Project DR-09

Calibration of spectro-polarimetry CRIRES data

The purpose of this project is to develop the CPL-based pipeline recipes to support in particular the CRIRES spectro-polarimetry mode.

References

At the AI Vienna extensive experience exists in high-resolution IR spectroscopy and spectro-polarimetry. Thus we propose to contribute further workforce for 2 aspects related to the polarimetric capabilities of CRIRES:

• calibration issues and establishment of a physical instrument model
• reduction pipeline for spectro-polarimetry  

Applicable instruments and modes

CRIRES, but also other spectro-polarimetry instruments (FORS1, ISAAC, and NACO).
 

Required archive, calibration or observation data

CRIRES polarimetry data


Required algorithm developments

This project could be extended to provide spectro-polarimetry support for other instruments (FORS1, VISIR, ISAAC, and NACO). A set of pipeline recipes for the FORS Imaging and Spectroscopy models is in development at ESO. The structure of this package shall be used for the definition of the CRIRES package. The possibility to provide a set of generic, reusable routines (either as part of the CPL DRS library or as high-level pipeline recipes) should be investigated.

CRIRES has the peculiarity that it uses a de-rotator with quite oblique reflections and has a dichroic mirror, which will add special complications in the sense of strong wavelength dependence of the instrumental polarisation. A rudimentary physical model exists, provided by a student from Vienna two years ago, but it would be highly beneficial to have this improved and tested with data and then used for observations. Specific aspects of the pipeline are that the polarimetric mode basically subtracts pairs of high S/N spectra. The reduction of non-linearities and detector artifacts here is particularly important.

Required software developments

All software will be developed following the guidelines of 1618 document. The software delivery will include in particular the CPL-based recipes, test reports, user documentation and Reflex workflows.

Validation 

The results will be validated against the results of exisiting ESO pipelines (e.g. FORS polarimetry) and against standard polarimetry packages (e.g. Starlink POLPACK package).