Sustainability

My research in aviation sustainability is multifaceted, making significant contributions to the field. I use large-scale open data for precise emission estimations, optimizing flight operations to minimize emissions. I also focus on identifying and mitigating contrails, an often-overlooked aspect of aviation's environmental impact.

Highlights

Contrail, or Not Contrail: The Feasibility of Climate-Optimal Routing

This 2025 preprint examines the practical challenges of contrail-aware routing using OpenSky trajectories, OpenAP, and trajectory optimization. It investigates fuel–contrail trade-offs, uncertainty in weather forecasts, and the effects of rerouting on airspace capacity, showing why operational and policy constraints matter alongside the potential climate benefits.

Global Aviation Emissions with OpenSky Data

In this study, we perform an analysis of all captured global flights for one year (2018), with trajectories down-sampled to one point per 30 seconds. These high-resolution trajectories are used to construct carbon emission estimates, combined with the OpenAP model. We concluded that reduced models are sufficient for large-scale aggregated emissions statistics, but precise models remain more accurate and provide better assessments to measure the impact of particular flight procedures.

Contrail-Net: Neural networks models for contrail detection and segmentation

An open-source contrail segmentation model in PyTorch. It uses augmented transfer learning, applying image augmentations to a pre-trained ResUNet so the model can be fine-tuned with only a handful of labelled satellite images. A new loss function, SR Loss, further improves detection by exploiting contrail information in Hough space.

Generation of climate optimal trajectories with OpenAP.TOP

An open-source flight trajectory optimizer based on direct collocation. It supports conventional fuel and cost-index objectives as well as climate-based objectives using global warming or temperature potentials.

