Presentation #350.01 in the session “Hubble Space Telescope Updates”.
The Cosmic Origins Spectrograph (COS) was installed on the Hubble Space Telescope (HST) in 2009. After over a decade of operations, both the far-ultraviolet (FUV) and near-ultraviolet (NUV) channels remain scientifically productive and continue to provide high-quality spectroscopic capabilities. We present recent calibration work of interest to future HST proposers and all COS users. Specifically, COS FUV blue mode observations (i.e. G130M spectra centered at 1055 and 1096 Angstroms) have been recalibrated, with improvements to the flux calibration, time-dependent sensitivity (TDS) calibration, and wavelength calibration. Additionally, we describe the delivery of a new FUV TDS reference file (TDSTAB). The new TDSTAB is a hybrid cenwave dependent file where monitored cenwaves have slopes determined only from the monitoring of that cenwave and unmonitored cenwaves have slopes that continue to be averaged as before. Further, FUV TDS models for the standard modes have been updated to include a temporal breakpoint at 2019.0 to account for changes in the slope since 2019. Finally, we discuss recent improvements in the CalCOS pipeline which reduce uncertainties in datasets with low count rates.