IPMG: STIS Calibration Enhancement

IPMG STIS Calibration Enhancement

  • Aim: To improve aspects of the existing STIS calibration pipeline which benefit from physically motivated corrections.
  • Supported by an ESA/NASA MoU
  • Current areas of investigation:
    • Wavelength Calibration: Our model based approach to improve the quality of STIS pipeline output utilizes the predictive power of a physically correct spectral ray trace model of each STIS spectral mode to feed the pipeline with the "where is what" information required for the spectral extraction. This model corrrectly predicts the movements and shape changes of orders and spatial information on the 2D detector array with modifications of tilt agles and positions of all the optical elements. More...
    • Line List for Calibration Lamps: The ST-ECF lamp project studies hollow cathode calibration lamps as they are used onboard the HST. We have measured the spectra of Pt/Cr-Ne lamps in order to obtain accurate and reliable wavelengths for all emission lines between 115 and 320 nm. (STIS Echelle modes). Extensive laboratory measurements were performed at the National Institute of Standards and Technology (NIST). The new line list is being used in conjunction with the physical instrument model of STIS which is employed to derive an improved wavelength calibration as part of the STIS-CE effort. Further, we attempt to gain a better understanding of the performance of such lamps and the physical processes involved in their long term operations. To this end we studied the dependence of the spectrum upon current and age and the tolerances of alignment. Our findings also constitute important lessons for the design and operations of future UV and optical spectrographs in space. More...
    • Charge Transfer Inefficiency: We have developed a model of the readout process of the STIS CCD which is able to reproduce the effects of CTI seen in STIS CCD imaging and spectroscopic data. Using this model we have implemented a pre-processor for CALSTIS which removes these CTI effects prior to further processing. More...

  • Links:

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