Characterization of the UV radiometric calibration for the TROPOMI operational ozone profile retrieval algorithm

Di Pede, Serena; Loots, Erwin; van der Plas, Emiel; Sneep, Maarten; van Amelrooy, Edward; van Hoek, Mirna; ter Linden, Mark; Ludewig, Antje; Keppens, Arno; Veefkind, J. Pepijn

doi:10.5194/egusphere-2025-2167

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https://doi.org/10.5194/egusphere-2025-2167

Preprints

17 Jul 2025

| 17 Jul 2025

Characterization of the UV radiometric calibration for the TROPOMI operational ozone profile retrieval algorithm

Serena Di Pede, Erwin Loots, Emiel van der Plas, Maarten Sneep, Edward van Amelrooy, Mirna van Hoek, Mark ter Linden, Antje Ludewig, Arno Keppens, and J. Pepijn Veefkind

Abstract. The European Space Agency (ESA) Sentinel-5 Precursor (S5P) is a low Earth orbit polar satellite carrying the single payload instrument TROPOspheric Monitoring Instrument (TROPOMI). Since its launch on 13 October 2017, the S5P mission has been acquiring almost 7 years of nadir ozone profile data, retrieved from the UV spectral bands 1–2 (270–330 nm). The retrieval algorithm of the ozone profile can be strongly affected by systematic effects in the measured radiance, and absolute calibration of the input spectra is necessary. In this study, we characterize the TROPOMI bands 1–2 radiometric bias in comparison with simulations obtained with the Determining Instrument Specifications and Analysing Methods for Atmospheric Retrieval (DISAMAR) radiative transfer model. To account for these systematic effects, a radiometric correction (soft-calibration) is applied to the input measurements, which results in the reduction of the spectral reflectance fit residuals of 20–30 %, improved precision of the integrated total and tropospheric ozone columns of 10–15 % and a reduction of along-track orbit artifacts. Together with the analysis of the in-flight calibration measurements, the soft-calibration correction spectra provide also useful insights for the improvement of the instrument radiometric calibration. Therefore, bands 1–2 measurements have been reprocessed specifically for this study, with improvements regarding the detector straylight and background signal correction algorithms, to investigate the impact of the updates into the TROPOMI bands 1–2 radiometric bias. The new soft-calibration correction spectra, obtained with the reprocessed bands 1–2 measurements, show significantly reduced magnitude (around 15–20 %, especially in band 1) and also less across-track position and spectral/temporal biases. The new soft-calibration will be part of ESA’s next official ozone profile algorithm version 2.9.0, coordinated with L1b update to processor version 3.0.0, and used for the second TROPOMI mission reprocessing.

Received: 08 May 2025 – Discussion started: 17 Jul 2025

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Journal article(s) based on this preprint

17 Mar 2026

Characterization and improvements of the UV radiometric calibration for the TROPOMI operational ozone profile retrieval algorithm

Serena Di Pede, Erwin Loots, Antje Ludewig, Emiel van der Plas, Edward van Amelrooy, Mirna van Hoek, Maarten Sneep, Mark ter Linden, Arno Keppens, and J. Pepijn Veefkind

Atmos. Meas. Tech., 19, 1875–1899, https://doi.org/10.5194/amt-19-1875-2026,https://doi.org/10.5194/amt-19-1875-2026, 2026

Short summary

Serena Di Pede, Erwin Loots, Emiel van der Plas, Maarten Sneep, Edward van Amelrooy, Mirna van Hoek, Mark ter Linden, Antje Ludewig, Arno Keppens, and J. Pepijn Veefkind

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-2167', Juseon Bak, 19 Jul 2025

Attached

Citation: https://doi.org/10.5194/egusphere-2025-2167-RC1
- AC1: 'Reply on RC1', Serena Di Pede, 07 Nov 2025
  
  Please find the reply answers in the attached pdf document.
  
