the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 27 Mar 2025
DNS (v1.0): An open source ray-tracing tool for space geodetic techniques
Abstract. We have developed an open source ray-tracing tool for space geodetic techniques. The software uses the geometric optics approximation to calculate the signal travel time delay induced by the atmosphere between two given points. The software is written in Fortran and uses OpenMP to speed up computation. The input to the ray-tracing tool are 3D pressure-, temperature- and humidity fields. The Earths magnetic- and electron density field are optional. For the neutral atmosphere (troposphere) the software accepts the NetCDF files from the atmospheric reanalysis ERA5 and the mesoscale model WRF. For the ionosphere the software accepts electron density fields derived from IRI and Ne-quick. We review the current status of the software and test its performance. For example, the one-to-one comparison with the open source software RADIATE shows the high speed and precision of our ray-tracing tool. We also show how our tool can be used to study higher order ionospheric effects (L-band frequencies). The two outstanding features of the ray-tracing tool compared to previous model developments, i.e., the ability to handle both the troposphere and the ionosphere and do so efficiently, make it perfectly suited for geoscientific applications.
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Status: open (until 22 May 2025)
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CEC1: 'Comment on gmd-2024-237', Juan Antonio Añel, 08 Apr 2025
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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 EditorCitation: https://doi.org/10.5194/gmd-2024-237-CEC1 -
AC1: 'Reply on CEC1', Florian Zus, 09 Apr 2025
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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
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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
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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
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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
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CEC3: 'Reply on AC2', Juan Antonio Añel, 14 Apr 2025
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AC2: 'Reply on CEC2', Florian Zus, 10 Apr 2025
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CEC2: 'Reply on AC1', Juan Antonio Añel, 09 Apr 2025
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AC1: 'Reply on CEC1', Florian Zus, 09 Apr 2025
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RC1: 'Comment on gmd-2024-237', Anonymous Referee #1, 17 Apr 2025
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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 -
AC3: 'Comment on gmd-2024-237', Florian Zus, 17 Apr 2025
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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
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