Related publications

Assessing Climate Impact of Contrails: Insights from Japan’s High-Density Airspace and Meteorological Conditions
Conference 2025
Sekine, Katsuhiro ; Hasegawa, Tomoki ; Sun, Junzi ; and Itoh, Eri
In Proceedings of the 16th USA-Europe Seminar on Air Traffic Management Research and Development (ATM 2025)
Copy Sekine, K., Hasegawa, T., Sun, J., & Itoh, E. (2025). Assessing Climate Impact of Contrails: Insights from Japan’s High-Density Airspace and Meteorological Conditions. Proceedings of the 16th USA-Europe Seminar on Air Traffic Management Research and Development (ATM 2025), 116–126.
Copy
@inproceedings{sekine2025assessing, title = {Assessing Climate Impact of Contrails: Insights from Japan's High-Density Airspace and Meteorological Conditions}, author = {Sekine, Katsuhiro and Hasegawa, Tomoki and Sun, Junzi and Itoh, Eri}, booktitle = {Proceedings of the 16th USA-Europe Seminar on Air Traffic Management Research and Development (ATM 2025)}, pages = {116--126}, year = {2025}, month = jun, publisher = {EUROCONTROL}, link = {https://research.tudelft.nl/files/284295006/sekine202506ATRDS_paper_final.pdf}, tag = {sus} }
Dataset for the "contrail, or not contrail" paper
Dataset 2025 DOI: 10.6084/m9.figshare.29400650.v2
Sun, Junzi ; and Olive, Xavier
figshare
Copy Sun, J., & Olive, X. (2025). Dataset for the "contrail, or not contrail" paper [Dataset]. figshare. https://doi.org/10.6084/m9.figshare.29400650.v2
Copy
@misc{sun2025contraildataset, title = {Dataset for the "contrail, or not contrail" paper}, author = {Sun, Junzi and Olive, Xavier}, publisher = {figshare}, year = {2025}, month = jun, doi = {10.6084/m9.figshare.29400650.v2}, link = {https://doi.org/10.6084/m9.figshare.29400650.v2}, type = {Dataset}, tag = {sus} }
Contrail, or not contrail, that is the question: the "feasibility" of climate-optimal routing
preprint 2025
Sun, Junzi ; and Olive, Xavier
Copy Sun, J., & Olive, X. (2025). Contrail, or not contrail, that is the question: the "feasibility" of climate-optimal routing.
Copy
@preprint{sun2025contrail, title = {Contrail, or not contrail, that is the question: the "feasibility" of climate-optimal routing}, author = {Sun, Junzi and Olive, Xavier}, year = {2025}, eprint = {2504.13907}, archiveprefix = {arXiv}, primaryclass = {physics.ao-ph}, link = {https://arxiv.org/abs/2504.13907}, tag = {sus} }
Few-Shot Contrail Segmentation in Remote Sensing Imagery With Loss Function in Hough Space
Journal 2025 DOI: 10.1109/JSTARS.2025.3525576
Sun, Junzi ; and Roosenbrand, Esther
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
Copy Sun, J., & Roosenbrand, E. (2025). Few-Shot Contrail Segmentation in Remote Sensing Imagery With Loss Function in Hough Space. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. https://doi.org/10.1109/JSTARS.2025.3525576
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@article{sun2025few, title = {Few-Shot Contrail Segmentation in Remote Sensing Imagery With Loss Function in Hough Space}, author = {Sun, Junzi and Roosenbrand, Esther}, journal = {IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing}, year = {2025}, publisher = {IEEE}, doi = {10.1109/JSTARS.2025.3525576}, link = {https://doi.org/10.1109/JSTARS.2025.3525576}, tag = {ai, sus} }
Quantifying the Efficacy of Weather Forecasting Data for Flight Contrail Optimization
Conference 2024
Roosenbrand, Esther ; Sun, Junzi ; and Hoekstra, Jacco
In Proceedings of the 14th SESAR Innovation Days, Rome, Italy
