The Time-Dependent Sensitivity Correction of the COS/FUV Cenwaves G130M/1055 and G130M/1096
Abstract
We present the time dependent sensitivity (TDS) corrections for the G130M/1055 and G130M/1096 cenwaves, otherwise known as the blue modes at lifetime position 2 (LP2). The time dependent sensitivity (TDS) corrections are derived by monitoring calibrator white dwarfs every 2 months and fitting a piecewise linear function to the monitoring data binned in wavelength as a function of time, for each detector segment. Slopes and intercepts in wavelength and time bins were derived in the fitting process, these slopes were then averaged for cenwaves 1055 and 1096 and smoothed with a 60A kernel. ˚ For the analysis, TDS monitoring data were included from the start of monitoring in 2012 until March 2020, with a subsequent minor update which included four additional sets of monitoring data up to October 2020. Comparison of the data with the CALSPEC models for WD0308-565 and GD71 showed that with the new TDS correction there were no significant residuals with wavelength or time. The time dependent flux calibration is within the 5% absolute and 2% relative relative flux calibration requirements for most bins as a function of wavelength and time, bringing the blue modes flux calibration in line with the standard modes.
- Publication:
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Instrument Science Repor COS 2021-8
- Pub Date:
- September 2021
- Bibcode:
- 2021cos..rept....8K
- Keywords:
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- HST;
- Hubble Space Telescope;
- STScI;
- Space Telescope Science Institute;
- COS;
- Cosmic Origins Spectrograph