  Citation: https://doi.org/10.5194/egusphere-2025-2167-AC1
RC2:
'Comment on egusphere-2025-2167', Glen Jaross, 07 Aug 2025

In general, I find this manuscript version improved over the initial submission. The authors have done a better job of organizing results to make clear when corrections are and are not applied. More explicit statements for each figure would still be appreciated. It is clear that the new instrument characterization described in this paper is improving the accuracy of the radiance data (thereby reducing the magnitude of soft calibration corrections), but some of the details regarding how those improvements were achieved is lacking. It is only by providing such details that readers can evaluate the quality of the characterizations and learn something about instrument performance.
Section 2.2, Lines 135-138

This text describes the contents of Figure 2, which presents a compelling case that the Mg line signals have increased over time relative to background signals. Unfortunately, the reader has no idea from this figure what the time scales are, since the paper provides no assignment of dates for S5P orbit numbers. Two common reasons these Fraunhofer line changes occur is solar activity and improper correction for additive signal errors. The most likely additive errors are detector dark current and spectral stray light. All three phenomena are valid explanations for why the Mg line depths shown in Fig. 2 are decreasing. The authors state that the Fig. 2 results are independent of solar activity effects, but offer no details supporting this statement. Was a correction applied, and if so what was it? They do not discuss their background signal corrections, which must also increase as the instrument ages. These are glaring omissions if they expect the reader to accept the most surprising conclusion, that internally-scattered stray light is increasing within TropOMI. There are few plausible mechanisms for postlaunch increases in spectrometer scattering (primarily caused by the grating), so the authors need a convincing argument why the least likely of the 3 explanations is in fact the actual cause of the observed signal changes. One convincing metric would be to compare the Mg II core-to-wing ratios from solar irradiance and Earth radiance spectra at different times in the mission. In the absence of additive errors these two ratios should remain in lock step with each other. If, however, spectral stray light is increasing, the effect on Earth radiances should be much greater than on solar irradiances.
Section 2.2.1, Line 153

The statement that the SL correction algorithm is a 2D correction that only addresses in-band stray light is confusing. I suspect the authors mean the correction address both spatial and spectral stray light, but the latter is limited to only photons from within the same band. If so, a clarification of this point would be helpful.
Section 2.2.1, Lines 179-189

The authors should provide a clearer explanation of how the SL convolution kernels are adjusted. What criteria were used to assess the correct spectral and spatial distributions? Scattering occurring after the entrance slit typically has no preferential spatial or spectral direction. The 2D scattering PSF is usually symmetric. Therefore, the large difference in the two orthogonal cross sections of that PSF (shown in Fig. 3) is rather surprising and the authors are encouraged to provide more detail about why they feel the shapes should behave so differently. I presume that telescope stray light (i.e. pre-slit scattering) has been excluded from the plots in Fig. 3a. Please state so explicitly.
Section 2.4

The authors mention the introduction of time-varying SL correction to account for the increasing Mg II signals and the SL row signals, but they provide no details about how this is implemented. Are the kernel shapes altered in time? If so, how? Are the spatial and spectral components of the kernel locked relative to each other or allowed to vary independently? Whatever the approach, it will be helpful if the authors can demonstrate the effect of these dynamic corrections on the metrics shown in Figures 2 and 4. Figure 10 does indicate the effect on RTM residuals of these instrument corrections, but it does not address the effect on irradiance or stray light rows.
Section 4.3

Regarding the observed residuals (as represented by soft calibration corrections) presented in Figures 7 & 8 the authors do not discuss whether or not a solar activity correction has been applied. The increase seen in Figure 7a is consistent with the activity increase over the mission timeline. Figure 8 also appears to be consistent with the increase. An accurate solar activity correction must be applied prior to residual analysis, therefore the authors should provide details about any correction that was applied. What data was it derived from? What is the magnitude of the changes in time at key band 1 wavelengths?

Citation: https://doi.org/10.5194/egusphere-2025-2167-RC2
- AC2: 'Reply on RC2', Serena Di Pede, 07 Nov 2025
  
  Please find the reply answers in the attached pdf document.
  
  Citation: https://doi.org/10.5194/egusphere-2025-2167-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-2167', Juseon Bak, 19 Jul 2025

Attached

Citation: https://doi.org/10.5194/egusphere-2025-2167-RC1
- AC1: 'Reply on RC1', Serena Di Pede, 07 Nov 2025
  
  Please find the reply answers in the attached pdf document.
  
