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Celebrating Twenty Years of the HST’s Advanced Camera for Surveys: Calibration Update

Presentation #206.03 in the session New Mission Concepts — iPoster Session.

Published onJun 29, 2022
Celebrating Twenty Years of the HST’s Advanced Camera for Surveys: Calibration Update

The Advanced Camera for Surveys (ACS) has been a workhorse Hubble Space Telescope (HST) imager for over twenty years, subsequent to its Servicing Mission 3B installation in 2002. The once defunct ACS Wide Field Channel (WFC) has now been operating over twice as long (>13yrs) since its Servicing Mission 4 (SM4) repair than it had originally operated prior to its 2007 failure. Despite the accumulating radiation damage to the WFC CCDs during their long stay in low Earth orbit, ACS continues to be heavily exploited by the HST community as both a prime and a parallel detector. ACS observations have factored in to nearly half of all HST-related refereed journal articles in recent years, and have enabled an average of 352 refereed journal articles per year from 2002 through 2020. Those 6693 ACS-related papers represent over 36% of the total lifetime output by HST, which was operating for twelve years before ACS installation.

We present results from the latest studies of detector performance for both WFC and the ACS Solar Blind Channel (SBC), including long-term monitoring of WFC and SBC dark current and WFC readout noise. We also advertise updated ACS documentation and software tools for the user community. Highlights include: 1) long-term monitoring of the WFC tungsten lamp and WFC post-flash LED brightness, the latter employed to mitigate degraded charge-transfer efficiency (CTE) of the WFC CCDs; 2) updated analysis of WFC PSF broadening during CCD readout due to degraded CTE, as well as refinements to both pixel-based and photometric corrections for WFC CTE; 3) a comparison of Exposure Time Calculator (ETC) estimated versus observed WFC sky background levels filter-by-filter, from twenty years of external exposures by Guest Observer and calibration programs; and 4) the commissioning update for a new ACS operating mode — high-precision optical/near-IR spectropolarimetry at high spatial resolution (~0.1 arcsec) using paired WFC grism and polarizer filters.

This poster also includes links to the press releases by STScI, NASA, and ESA, and to the informational banner by the ACS Instrument Team, all celebrating the 20th anniversary of ACS installation aboard HST on 7 March 2002.

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