high sensitivity comma time-resolved data can we hope to characterize and understand cometary disintegration.