  Citation: https://doi.org/10.5194/egusphere-2025-2167-AC1
RC2:
'Comment on egusphere-2025-2167', Glen Jaross, 07 Aug 2025

In general, I find this manuscript version improved over the initial submission. The authors have done a better job of organizing results to make clear when corrections are and are not applied. More explicit statements for each figure would still be appreciated. It is clear that the new instrument characterization described in this paper is improving the accuracy of the radiance data (thereby reducing the magnitude of soft calibration corrections), but some of the details regarding how those improvements were achieved is lacking. It is only by providing such details that readers can evaluate the quality of the characterizations and learn something about instrument performance.
Section 2.2, Lines 135-138

This text describes the contents of Figure 2, which presents a compelling case that the Mg line signals have increased over time relative to background signals. Unfortunately, the reader has no idea from this figure what the time scales are, since the paper provides no assignment of dates for S5P orbit numbers. Two common reasons these Fraunhofer line changes occur is solar activity and improper correction for additive signal errors. The most likely additive errors are detector dark current and spectral stray light. All three phenomena are valid explanations for why the Mg line depths shown in Fig. 2 are decreasing. The authors state that the Fig. 2 results are independent of solar activity effects, but offer no details supporting this statement. Was a correction applied, and if so what was it? They do not discuss their background signal corrections, which must also increase as the instrument ages. These are glaring omissions if they expect the reader to accept the most surprising conclusion, that internally-scattered stray light is increasing within TropOMI. There are few plausible mechanisms for postlaunch increases in spectrometer scattering (primarily caused by the grating), so the authors need a convincing argument why the least likely of the 3 explanations is in fact the actual cause of the observed signal changes. One convincing metric would be to compare the Mg II core-to-wing ratios from solar irradiance and Earth radiance spectra at different times in the mission. In the absence of additive errors these two ratios should remain in lock step with each other. If, however, spectral stray light is increasing, the effect on Earth radiances should be much greater than on solar irradiances.
Section 2.2.1, Line 153

The statement that the SL correction algorithm is a 2D correction that only addresses in-band stray light is confusing. I suspect the authors mean the correction address both spatial and spectral stray light, but the latter is limited to only photons from within the same band. If so, a clarification of this point would be helpful.
Section 2.2.1, Lines 179-189

The authors should provide a clearer explanation of how the SL convolution kernels are adjusted. What criteria were used to assess the correct spectral and spatial distributions? Scattering occurring after the entrance slit typically has no preferential spatial or spectral direction. The 2D scattering PSF is usually symmetric. Therefore, the large difference in the two orthogonal cross sections of that PSF (shown in Fig. 3) is rather surprising and the authors are encouraged to provide more detail about why they feel the shapes should behave so differently. I presume that telescope stray light (i.e. pre-slit scattering) has been excluded from the plots in Fig. 3a. Please state so explicitly.
Section 2.4

The authors mention the introduction of time-varying SL correction to account for the increasing Mg II signals and the SL row signals, but they provide no details about how this is implemented. Are the kernel shapes altered in time? If so, how? Are the spatial and spectral components of the kernel locked relative to each other or allowed to vary independently? Whatever the approach, it will be helpful if the authors can demonstrate the effect of these dynamic corrections on the metrics shown in Figures 2 and 4. Figure 10 does indicate the effect on RTM residuals of these instrument corrections, but it does not address the effect on irradiance or stray light rows.
Section 4.3

Regarding the observed residuals (as represented by soft calibration corrections) presented in Figures 7 & 8 the authors do not discuss whether or not a solar activity correction has been applied. The increase seen in Figure 7a is consistent with the activity increase over the mission timeline. Figure 8 also appears to be consistent with the increase. An accurate solar activity correction must be applied prior to residual analysis, therefore the authors should provide details about any correction that was applied. What data was it derived from? What is the magnitude of the changes in time at key band 1 wavelengths?

Citation: https://doi.org/10.5194/egusphere-2025-2167-RC2
- AC2: 'Reply on RC2', Serena Di Pede, 07 Nov 2025
  
  Please find the reply answers in the attached pdf document.
  
  Citation: https://doi.org/10.5194/egusphere-2025-2167-AC2

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload

AR by Serena Di Pede on behalf of the Authors (07 Nov 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (10 Nov 2025) by Mark Weber

RR by Juseon Bak (21 Nov 2025)

RR by Glen Jaross (25 Nov 2025)

Suggestions for revision or reasons for rejection

The authors have improved their manuscript since the previous submission and some of the open questions have been addressed. But the discussion in several of the sections remain confusing. I strongly encourage the authors to review the manuscript again for clarity to ensure that important points are stated in simple language at the appropriate locations in the text. In several cases it only became clear what the authors meant when I read discussions later in the manuscript. I have identified a few of these instances (see below), but my review in this respect is not complete. I feel that a few sentences early in this paper outlining the analysis approach will help the reader to connect the content in the various sections.

