Alison: NOTE: Revision 4: Nov 21, 2018: I have increased the exposure times from 712 to 730 sec for all targets, (still keeping within the 9 orbits), and I have revised the nine target locations slightly in order to increase the value of these images in regard to the visibility of the remnant's outer ejecta knots relative to previous HST images. -1964854523 ----- Attempting Submission 1 (Wed Sep 05 19:41:55 GMT 2018) ----- HST Phase II Proposal 15515 (HST Phase II Proposal 15515 V3.apt) successfully submitted. Receipt: # 15515-1 ----- Attempting Submission 2 (Wed Sep 26 14:51:28 GMT 2018) ----- ----- Attempting Submission 3 (Wed Nov 21 22:58:45 GMT 2018) ----- An HST Survey of Cassiopeia A's Reverse Shock, High-Velocity Ejecta, and Shocked Clouds of Pre-SN Mass Loss The young Galactic supernova remnant Cassiopeia A (Cas A) provides us with the clearest look at the properties and explosion dynamics of a high mass, core-collapse supernova (CCSN). With an explosion date around 1670, Cas A is the youngest Galactic core-collapse SNR known and, at an estimated distance of 3.4 kpc, it is also among the closest. Cas A's main shell ejecta knots are typically 0.1 - 0.5 arcsec in size and can show emission and morphological changes on timescales of just a few months. No other remnant, with the exception of SN 1987A, shows such rapid optical changes across large portions of its structure. Here we propose a new, complete optical survey of Cas A, the first since 2004, in order to measure the velocity and asymmetry of Cas A's reverse shock front across the whole remnant and map the distribution of its high-velocity outer ejecta, particularly in regions which align to the motion of the central compact source. Halpha images of the remnant's shocked CSM clumps will also provide strong tests of shock-cloud models across a broad range of cloud densities and sizes. These data will constitute a rich and unique archive both for Cas A and the general study of high mass CCSNe. This program is to image the young supernova remnant, Cassiopeia A (Cas A) in three filters: F475W, F625W, and F658N. Nine separate pointings are need in order to cover the entire remnant images. Images in the three filters will be taken at each pointing during one CVZ orbit, totaling nine CVZ orbits. A second set of identical images will be taken roughly one year apart in Cycle 26. The second epoch images is required to discern ejecta knots from stars or distant galaxies via their high proper motions. Cas A lies at the very southern edge of the HST's Continous Viewing Zone (CVZ) and the use of the full 96 minute HST orbit and hence observing time allows for a much more compact and efficient observing program. Similar CVZ imageing programs of Cas A have been done in the past, despite the few days that Cas A is observable in Hubble's CVZ. Note: We have decided to omit the H-alpha imaging in this second set of images and concentrate on the F625W images. This allows two extra images for each target region plus longer exposure times (712 sec vs 510 sec) to obtain much deeper images. NOTE: Revision 4: Nov 21, 2018: Have increased the exposure times from 712 to 730 sec for all targets, and have revised the nine target locations in order to increase visibility of the remnant's outer ejecta knots relative to previous HST images. Stellar Physics 6 false false false false false false false SUPPORTED ISM EJECTA EMISSION LINE NEBULA SHOCK FRONT SNR YES J2000 J2000 ISM EJECTA EMISSION LINE NEBULA SHOCK FRONT SNR YES J2000 J2000 ISM EJECTA EMISSION LINE NEBULA SHOCK FRONT SNR YES J2000 J2000 ISM EJECTA EMISSION LINE NEBULA SHOCK FRONT SNR YES J2000 J2000 ISM EJECTA EMISSION LINE NEBULA SHOCK FRONT SNR YES J2000 J2000 ISM EJECTA EMISSION LINE NEBULA SHOCK FRONT SNR YES J2000 J2000 ISM EJECTA EMISSION LINE NEBULA SHOCK FRONT SNR J2000 J2000 ISM EJECTA EMISSION LINE NEBULA SHOCK FRONT SNR YES J2000 J2000 ISM EJECTA EMISSION LINE NEBULA SHOCK FRONT SNR YES J2000 J2000 WFC3/UVIS Imaging No No F475W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F657N WFC3/UVIS Imaging No No F475W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F657N WFC3/UVIS Imaging No No F475W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F657N WFC3/UVIS Imaging No No F475W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F657N WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F657N WFC3/UVIS Imaging No No F475W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F657N WFC3/UVIS Imaging No No F475W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F657N WFC3/UVIS Imaging No No F475W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F657N WFC3/UVIS Imaging No No F475W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F657N POS-TARG MOSAIC DITHER 3 2.4 WFC3-UVIS-MOS-DITH-LINE false true 0.119 2 85.754 POS-TARG WFC3-UVIS-MOS-DITH-LINE 33.606 1 true Hst Same orient constraint links visits (01 02 03) The scheduling data was generated by CASM 26.2. 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