  Observations utilizing the ultraviolet capabilities of the Cosmic Origin
Spectrograph (COS) onboard the Hubble Space Telescope are of unique value to
the astronomy community. Spectroscopy down to 900 A with COS has enabled new
science areas. However, contrary to the situation at longer wavelengths, these
observations are limited by detector background noise. The background
correction currently applied by the standard calibration pipeline (CalCOS) is
not optimized for faint targets, limiting the scientific value of low
signal-to-noise observations. In this work we investigate a possible dependence
of the variations of the dark rate in both segments of the COS far-ultraviolet
(FUV) detector on time, detector high voltage (HV), and solar activity. Through
our analysis we identified a number of detector states (on a configuration
basis, e.g., HV and segment) characterizing the spatial distribution of dark
counts, and created superdarks to be used in an optimized 2-dimensional (2D)
background correction. We have developed and tested Another COS Dark Correction
(ACDC), a dedicated pipeline to perform a 2D background correction based on
statistical methods, producing background-corrected and flux-calibrated
spectra. While our testing of ACDC showed an average improvement in S/N values
of ~10%, in a few cases the improvements in S/N reached 60% across the whole
wavelength range of individual segments.