Some of my comments about the earlier version of this paper related to conclusions about the stray light characteristics that I felt were inadequately substantiated. In this revised version it seems as though the authors have the evidence at their fingertips to demonstrate they are accurately describing the internally scattered stray light characteristics of TropOMI. But actual evidence in this latest version of the manuscript is still lacking. The observed MgII index and the stray light region contents are two independent pieces of information about internally scattered stray light. The instrument parameter that connects the two is the stray light kernel. There are many potential stray light kernels that could equally explain one or the other of the observed phenomena. The authors will have a persuasive argument regarding their chosen SL kernel changes if they can demonstrate it explains both the MgII index and stray light row changes simultaneously. Perhaps the authors believe they have accomplished this, but I do not see the clear "2+2=4" arguments in the text. It may be that only minor adjustments are needed to achieve this objective.

There should also be a discussion of the problems remaining in this new product. If the authors believe the resulting Level 1 product is not suitable for ozone trend analysis, they should state so and explain why. Don't leave it to the more careful readers to figure this out for themselves.

Line 125-129
The flow of the discussion here is awkward. I find myself reading a rereading the sentences trying understand the authors' points. A clearer approach would be to first discuss all the potential explanations for the behavior of the MgII line depth, including solar irradiance change, then eliminate the ones that are not plausible. Walk the reader through the logic rather than hiding the key points in clauses at the end of sentences.

Line 143
What are the authors intending to say in this sentence? Addressed by whom or by what? The correction algorithm? This paper? The detector? It is unclear what this sentence means in the context of the preceding discussion.

Line 165
I recommend that the authors find a term other than "far-field" to describe Band 1 stray light originating from Band 2. Far-field or out-of-field refers to the field angle, which is a spatial dimension. Its use in describing the spectral dimension of stray light is confusing. Please use "out-of-band stray light" or more generically "spectral stray light" to describe contributions in the spectral dimension (also in Line 330).

Lines 170-175
The authors discuss the motivation for altering the stray light kernels: non-zero signal content in the stray light region after SL correction, and over-correction in Band 1. The authors provide detailed explanations for the stray light kernel assessment in Appendix B, but only for the spatial kernel adjustment. The stray light region contents are far more sensitive to the shape of the spatial kernel than to the shape of the spectral kernel, and therefore the latter cannot be tuned on the basis of the stray light region data. Since spectral stray light should be the main focus of this paper (it is the primary cause of their ozone profile retrieval errors), it would be best if the authors clearly and explicitly present the methodology for modifying the spectral axis shape of the kernel.

Section 2.2
The authors fail to describe how the dynamic SL correction is actually implemented. This is not an irrelevant detail because there are several possible approaches and not all will equally explain the observed measurements. Is the time-dependent behavior based on the MgII lines or is it based on the stray light region contents? Is the kernel modified by broadening its width or are the tails merely increased by adding a uniform background to the kernel? Are the spectral and spatial kernels adjusted identically or independently. These choices will significantly affect the residual signals.

Section 2.3
The authors explain that there are signal errors remaining even after the standard signal corrections. They describe the correction as a CKD image, which requires a bit more explanation for readers (or eliminate it if it provides no useful information). It is difficult to understand from the discussion exactly what artifacts are being corrected; how are they identified and how are they corrected. What is the magnitude of the correction? It is only in the discussion surrounding Figure 9 later in the paper that the reader discovers these additional signal corrections have little effect on the results. The authors should say so in this section. As currently written, the reader is left wondering what these errors are and the role they play in the observed TropOMI radiometric behavior.

Lines 201-204
The before/after comparison of the MgII index and Ca K line index shown in Figure A2 suggests the post-correction signal variation at 280 nm may be close to true solar variation, but it is hardly convincing evidence. It would be better if the authors could directly compare the post-correction MgII index observed by TropOMI with a predicted index (adjusted for the TropOMI bandwidth) based on an external source . Furthermore, this evidence and its discussion should not be relegated to an appendix. In my opinion, it is central to the stray light discussion and the authors' assertion that TropOMI stray light characteristics are changing in orbit.

