| Issue |
A&A
Volume 668, December 2022
|
|
|---|---|---|
| Article Number | A151 | |
| Number of page(s) | 17 | |
| Section | Astronomical instrumentation | |
| DOI | https://doi.org/10.1051/0004-6361/202243466 | |
| Published online | 16 December 2022 | |
Data reduction and restoration of spectropolarimetric microlensed hyperspectral imager data
Max-Planck Institute for Solar System Research,
Justus-von-Liebig-Weg 3,
37077
Göttingen, Germany
e-mail: vannoort@mps.mpg.de
Received:
3
March
2022
Accepted:
20
October
2022
Context. A microlensed hyperspectral imager (MiHI) is an integral field spectrograph based on a double-sided microlens array.
Aims. To convert the raw data frames of such an instrument to hyperspectral cubes, and restore them to high-resolution science-ready Stokes data, a new kind of data reduction procedure is required.
Methods. An optimized ad hoc transfer map of a MiHI prototype was used to convert the raw data into raw hyperspectral form. The transfer map was modified to match the position of the image on the detector, which was found to drift considerably during the course of an observing day. The determination of this position was used to move the recorded flat-field images to the position of the observation, which was found to be a critical step in the accurate gain correction of the raw data cubes. The converted data were found to be suitable for image restoration but still contained unwanted polarimetric structure that needed to be removed.
Results. The extracted and restored data were found to be of a similar spatial resolution as the equivalent data from the context imager, while retaining a spectral resolution of approximately 300 000. The noise properties of the raw data were determined by the photon statistics and were found to be consistent with the estimated transparency of the instrument and the integration time of the image sensor. As for all image-restored data, the noise properties of the restored data were found to be dependent on the instrumental and atmospheric point spread function. An attempt to compare the data to other similar data suggested that the data had a spectral and spatial information content comparable to that of a Hinode spectro-polarimetric scan, but with a higher spatial resolution and a temporal cadence of approximately 10s.
Key words: techniques: high angular resolution / techniques: image processing / techniques: imaging spectroscopy / techniques: polarimetric / methods: data analysis / methods: observational
© M. van Noort and H.-P. Doerr 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe-to-Open model.
Open Access funding provided by Max Planck Society.
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