Impact of Charge Transfer Inefficiency on transit light-curves: A correction strategy for PLATO
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| Format: | Preprint |
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2025
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| _version_ | 1866915869353836544 |
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| author | Mishra, Shaunak Samadi, Reza Bérard, Diane |
| author_facet | Mishra, Shaunak Samadi, Reza Bérard, Diane |
| contents | PLATO is designed to detect Earth-sized exoplanets around solar-type stars and to measure their radii with accuracy better than \(2\%\) via the transit method. Charge transfer inefficiency (CTI), a by-product of radiation damage to CCDs, can jeopardise this accuracy and therefore must be corrected. We assessed and quantified the impact of CTI on transit-depth measurements and developed a correction strategy that restores CTI-biased depths within the accuracy budget. Using a calibration dataset generated with PLATOSim to simulate a realistic stellar field, we modelled the parallel overscan signal as a sum of exponential decays and used least-squares fitting to infer the number of trap species and initial estimates for the release times (\(τ_{r,k}\)). Smearing was modelled with an exponential-plus-constant function and removed on a column-wise basis. We modelled the spatial variation in trap density with a quadratic polynomial in radial distance from the focal-plane center. The polynomial coefficients (\(a_{p,k}\)), the well-fill power index (\(β\)), and the release times (\(τ_{r,k}\)) were adjusted via an iterative application of the extended pixel edge response (EPER) method combined with a CTI correction algorithm, yielding the final calibration model. In the worst-case scenario (8-year mission, high-CTI zone), CTI induced a bias of about \(4\%\) in measured transit depth, reduced to a residual of \(0.06\%\) after correction - well within PLATO's accuracy requirements. From the calibrated parameters, we derived a correction scheme that brought the photometric measurements within PLATO's noise budget, ensuring that the mission's precision requirements are met. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_22092 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Impact of Charge Transfer Inefficiency on transit light-curves: A correction strategy for PLATO Mishra, Shaunak Samadi, Reza Bérard, Diane Earth and Planetary Astrophysics Instrumentation and Methods for Astrophysics PLATO is designed to detect Earth-sized exoplanets around solar-type stars and to measure their radii with accuracy better than \(2\%\) via the transit method. Charge transfer inefficiency (CTI), a by-product of radiation damage to CCDs, can jeopardise this accuracy and therefore must be corrected. We assessed and quantified the impact of CTI on transit-depth measurements and developed a correction strategy that restores CTI-biased depths within the accuracy budget. Using a calibration dataset generated with PLATOSim to simulate a realistic stellar field, we modelled the parallel overscan signal as a sum of exponential decays and used least-squares fitting to infer the number of trap species and initial estimates for the release times (\(τ_{r,k}\)). Smearing was modelled with an exponential-plus-constant function and removed on a column-wise basis. We modelled the spatial variation in trap density with a quadratic polynomial in radial distance from the focal-plane center. The polynomial coefficients (\(a_{p,k}\)), the well-fill power index (\(β\)), and the release times (\(τ_{r,k}\)) were adjusted via an iterative application of the extended pixel edge response (EPER) method combined with a CTI correction algorithm, yielding the final calibration model. In the worst-case scenario (8-year mission, high-CTI zone), CTI induced a bias of about \(4\%\) in measured transit depth, reduced to a residual of \(0.06\%\) after correction - well within PLATO's accuracy requirements. From the calibrated parameters, we derived a correction scheme that brought the photometric measurements within PLATO's noise budget, ensuring that the mission's precision requirements are met. |
| title | Impact of Charge Transfer Inefficiency on transit light-curves: A correction strategy for PLATO |
| topic | Earth and Planetary Astrophysics Instrumentation and Methods for Astrophysics |
| url | https://arxiv.org/abs/2510.22092 |