Section 3
In this section the authors describe an approach to radiometric corrections that is rather difficult to follow. It lacks a high-level discussion of the authors' motivation for choosing this soft calibration approach. For example, it appears that the soft calibration of TropOMI is based on ozone climatology, not just initially but also throughout the mission. I presume this means the authors have given up on producing radiances suitable for trend-quality ozone retrievals. If this is the case, the authors should say so clearly and unequivocally here and in the abstract. If it is not the case, the authors need a clearer discussion in this section to explain how radiance trends are preserved.

The soft calibration approach also addresses an apparent non-linear response of the instrument. Is this an existing operational correction that you are merely updating to be more accurate, or is this an entirely new correction? Though this may have been previously described in another publication, these unusual corrections need some high-level description and justification. Figures 7 and D2 indicate there is a residual non-linearity in the instrument system. What is the cause of this non-linearity? Detector? Stray light overcorrection? Incorrect wavelength registration? Something else? How this non-linearity is addressed depends a lot on its cause. For example, a detector non-linearity will not have a wavelength dependence, nor does it typically have much time-dependence. Stray light errors are not addressed well by broad addition or subtraction of signal because they depend on neighboring pixel signals. Indeed, a comparison of Figures 9 and 10 suggests that some of the non-linearity was caused by stray light, but much of the non-linearity remains between versions. Even if the authors do not know the exact cause, they should be able to speculate how these errors might arise. The statements by the authors in lines 309-312 that such discussion is outside the scope of this study do not absolve the authors of their responsibility to convince the readers they are addressing the data problems in an appropriate manner.

Section 3.4 and Figure 8
It is clear, upon reading Section 4, that the soft calibration presented here applies to the current operational processing rather than the proposed future operation processing. This point should be stated more clearly. Perhaps the authors should refer to the actual product version numbers rather than "operational" and "updated" to indicate old and new.

Lines 314-317
This is a confusing paragraph. Exactly which corrections were applied in the reprocessing? Based on the subsequent text in this section and the contents of Figure 9, it seems that the authors are trying to say that they are recomputing the soft cal. correction for different combinations of instrument corrections applied in the L1B processing. If this is what the authors mean, just state so in plain and simple language. What does the sentence "The soft calibration procedure is instead kept the same ..." ? Instead of what?

Lines 330
The authors refer to a spectral cut off of the stray light convolution kernel. If such a cutoff was described in Section 2.2.1 it was not done so in a clear manner that allows the reader to identify what feature of the kernel the authors are referring to here. Are the authors saying the narrower kernel reduces the contributions to Band 1 from Band 2? If so, please say that instead of calling it a cut off.

Lines 339
Please identify the quantity being discussed. The time difference between two orbits is a constant and cannot become smaller, so the authors must be referring to something else. Correction magnitude?

Line 370
The sentence beginning "We do not observe ..." is awkward. I do not understand what the authors are trying to say. Perhaps removing the word "instead" will help. I've noticed several places throughout the manuscript where this word has been unnecessarily introduced.

Lines 372-373
The authors here conclude on the basis of Figures 12b and 12d that there is a reduction in anomalies. This point is not at all clear from the figures. By some criteria it could be argued the new version actually looks worse. I recommend revising the figures to more clearly support your conclusion. Or perhaps the authors just need to revise their tropospheric ozone conclusions.

Lines 385-387
Please make it clear that this statement refers to the current operational product.

Grammatical
Line 127: "a part for the spectral region"
Line 134: "part of to the instrument"
Line 238: "and the ISRF also updated"
Line 264: "approach as described in (?)"
Line 331: "between the orbits is reduced of around"
Line 350: "slightly increases of around 0.2% .... it decreases of 1-2%" See also Line 365, 394.
Line 374: "as it can be seen from"
Line 375: "they decrease of few percents"
Line 388: "updated with adjustments regarding"

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ED: Reconsider after major revisions (01 Dec 2025) by Mark Weber

AR by Serena Di Pede on behalf of the Authors (27 Jan 2026) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (28 Jan 2026) by Mark Weber

RR by Glen Jaross (03 Feb 2026)

Suggestions for revision or reasons for rejection

I thank the authors for taking the time to rewrite significant portions of the text. It has made a difference. I find the flow of the paper easier to follow than in the previous version, with more coherency between sections. The authors have added more discussion of the motivations behind the steps they've taken, which makes other unchanged components of manuscript easier to understand. There are several small issues remaining (noted below), but these do not detract from what is now a well-constructed paper.

