Diffraction in the ASPIICS coronagraph: Observations and modeling
Abstract
Context . ASPIICS is a giant-baseline visible light solar coronagraph, which relies on the millimetric positioning performance of the precision formation flying Proba-3 mission of the European Space Agency. Proba-3 was launched on 5 December 2024, and since then ASPIICS has observed the solar corona with the field of view (1.1–3) R ⊙ . Aims . Diffraction, in particular diffraction of solar disk light on the external occulter, is known to provide a major source of stray light in coronagraphs. Our aims were to analyze diffracted light visible in ASPIICS images, to compare it with the analytical-numerical diffraction model reported earlier, and to fine-tune the model. Methods . We compared the diffraction effects visible in the ASPIICS data with simulated diffraction images; in particular, we compared the geometrical properties and the radiometric signal. The properties of the diffraction described in previous works suggest how to fine-tune the model in order to achieve a better correspondence with the observations. Results . Early ASPIICS observations, where diffraction is pronounced, fully confirm all the qualitative properties of diffracted light suggested by the model. After fine-tuning the model we found a quantitative correspondence of the level of 30–50%, depending on the configuration. Conclusions . The performed analysis allows us to validate our analytical-numerical model and justify the assumptions, and to estimate the contribution of the diffracted light in the ASPIICS images. Over most of the field of view the diffracted light is two orders of magnitude below the coronal signal.
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BibTeX
@article{shestov2026diffraction,
title = {{Diffraction in the ASPIICS coronagraph: Observations and modeling}},
author = {S. Shestov and A. N. Zhukov and R. Rougeot and C. Aime and B. Bourgoignie and L. Dolla and N. Britavskiy and S. Fineschi and S. Gunár and P. Lamy and M. Mierla and H. Peter and P. Rudawy and K. Tsinganos},
journal = {Astronomy \& Astrophysics - A\&A},
year = {2026},
month = nov,
doi = {10.1051/0004-6361/202659671},
url = {https://hal.science/hal-05849842v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Diffraction in the ASPIICS coronagraph: Observations and modeling
AU - S. Shestov
AU - A. N. Zhukov
AU - R. Rougeot
AU - C. Aime
AU - B. Bourgoignie
AU - L. Dolla
AU - N. Britavskiy
AU - S. Fineschi
AU - S. Gunár
AU - P. Lamy
AU - M. Mierla
AU - H. Peter
AU - P. Rudawy
AU - K. Tsinganos
PY - 2026
DA - 2026/11/03
JO - Astronomy & Astrophysics - A&A
DO - 10.1051/0004-6361/202659671
UR - https://hal.science/hal-05849842v1
AB - Context . ASPIICS is a giant-baseline visible light solar coronagraph, which relies on the millimetric positioning performance of the precision formation flying Proba-3 mission of the European Space Agency. Proba-3 was launched on 5 December 2024, and since then ASPIICS has observed the solar corona with the field of view (1.1–3) R ⊙ . Aims . Diffraction, in particular diffraction of solar disk light on the external occulter, is known to provide a major source of stray light in coronagraphs. Our aims were to analyze diffracted light visible in ASPIICS images, to compare it with the analytical-numerical diffraction model reported earlier, and to fine-tune the model. Methods . We compared the diffraction effects visible in the ASPIICS data with simulated diffraction images; in particular, we compared the geometrical properties and the radiometric signal. The properties of the diffraction described in previous works suggest how to fine-tune the model in order to achieve a better correspondence with the observations. Results . Early ASPIICS observations, where diffraction is pronounced, fully confirm all the qualitative properties of diffracted light suggested by the model. After fine-tuning the model we found a quantitative correspondence of the level of 30–50%, depending on the configuration. Conclusions . The performed analysis allows us to validate our analytical-numerical model and justify the assumptions, and to estimate the contribution of the diffracted light in the ASPIICS images. Over most of the field of view the diffracted light is two orders of magnitude below the coronal signal.
SN - 0004-6361
SN - 1432-0746
ER -