Copy Roosenbrand, E., Sun, J., & Hoekstra, J. (2024, November). Quantifying the Efficacy of Weather Forecasting Data for Flight Contrail Optimization. Proceedings of the 14th SESAR Innovation Days, Rome, Italy.
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@inproceedings{roosenbrand2024quantifying, title = {Quantifying the Efficacy of Weather Forecasting Data for Flight Contrail Optimization}, author = {Roosenbrand, Esther and Sun, Junzi and Hoekstra, Jacco}, booktitle = {Proceedings of the 14th SESAR Innovation Days, Rome, Italy}, year = {2024}, month = nov, link = {https://www.sesarju.eu/sites/default/files/documents/sid/2024/papers/SIDs_2024_paper_046%20final.pdf}, tag = {sus} }
OpenSky Report 2024: Analysis of Global Flight Contrail Formation and Mitigation Potential
Conference 2024
Sun, Junzi ; Olive, Xavier ; Roosenbrand, Esther ; Parzani, Céline ; and Strohmeier, Martin
In Proceedings of the 42th Digital Avionics Systems Conference
Copy Sun, J., Olive, X., Roosenbrand, E., Parzani, C., & Strohmeier, M. (2024, September). OpenSky Report 2024: Analysis of Global Flight Contrail Formation and Mitigation Potential. Proceedings of the 42th Digital Avionics Systems Conference.
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@inproceedings{sun2024openskyreport, title = {OpenSky Report 2024: Analysis of Global Flight Contrail Formation and Mitigation Potential}, author = {Sun, Junzi and Olive, Xavier and Roosenbrand, Esther and Parzani, C{\'e}line and Strohmeier, Martin}, booktitle = {Proceedings of the 42th Digital Avionics Systems Conference}, year = {2024}, month = sep, link = {https://www.researchgate.net/publication/382143324}, award = true, tag = {sus} }
Flight Optimization for Contrails and Emissions: A Large-Scale Trade-off Analysis Using Open Data and Models
Conference 2024
Roosenbrand, Esther ; Sun, Junzi ; and Hoekstra, Jacco
In Proceedings of the 11th International Conference for Research in Air Transportation
Copy Roosenbrand, E., Sun, J., & Hoekstra, J. (2024, July). Flight Optimization for Contrails and Emissions: A Large-Scale Trade-off Analysis Using Open Data and Models. Proceedings of the 11th International Conference for Research in Air Transportation.
Copy
@inproceedings{roosenbrand2024flight, title = {Flight Optimization for Contrails and Emissions: A Large-Scale Trade-off Analysis Using Open Data and Models}, author = {Roosenbrand, Esther and Sun, Junzi and Hoekstra, Jacco}, booktitle = {Proceedings of the 11th International Conference for Research in Air Transportation}, year = {2024}, month = jul, link = {https://resolver.tudelft.nl/uuid:4ff70cba-ac81-46c7-aa2c-f4d0405b394c}, tag = {sus} }
Contrail Formation and Mitigation in the Japanese Airspace: A Data-Driven Study
Conference 2024
Sun, Junzi ; Roosenbrand, Esther ; Nonaka, Yuki ; and Itoh, Eri
In Proceedings of the 11th International Conference for Research in Air Transportation
Copy Sun, J., Roosenbrand, E., Nonaka, Y., & Itoh, E. (2024, July). Contrail Formation and Mitigation in the Japanese Airspace: A Data-Driven Study. Proceedings of the 11th International Conference for Research in Air Transportation.
Copy
@inproceedings{sun2024contrailjapan, title = {Contrail Formation and Mitigation in the Japanese Airspace: A Data-Driven Study}, author = {Sun, Junzi and Roosenbrand, Esther and Nonaka, Yuki and Itoh, Eri}, booktitle = {Proceedings of the 11th International Conference for Research in Air Transportation}, year = {2024}, month = jul, link = {https://resolver.tudelft.nl/uuid:f3c74799-527d-4a07-b7c3-8647e66f61f2}, tag = {sus} }
Evaluating Transatlantic Flight Emissions and Inefficiencies Using Space-Based ADS-B Data