Section 2.3, 1st paragraph
The logic in this paragraph is not clear. The paragraph starts by saying that the SL kernels are too small (too narrow) based on the observation of the stray light row signal increase compared to its calculated increase. The second sentence seems to say that if the kernel was sufficiently large the SL row contents would be much lower than observed. Do the authors instead mean the SL row contents would be much larger than observed? Or is the problem with the use of the word "would" in the second sentence? Perhaps it should be "does".

The description in Section 2.3 of how the SL kernel and SL row information is combined is reasonably clear, though perhaps more complicated than it needs to be. To say that the SL kernel remains static is not really true since the dynamic SL correction effectively increases and decreases the kernel tails in a way that explains the SL row contents. Even though this is not how the correction is implemented in the code, it may help to describe the new correction as a time varying kernel where only the tails are allowed to vary.

Section 2.4
It will help to add a sentence that provides the motivation behind explicitly adjusting the SL kernel. The Section 2.3 discussion gives the impression that the dynamic SL correction compensates for errors in the SL kernel. Why then is it important to get the SL kernel as close to correct as possible? The answer becomes clear in the Section 4 evaluations, but it would help the reader if those justifications were prefaced in this section.

Section 3.2
The authors describe their use of CAMS to seed their RTM calculations, and state that the CAMS total ozone is scaled to that of TropOMI and ozone profiles are scaled to those of MLS. The authors do not indicate if this profile adjustment is a one-time scaling or the rescaling occurs independently for each CAMS-MLS matchup. The former amounts to a time-independent soft calibration adjustment to MLS ozone, while the latter would tie TropOMI long-term ozone profile changes to those of MLS. This distinction, while not very important when assessing L1 calibration, is very important in understanding the independence of the L2_O3_PR product. Since this paper is not about the L2 profile product, I leave it to the authors to decide whether to clarify this issue or leave it ambiguous.

Section 4, Line 405
The text references Figure 11l, but there is no such figure. Is this a typo?

Section 5, Lines 448-450
The authors reference Figure 16 when stating that the L1 calibration improvements are the main cause of across-track reduction in tropospheric ozone anomalies. No doubt the observed changes were caused by calibration changes, but evidence from Figures 16e and 16f that anomalies have decreased is scant. There is certainly some improvement on the western side of the swath, but it is difficult to see the other improvements the authors describe. Likewise, a reduction in importance of the soft calibration to across-track anomalies, as claimed by the authors, would suggest similarity between Figures 16f and 16h. While the two share some features, they are not obviously closer than the similarity between Figures 16e and 16g. The authors note the smaller latitude dependence of the anomalies in v3.0. This does not necessarily represent an improvement since the v3.0 anomaly is now more recognizable as an across-track bias rather than as geophysical in origin. I find the evidence in this figure rather limited compared to the conclusions the authors draw from it, and would prefer their statements were less expansive in this regard.

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ED: Publish subject to technical corrections (16 Feb 2026) by Mark Weber

AR by Serena Di Pede on behalf of the Authors (24 Feb 2026) Author's response Manuscript

Journal article(s) based on this preprint

17 Mar 2026

Characterization and improvements of the UV radiometric calibration for the TROPOMI operational ozone profile retrieval algorithm

Serena Di Pede, Erwin Loots, Antje Ludewig, Emiel van der Plas, Edward van Amelrooy, Mirna van Hoek, Maarten Sneep, Mark ter Linden, Arno Keppens, and J. Pepijn Veefkind

Atmos. Meas. Tech., 19, 1875–1899, https://doi.org/10.5194/amt-19-1875-2026,https://doi.org/10.5194/amt-19-1875-2026, 2026

Short summary

Serena Di Pede, Erwin Loots, Emiel van der Plas, Maarten Sneep, Edward van Amelrooy, Mirna van Hoek, Mark ter Linden, Antje Ludewig, Arno Keppens, and J. Pepijn Veefkind

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The Sentinel-5P is a satellite operated by the European Space Agency, carrying the TROPOspheric Monitoring Instrument (TROPOMI). This mission also produces atmospheric ozone profile data using measurements in the ultra-violet spectrum. Absolute spectra calibration is necessary to produce high quality ozone profile data. Soft-calibration is a technique used to obtain accurate input spectra for ozone profile retrievals. The new soft-calibration shows reduced size and less temporal/spectral bias.


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