DNS (v1.0): an open-source ray-tracing tool for  space geodetic techniques

Zus, Florian; Balidakis, Kyriakos; Dogan, Ali Hasan; Thundathil, Rohith; Dick, Galina; Wickert, Jens

doi:https://doi.org/10.5194/gmd-18-4951-2025

Articles | Volume 18, issue 15

https://doi.org/10.5194/gmd-18-4951-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/gmd-18-4951-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 18, issue 15

Development and technical paper

|

13 Aug 2025

Development and technical paper |

| 13 Aug 2025

DNS (v1.0): an open-source ray-tracing tool for space geodetic techniques

Florian Zus, Kyriakos Balidakis, Ali Hasan Dogan, Rohith Thundathil, Galina Dick, and Jens Wickert

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Final revised paper (published on 13 Aug 2025)
Preprint (discussion started on 27 Mar 2025)

Interactive discussion

Status: closed

CEC1:
'Comment on gmd-2024-237', Juan Antonio Añel, 08 Apr 2025

Dear authors,
Unfortunately, after checking your manuscript, it has come to our attention that it does not comply with our "Code and Data Policy".

https://www.geoscientific-model-development.net/policies/code_and_data_policy.html

The RADIATE code is archived on GitHub. However, GitHub is not a suitable repository for scientific publication. GitHub itself instructs authors to use other long-term archival and publishing alternatives, such as Zenodo. Therefore, the current situation with your manuscript is irregular. Please, publish the RADIATE code in one of the appropriate repositories (you can do it, as it is under the GPLv3 license) and reply to this comment with the relevant information (link and a permanent identifier for it (e.g. DOI)) as soon as possible, as we can not accept manuscripts in Discussions that do not comply with our policy.
Please, note that if you do not fix this problem, we will have to reject your manuscript for publication in our journal. Moreover, you must include a modified 'Code and Data Availability' section in a potentially reviewed manuscript, containing the DOI of the new repositories.
Also, I would like to take advantage of this comment to make a small note as a reviewer. Given that your model is developed in Fortran, have you checked the code quality before releasing it? If not it could greatly benefit of checking potential issue improvements with a tool such as FortranAnalyser (https://fortrananalyser.ephyslab.uvigo.es/) and reporting here on the quality of the code.
Juan A. Añel

Geosci. Model Dev. Executive Editor

Citation: https://doi.org/10.5194/gmd-2024-237-CEC1
- AC1:
  'Reply on CEC1', Florian Zus, 09 Apr 2025
  
  As you requested, we published the RADIATE code in one of the appropriate repositories (Zenodo). The code is now available via Zus, F. (2025). RADIATE ray-tracing code. Zenodo. https://doi.org/10.5281/zenodo.15180888. We will include a modified 'Code and Data Availability' section in a potentially reviewed manuscript, containing the DOI of the new repositories. As suggested, we utilized the FortranAnalyser to check for improvements. The final/overall score is 3.687. We thank you for this hint, and we are going to utilize this tool to improve the code, in particular the score for the metric comments.
  
  Citation: https://doi.org/10.5194/gmd-2024-237-AC1
  - CEC2: 'Reply on AC1', Juan Antonio Añel, 09 Apr 2025
    
    Dear authors,
    Many thanks for addressing the mentioned issue so quickly. However, an issue remains outstanding. To run your software it is necessary to download data from a server (https://vmf.geo.tuwien.ac.at) which does not comply with our requirements for data publication. Therefore, to assure the replicability of the work that you present, it is necessary that you store the necessary files to be dowloaded in one of the permanent repositories listed in our policy, and reply to this comment with its link and permanent identifier. Also, it would be good that in the instructions to run the model in Zenodo you change the mentioned server to the new repositories.
    Please, address these issues.
    Juan A. Añel
    Geosci. Model Dev. Executive Editor
    
    Citation: https://doi.org/10.5194/gmd-2024-237-CEC2
    
    AC2: 'Reply on CEC2', Florian Zus, 10 Apr 2025
    
    As suggested, to assure the replicability of the work that we present, we store the necessary weather model input files in one of the permanent repositories (Zenodo). It is now available at Zus, F. (2025). Numerical(Space-)Weather Model dataset for the ray-tracing tool DNS [Data set]. Zenodo. https://doi.org/10.5281/zenodo.15187660. We updated the instructions of the other two models stored in the permanent repository.
    