Conference 2023
Sun, Junzi ; Tassanbi, Aidana ; Obojski, Piotrek ; and Plantholt, Philip
In Proceedings of the 13th SESAR Innovation Days, Sevilla, Spain
Copy Sun, J., Tassanbi, A., Obojski, P., & Plantholt, P. (2023, December). Evaluating Transatlantic Flight Emissions and Inefficiencies Using Space-Based ADS-B Data. Proceedings of the 13th SESAR Innovation Days, Sevilla, Spain.
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@inproceedings{sun2023evaluating, title = {Evaluating Transatlantic Flight Emissions and Inefficiencies Using Space-Based ADS-B Data}, author = {Sun, Junzi and Tassanbi, Aidana and Obojski, Piotrek and Plantholt, Philip}, booktitle = {Proceedings of the 13th SESAR Innovation Days, Sevilla, Spain}, year = {2023}, month = dec, link = {https://doi.org/10.61009/SID.2023.1.41}, tag = {sus} }
Contrail Altitude Estimation Based on Shadows Detected in Landsat Imagery
Conference 2023
Roosenbrand, Esther ; Sun, Junzi ; and Hoesktra, Jacco
In Proceedings of the 13th SESAR Innovation Days, Sevilla, Spain
Copy Roosenbrand, E., Sun, J., & Hoesktra, J. (2023, December). Contrail Altitude Estimation Based on Shadows Detected in Landsat Imagery. Proceedings of the 13th SESAR Innovation Days, Sevilla, Spain.
Copy
@inproceedings{roosenbrand2023altitude, title = {Contrail Altitude Estimation Based on Shadows Detected in Landsat Imagery}, author = {Roosenbrand, Esther and Sun, Junzi and Hoesktra, Jacco}, booktitle = {Proceedings of the 13th SESAR Innovation Days, Sevilla, Spain}, year = {2023}, month = dec, link = {https://doi.org/10.61009/SID.2023.1.06}, tag = {sus, ai} }
Contrail minimization through altitude diversions: A feasibility study leveraging global data
Journal 2023 DOI: 10.1016/j.trip.2023.100953
Roosenbrand, Esther ; Sun, Junzi ; and Hoekstra, Jacco
Transportation Research Interdisciplinary Perspectives
Copy Roosenbrand, E., Sun, J., & Hoekstra, J. (2023). Contrail minimization through altitude diversions: A feasibility study leveraging global data. Transportation Research Interdisciplinary Perspectives, 22, 100953. https://doi.org/10.1016/j.trip.2023.100953
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@article{roosenbrand2023contrail, title = {Contrail minimization through altitude diversions: A feasibility study leveraging global data}, author = {Roosenbrand, Esther and Sun, Junzi and Hoekstra, Jacco}, journal = {Transportation Research Interdisciplinary Perspectives}, volume = {22}, pages = {100953}, year = {2023}, month = nov, publisher = {Elsevier}, doi = {10.1016/j.trip.2023.100953}, link = {https://doi.org/10.1016/j.trip.2023.100953}, tag = {sus} }
Open-source traffic and CO2 emission dataset for commercial aviation
Dataset 2023 DOI: 10.5281/zenodo.10143773
Salgas, Antoine ; Sun, Junzi ; Delbecq, Scott ; Planès, Thomas ; and Lafforgue, Gilles
Zenodo
Copy Salgas, A., Sun, J., Delbecq, S., Planès, T., & Lafforgue, G. (2023). Open-source traffic and CO2 emission dataset for commercial aviation [Dataset]. Zenodo. https://doi.org/10.5281/zenodo.10143773
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@misc{salgas2023trafficdataset, title = {Open-source traffic and CO2 emission dataset for commercial aviation}, author = {Salgas, Antoine and Sun, Junzi and Delbecq, Scott and Plan{\`e}s, Thomas and Lafforgue, Gilles}, publisher = {Zenodo}, year = {2023}, month = nov, doi = {10.5281/zenodo.10143773}, link = {https://doi.org/10.5281/zenodo.10143773}, type = {Dataset}, tag = {sus} }
Fast contrail estimation with OpenSky data
Conference 2023 DOI: 10.59490/joas.2023.7264
