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The Space Telescope Imaging Spectrograph's (STIS) BAR5 coronagraphic occulterwas designed to provide high-contrast, visible-light, imaging in close (>=0.15") angular proximity to bright point-sources. This is the smallest innerworking angle (IWA) possible with HST's suite of coronagraphically augmentedinstruments through its mission lifetime. The STIS BAR5 image plane occulter,however, was damaged (bent and deformed) pre-launch and had not been enabledfor GO science use following the installation of the instrument in 1997, duringHST servicing mission SM2. With the success of the HST GO 12923 program,discussed herein, we explored and verified the functionality and utility of theBAR5 occulter. Thus, despite its physical damage, with updates to the knowledgeof the aperture mask metrology and target pointing requirements, a robustdetermination of achievable raw and PSF-subtracted stellocentric imagecontrasts and fidelity was conducted. We also investigated, and herein reporton, the use of the BAR10 rounded corners as narrow-angle occulters and compareIWA vs. contrast performance for the BAR5, BAR10, and Wedge occulters. Withthat, we provide recommendations for the most efficacious BAR5 and BAR10 useon-orbit in support of GO science. With color-matched PSF-template subtractedcoronagraphy, inclusive of a small (+/- 1/4 pixel) 3-point cross-bar ditheringstrategy we recommend, we find BAR5 can deliver effective ~ 0.2" IWA imagecontrast of ~ 4 x 10^-5 pixel^-1 to ~ 1 x 10^-8 pixel^-1 at 2". With thepointing updates (to the PDB SIAF.dat file and/or implemented through APT) thatwe identified, and with observing strategies we explored, we recommend the useof STIS BAR5 coronagraphy as a fully "supported" capability for unique GOscience.

Enabling Narrow(est) IWA Coronagraphy with STIS BAR5 and BAR10 Occulters