0 Assigned ID: 338 ----- Attempting Submission 1 (Fri Aug 17 18:22:41 GMT 2018) ----- High-precision astrometry is in the process of revolutionizing our understanding of the local universe. HST's contribution to this endeavor has been tremendous and complements that of the dedicated astrometry mission Gaia. The astrometric success of HST has been achieved due to a dedicated effort in calibrating instruments such as ACS/WFC and WFC3/UVIS. Here it is proposed that a comprehensive astrometric calibration of WFPC2 be undertaken, thus expanding the time baseline of HST proper-motion studies by 10-15 years and impacting areas of research that are currently very challenging, such as proper-motion measurements in globular cluster cores. The proposed calibration process will make use of all appropriate images in filters F555W, F606W and F814W (of the order of thousands of exposures) over the life span of WFPC2. Gaia DR2 and HST standard astrometric catalogs (based on other cameras) will be used to map both low- and high-frequency distortion features, as well as CTE and possible manufacturing defects in WFPC2. Corrections for these will be developed that are functions of time, filter, and other observing parameters of the WFPC2 data. The outcome of the project will be a calibration methodology, code to apply the astrometric corrections, a WFPC2 position catalog, and proper-motion studies of two globular cluster cores, 47 Tuc and NGC 6341. Stellar Populations 0 Legacy false false false false SUPPORTED