Sun, Junzi ; and Roosenbrand, Esther
In Proceedings of 10th OpenSky Symposium
Copy Sun, J., & Roosenbrand, E. (2023, November). Fast contrail estimation with OpenSky data. Proceedings of 10th OpenSky Symposium. https://doi.org/10.59490/joas.2023.7264
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@inproceedings{sun2023fast, title = {Fast contrail estimation with OpenSky data}, author = {Sun, Junzi and Roosenbrand, Esther}, booktitle = {Proceedings of 10th OpenSky Symposium}, publisher = {Journal of Open Aviation Science}, month = nov, year = {2023}, doi = {10.59490/joas.2023.7264}, link = {https://doi.org/10.59490/joas.2023.7264}, tag = {sus}, award = true }
Flight Contrail Segmentation via Augmented Transfer Learning with Novel SR Loss Function in Hough Space
preprint 2023
Sun, Junzi ; and Roosenbrand, Esther
Copy Sun, J., & Roosenbrand, E. (2023). Flight Contrail Segmentation via Augmented Transfer Learning with Novel SR Loss Function in Hough Space.
Copy
@preprint{sun2023flight, title = {Flight Contrail Segmentation via Augmented Transfer Learning with Novel SR Loss Function in Hough Space}, author = {Sun, Junzi and Roosenbrand, Esther}, year = {2023}, eprint = {2307.12032}, archiveprefix = {arXiv}, primaryclass = {cs.CV}, tag = {ai, sus} }
Environmental Footprint of Private and Business Jets
Conference 2022
Sun, Junzi ; Olive, Xavier ; and Strohmeier, Martin
In Proceedings of 10th OpenSky Symposium
Copy Sun, J., Olive, X., & Strohmeier, M. (2022, November). Environmental Footprint of Private and Business Jets. Proceedings of 10th OpenSky Symposium.
Copy
@inproceedings{sun2022environmental, title = {Environmental Footprint of Private and Business Jets}, author = {Sun, Junzi and Olive, Xavier and Strohmeier, Martin}, booktitle = {Proceedings of 10th OpenSky Symposium}, year = {2022}, month = nov, publisher = {MDPI}, link = {https://doi.org/10.3390/engproc2022028013}, tag = {sus} }
OpenSky Report 2022: Evaluating Aviation Emissions Using Crowdsourced Open Flight Data
Conference 2022
Sun, Junzi ; Basora, Luis ; Olive, Xavier ; Strohmeier, Martin ; Schäfer, Matthias ; Martinovic, Ivan ; and Lenders, Vincent
In Proceedings of the 40th Digital Avionics Systems Conference
Copy Sun, J., Basora, L., Olive, X., Strohmeier, M., Schäfer, M., Martinovic, I., & Lenders, V. (2022, September). OpenSky Report 2022: Evaluating Aviation Emissions Using Crowdsourced Open Flight Data. Proceedings of the 40th Digital Avionics Systems Conference.
Copy
@inproceedings{sun2022opensky, title = {OpenSky Report 2022: Evaluating Aviation Emissions Using Crowdsourced Open Flight Data}, author = {Sun, Junzi and Basora, Luis and Olive, Xavier and Strohmeier, Martin and Sch{\"a}fer, Matthias and Martinovic, Ivan and Lenders, Vincent}, booktitle = {Proceedings of the 40th Digital Avionics Systems Conference}, year = {2022}, month = sep, link = {https://pure.tudelft.nl/ws/portalfiles/portal/140416750}, tag = {sus} }
Arrival trajectories at five major European airports
Dataset 2022 DOI: 10.4121/20411868.v1
Olive, Xavier ; Basora, Luis ; and Sun, Junzi
4TU.ResearchData
Copy Olive, X., Basora, L., & Sun, J. (2022). Arrival trajectories at five major European airports [Dataset]. 4TU.ResearchData. https://doi.org/10.4121/20411868.v1
Copy
@misc{olive2022arrivaldataset, title = {Arrival trajectories at five major European airports}, author = {Olive, Xavier and Basora, Luis and Sun, Junzi}, publisher = {4TU.ResearchData}, year = {2022}, month = aug, doi = {10.4121/20411868.v1}, link = {https://doi.org/10.4121/20411868.v1}, type = {Dataset}, tag = {sus} }

