IRDAP (IRDIS Data reduction for Accurate Polarimetry) is a highly-automated end-to-end pipeline to reduce SPHERE-IRDIS polarimetric data using polarimetric differential imaging (PDI). Its core feature is the model-based correction method of the instrumental polarization effects as described in van Holstein et al. (2020). IRDAP handles data taken both in field- and pupil-tracking mode and using the broadband filters Y, J, H and Ks. Data taken with the narrowband filters can be reduced as well, although with a somewhat worse accuracy. For pupil-tracking observations IRDAP can additionally apply angular differential imaging.

Reducing data with IRDAP is very straightforward and does not require the user to do any coding or have knowledge of Python (IRDAP is written for Python 3.6 and higher). IRDAP is simply run from a terminal with only a few commands and uses a configuration file with a limited number of input parameters. Within several minutes, IRDAP performs a complete data reduction from raw data to final data products.


If you use IRDAP for your publication, please cite our papers.


Three examples of data sets reduced with IRDAP: the circumstellar disk of PDS 70 including its inner disk that polarizes the central star (Keppler et al. 2018), the circumstellar disk and polarized companion of CS Cha (Ginski et al. 2018) and the circumstellar disk of T Cha (Pohl et al. 2017; van Holstein et al. 2020).

IRDAP yields a multitude of improvements for polarimetric observations of circumstellar disks: it enables us to accurately study the morphology of disks, measure non-azimuthal polarization and determine scattering phase functions and particle properties. Because IRDAP discerns instrumental polarization from stellar polarization, it is a vital tool for accurate radiative transfer modeling of disks and enables the detection of unresolved (inner) disks and the measurement of the polarization of substellar companions. Finally, IRDAP enables accurate data reduction for targets that cannot be reduced with the conventional data-reduction methods (because there is no bright star in the field of view), such as solar system objects.


Copyright notice:

The IRDAP Python module is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 3 of the License.

The IRDAP Python module is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with the IRDAP Python module. If not, see