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Penttilä, A., Muinonen, K., Granvik, M., Gray, Z., Bagnulo, S., Kolokolova, L. & Moreno, F. (2024). Modeling Linear Polarization of the Didymos–Dimorphos System before and after the DART Impact. The Planetary Science Journal, 5(1), Article ID 27.
Open this publication in new window or tab >>Modeling Linear Polarization of the Didymos–Dimorphos System before and after the DART Impact
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2024 (English)In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 5, no 1, article id 27Article in journal (Refereed) Published
Abstract [en]

We analyze the polarization observations of the Didymos–Dimorphos system before and after the impact by the NASA Double Asteroid Redirection Test spacecraft on Dimorphos. We fit empirical polarization phase curve models and statistically confirm the discovery by Gray et al. about the degree of linear polarization of the system decreasing on the impact and remaining altered for at least 30 days post-impact. With numerical simulations of particles in the geometric optics domain, we estimate the dominant size of the particles either in the regolith of Didymos and Dimorphos or in the impact-driven ejecta cloud to be several hundred micrometers. The observed change between the pre-impact and post-impact systems indicates either a decrease in average particle size of some tens of micrometers or a decreased level of space weathering.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2024
National Category
Meteorology and Atmospheric Sciences
Research subject
Onboard Space Systems
Identifiers
urn:nbn:se:ltu:diva-104170 (URN)10.3847/psj/ad1757 (DOI)
Funder
Academy of Finland, 1345115
Note

Validerad;2024;Nivå 1;2024-02-05 (hanlid);

Funder: NASA DART PSP (80NSSC21K1131);

Full text license: CC BY

Available from: 2024-02-05 Created: 2024-02-05 Last updated: 2024-02-05Bibliographically approved
Nesvorný, D., Vokrouhlický, D., Shelly, F., Deienno, R., Bottke, W. F., Christensen, E., . . . Granvik, M. (2024). NEOMOD 2: An updated model of Near-Earth Objects from a decade of Catalina Sky Survey observations. Icarus, 411, Article ID 115922.
Open this publication in new window or tab >>NEOMOD 2: An updated model of Near-Earth Objects from a decade of Catalina Sky Survey observations
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2024 (English)In: Icarus, ISSN 0019-1035, E-ISSN 1090-2643, Vol. 411, article id 115922Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Academic Press Inc., 2024
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Onboard Space Systems
Identifiers
urn:nbn:se:ltu:diva-103516 (URN)10.1016/j.icarus.2023.115922 (DOI)2-s2.0-85180423182 (Scopus ID)
Note

Funder: NASA (21-11058S); Array (21-11058S)

Available from: 2024-01-08 Created: 2024-01-08 Last updated: 2024-01-08
Gray, Z., Bagnulo, S., Granvik, M., Cellino, A., Jones, G. H., Kolokolova, L., . . . Snodgrass, C. (2024). Polarimetry of Didymos–Dimorphos: Unexpected Long-term Effects of the DART Impact. The Planetary Science Journal, 5(1), Article ID 18.
Open this publication in new window or tab >>Polarimetry of Didymos–Dimorphos: Unexpected Long-term Effects of the DART Impact
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2024 (English)In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 5, no 1, article id 18Article in journal (Refereed) Published
Abstract [en]

We have monitored the Didymos–Dimorphos binary system in imaging polarimetric mode before and after the impact from the Double Asteroid Redirection Test mission. A previous spectropolarimetric study showed that the impact caused a dramatic drop in polarization. Our longer-term monitoring shows that the polarization of the post-impact system remains lower than the pre-impact system even months after the impact, suggesting that some fresh ejecta material remains in the system at the time of our observations, either in orbit or settled on the surface. The slope of the post-impact polarimetric curve is shallower than that of the pre-impact system, implying an increase in albedo of the system. This suggests that the ejected material is composed of smaller and possibly brighter particles than those present on the pre-impact surface of the asteroid. Our polarimetric maps show that the dust cloud ejected immediately after the impact polarizes light in a spatially uniform manner (and at a lower level than pre-impact). Later maps exhibit a gradient in polarization between the photocentre (which probes the asteroid surface) and the surrounding cloud and tail. The polarization occasionally shows some small-scale variations, the source of which is not yet clear. The polarimetric phase curve of Didymos–Dimorphos resembles that of the S-type asteroid class.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2024
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Onboard Space Systems
Identifiers
urn:nbn:se:ltu:diva-103980 (URN)10.3847/psj/ad0f18 (DOI)
Note

Validerad;2024;Nivå 1;2024-01-29 (hanlid);

Funder: STFC (ST/W001004/1); Academy of Finland (Research Council of Finland) (345115, 336546);  NASA DART PS Program (80NSSC21K1131); (PID2021-123370OB-100/AEI/10.13039/501100011033/FEDER),