OpenAP. top: Open Flight Trajectory Optimization for Air Transport and Sustainability Research

Journal 2022 DOI: 10.3390/aerospace9070383

Sun, Junzi
Aerospace

Copy Sun, J. (2022). OpenAP. top: Open Flight Trajectory Optimization for Air Transport and Sustainability Research. Aerospace, 9(7), 383. https://doi.org/10.3390/aerospace9070383

Copy

@article{sun2022top,
  title = {OpenAP. top: Open Flight Trajectory Optimization for Air Transport and Sustainability Research},
  author = {Sun, Junzi},
  journal = {Aerospace},
  volume = {9},
  number = {7},
  pages = {383},
  year = {2022},
  month = jul,
  publisher = {Multidisciplinary Digital Publishing Institute},
  link = {https://doi.org/10.3390/aerospace9070383},
  doi = {10.3390/aerospace9070383},
  tag = {perf, sus}
}

Environmental Impact Optimisation of Flight Plans in a Fixed and Free Route network
Conference 2022
Vergnes, Florent ; Bedouet, Judicaël ; Olive, Xavier ; and Sun, Junzi
In Proceedings of the 10th International Conference for Research in Air Transportation
Copy Vergnes, F., Bedouet, J., Olive, X., & Sun, J. (2022, June). Environmental Impact Optimisation of Flight Plans in a Fixed and Free Route network. Proceedings of the 10th International Conference for Research in Air Transportation.
Copy
@inproceedings{vergnes2022env, title = {Environmental Impact Optimisation of Flight Plans in a Fixed and Free Route network}, author = {Vergnes, Florent and Bedouet, Judicaël and Olive, Xavier and Sun, Junzi}, booktitle = {Proceedings of the 10th International Conference for Research in Air Transportation}, year = {2022}, month = jun, link = {https://research.tudelft.nl/files/126274460/ICRAT2022_paper_22.pdf}, tag = {sus} }
Assessing and Modelling Climate Optimal Flights Using Open Surveillance and Remote Sensing Data
Conference 2022
Roosenbrand, Esther ; Sun, Junzi ; Dedoussi, Irene ; Stam, Daphne ; and Hoekstra, Jacco
In Proceedings of the 10th International Conference for Research in Air Transportation
Copy Roosenbrand, E., Sun, J., Dedoussi, I., Stam, D., & Hoekstra, J. (2022, June). Assessing and Modelling Climate Optimal Flights Using Open Surveillance and Remote Sensing Data. Proceedings of the 10th International Conference for Research in Air Transportation.
Copy
@inproceedings{roosenbrand2022assessing, title = {Assessing and Modelling Climate Optimal Flights Using Open Surveillance and Remote Sensing Data}, author = {Roosenbrand, Esther and Sun, Junzi and Dedoussi, Irene and Stam, Daphne and Hoekstra, Jacco}, booktitle = {Proceedings of the 10th International Conference for Research in Air Transportation}, year = {2022}, month = jun, link = {https://research.tudelft.nl/files/126274533/ICRAT2022_paper_2.pdf}, tag = {sus} }
Data underlying the publication "Global civil aviation emissions estimates for 2017–2020 using ADS-B data"
Dataset 2022 DOI: 10.4121/15015390.v1
Quadros, Flavio Domingos de Azevedo ; Snellen, M. Mirjam ; Sun, Junzi ; and Dedoussi, Irene C
4TU.ResearchData
Copy Quadros, F. D. de A., Snellen, M. M., Sun, J., & Dedoussi, I. C. (2022). Data underlying the publication "Global civil aviation emissions estimates for 2017–2020 using ADS-B data" [Dataset]. 4TU.ResearchData. https://doi.org/10.4121/15015390.v1
Copy
@misc{quadros2022emissionsdataset, title = {Data underlying the publication "Global civil aviation emissions estimates for 2017--2020 using ADS-B data"}, author = {Quadros, Flavio Domingos de Azevedo and Snellen, M. Mirjam and Sun, Junzi and Dedoussi, Irene C}, publisher = {4TU.ResearchData}, year = {2022}, month = may, doi = {10.4121/15015390.v1}, link = {https://doi.org/10.4121/15015390.v1}, type = {Dataset}, tag = {sus} }
Evaluation of Aviation Emissions and Environmental Costs in Europe Using OpenSky and OpenAP
Conference 2021
Sun, Junzi ; and Dedoussi, Irene
In Proceedings of 9th OpenSky Symposium
Copy Sun, J., & Dedoussi, I. (2021, November). Evaluation of Aviation Emissions and Environmental Costs in Europe Using OpenSky and OpenAP. Proceedings of 9th OpenSky Symposium.
Copy
@inproceedings{sun2021euemission, title = {Evaluation of Aviation Emissions and Environmental Costs in Europe Using OpenSky and OpenAP}, author = {Sun, Junzi and Dedoussi, Irene}, booktitle = {Proceedings of 9th OpenSky Symposium}, year = {2021}, month = nov, link = {https://doi.org/10.3390/engproc2021013005}, tag = {sus} }
Fuel Inefficiency Characterisation and Assessment due to Early Execution of Top of Descents
Conference 2021
Dalmau, Ramon ; Sun, Junzi ; and Prats, Xavier
In 14th USA/Europe Air Traffic Management Research and Development Seminar
Copy Dalmau, R., Sun, J., & Prats, X. (2021, September). Fuel Inefficiency Characterisation and Assessment due to Early Execution of Top of Descents. 14th USA/Europe Air Traffic Management Research and Development Seminar.
Copy
@inproceedings{dalmau2021fuel, title = {Fuel Inefficiency Characterisation and Assessment due to Early Execution of Top of Descents}, author = {Dalmau, Ramon and Sun, Junzi and Prats, Xavier}, booktitle = {14th USA/Europe Air Traffic Management Research and Development Seminar}, organization = {FAA/EUROCONTROL}, year = {2021}, month = sep, link = {https://research.tudelft.nl/files/105023510/ATM_Seminar_2021_paper_77.pdf}, tag = {sus} }