    Citation: https://doi.org/10.5194/gmd-2024-237-AC2
    
    CEC3: 'Reply on AC2', Juan Antonio Añel, 14 Apr 2025
    
    Dear authors,
    Many thanks for your quick reply. We can consider now the current version of your manuscript in compliance with the policy of the journal.
    Juan A. Añel
    Geosci. Model Dev. Executive Editor
    
    Citation: https://doi.org/10.5194/gmd-2024-237-CEC3
RC1:
'Comment on gmd-2024-237', Anonymous Referee #1, 17 Apr 2025

The authors Florian Zus et al. introduce an open source ray-tracing tool for space geodetic techniques, named DNS (v1.0). This tool is very efficient in calculating ray-traced delays at optical and microwave frequencies in the neutral atmosphere and ionosphere, applying various numerical data sets such as operational or re-analysis datasets of the ECMWF and Nequick2.
With its speed (at least an order of magnitude faster than existing packages), it provides users with the possibility to improve parameterized models, such as mapping functions. Congratulations and thanks for providing this tool to the community.

Minor comments:
l122: Dealy -> Delay
l144: \theta is not used in equation (\varphi)
l179: angel -> angle
l319: hypothesis
l336: utilized
Figures 4 and 5: Should it read d_h^z instead of d_n^z ?
Figure 6 is hardly readable

Citation: https://doi.org/10.5194/gmd-2024-237-RC1
- AC4: 'Reply on RC1', Florian Zus, 26 May 2025
  
  Please find attached our point to point response.
  
  Citation: https://doi.org/10.5194/gmd-2024-237-AC4
AC3: 'Comment on gmd-2024-237', Florian Zus, 17 Apr 2025

After re-reading of the manuscript, we discovered a few minor issues:
* Page 8, line 235: We forgot to mention that there is another option for the ionosphere (#4):
(4) Data from the Global Total Electron Content (GloTEC) model. The NetCDF files are available from the NOAA Space Weather Prediction Center (https://services.swpc.noaa.gov/products/ glotec/). The GloTEC is a data-assimilative model (Chou et al., 2023). Therefore, model results at the locations where observations are ingested are most trustworthy. Where there are no observations, the model tends to relax towards the background (IRI).
* Page 19, line 440: ‘…We consider the same 2592 grid point coordinates with global coverage and a single epoch (15 March 2013, 12UTC) which is regarded representative for a period of high solar activity…’. The epoch is wrong. It must be 15 March 2015, 12 UTC.
* Page 19, line 450: The figure 8 is wrong. It is for the year 2013 and should be for the year 2015. The caption is correct. The correct figure will be included in a possible revised version of the manuscript.
* Finally, we would like to mention that the software works not only for links between ground based stations and satellites (or quasars) but also for links between LEO- and MEO satellites. This will broaden the use of the ray-tracing tool. For example, the ray-tracing tool can be used to study first- and higher order corrections in LEO precise orbit determination. We will provide this information in the conclusion/outlook section of the potentially revised version of the manuscript.

Citation: https://doi.org/10.5194/gmd-2024-237-AC3
RC2:
'Comment on gmd-2024-237', Anonymous Referee #2, 27 Apr 2025

see attachment

Citation: https://doi.org/10.5194/gmd-2024-237-RC2
- AC5: 'Reply on RC2', Florian Zus, 26 May 2025
  
  Please find attached our point-to-point response.
  
  Citation: https://doi.org/10.5194/gmd-2024-237-AC5

Peer review completion

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

AR by Florian Zus on behalf of the Authors (05 Jun 2025) Author's response Author's tracked changes Manuscript

ED: Publish as is (05 Jun 2025) by Tatiana Egorova

AR by Florian Zus on behalf of the Authors (06 Jun 2025)

Short summary

Atmospheric signal propagation effects are one of the largest error sources in the analysis of space geodetic techniques. Inaccuracies in the modelling map into errors in positioning, navigation and timing. We describe the open-source ray-tracing tool DNS and show the two outstanding features of this tool compared to previous model developments: it can handle both the troposphere and the ionosphere, and it does so efficiently. This makes the tool perfectly suited for geoscientific applications.