Full text license: CC BY

Available from: 2024-01-29 Created: 2024-01-29 Last updated: 2024-01-29Bibliographically approved
Lagain, A., Devillepoix, H. A. .., Vernazza, P., Robertson, D., Granvik, M., Pokorny, P., . . . Benedix, G. K. (2024). Recalibration of the lunar chronology due to spatial cratering-rate variability. Icarus, 411, Article ID 115956.
Open this publication in new window or tab >>Recalibration of the lunar chronology due to spatial cratering-rate variability
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2024 (English)In: Icarus, ISSN 0019-1035, E-ISSN 1090-2643, Vol. 411, article id 115956Article in journal (Refereed) Published
Abstract [en]

Cratering chronologies are used to derive the history of planetary bodies and assume an isotropic flux of impactors over the entire surface of the Moon. The impactor population is largely dominated by near-Earth-objects (NEOs) since ∼3.5 billion years ago. However, lunar impact probabilities from the currently known NEO population show an excess of impacts close to the poles compared to the equator as well as a latitudinal dependency of the approach angle of impactors. This is accompanied by a variation of the impact flux and speed with the distance from the apex due to the synchronicity of the lunar orbit around the Earth. Here, we compute the spatial dependency of the cratering rate produced by such variabilities and recalibrate the lunar chronology. We show that it allows to reconcile the crater density measured at mid-latitudes around the Chang'e-5 landing site with the age of the samples collected by this mission. Our updated chronology leads to differences in model ages of up to 30% compared to other chronology systems. The modeled cratering rate variability is then compared with the distribution of lunar craters younger than ∼1 Ma, 1 Ga and 4 Ga. The general trend of the cratering distribution is consistent with the one obtained from dynamical models of NEOs, thus potentially reflecting a nonuniform distribution of orbital parameters of ancient impactor populations, beyond 3.5 Ga ago, i.e., planetary leftovers and cometary bodies. If the nonuniformity of the cratering rate could be tested elsewhere in the Solar System, the recalibrated lunar chronology, corrected from spatial variations of the impact flux and approach conditions of impactors, could be extrapolated on other terrestrial bodies such as Mercury and Mars, at least over the last 3.5 billion years. The modeled cratering rate presented here has strong implications for interpreting results of the Artemis program, aiming to explore the South Pole of our satellite, in particular when it will come to link the radiometric age of the samples collected in this region and the crater density of the sampled units.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Moon, Impact craters, Impact flux, Chang'e 5, Chronology
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Onboard Space Systems
Identifiers
urn:nbn:se:ltu:diva-103776 (URN)10.1016/j.icarus.2024.115956 (DOI)
Funder
Australian Research Council, DP210100336
Note

Validerad;2024;Nivå 2;2024-01-17 (signyg);

Funder: Curtin University; the Western Australian Government; the Australian Government; the Pawsey Supercomputing Centre ADACS (Astronomy Data and Compute Services); Initiative d'Excellence d'Aix-Marseille Université (A*MIDEX AMX-21-RID-O47); NASA  (grant nos. 80NSSC21K0153, 80NSSC19M0217, 80GSFC21M000, 80NSSC19M0089); CSIRO;

Full text license: CC BY-NC-ND

Available from: 2024-01-17 Created: 2024-01-17 Last updated: 2024-01-17Bibliographically approved
Jones, G. H., Snodgrass, C., Tubiana, C., Küppers, M., Kawakita, H., Lara, L. M., . . . Ji, H. (2024). The Comet Interceptor Mission. Space Science Reviews, 220(1), Article ID 9.
Open this publication in new window or tab >>The Comet Interceptor Mission
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2024 (English)In: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 220, no 1, article id 9Article in journal (Refereed) Published
Abstract [en]

Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum Δ V capability of 600 ms − 1 . Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule.

Place, publisher, year, edition, pages
Springer Nature, 2024
Keywords
Comets, Spacecraft, Instruments – spaceborne and space research
National Category
Astronomy, Astrophysics and Cosmology Fusion, Plasma and Space Physics Aerospace Engineering
Research subject
Onboard Space Systems
Identifiers
urn:nbn:se:ltu:diva-104187 (URN)10.1007/s11214-023-01035-0 (DOI)38282745 (PubMedID)2-s2.0-85183417097 (Scopus ID)
Note

For funding information, see: https://link.springer.com/article/10.1007/s11214-023-01035-0;

Full text license: CC BY 4.0;

Available from: 2024-02-06 Created: 2024-02-06 Last updated: 2024-02-06
Granvik, M. & Walsh, K. J. (2024). Tidal Disruption of Near-Earth Asteroids during Close Encounters with Terrestrial Planets. Astrophysical Journal Letters, 960(2), Article ID L9.
Open this publication in new window or tab >>Tidal Disruption of Near-Earth Asteroids during Close Encounters with Terrestrial Planets
2024 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 960, no 2, article id L9Article in journal (Refereed) Published
Abstract [en]

Numerical modeling has long suggested that gravitationally bound (or so-called rubble-pile) near-Earth asteroids (NEAs) can be destroyed by tidal forces during close and slow encounters with terrestrial planets. However, tidal disruptions of NEAs have never been directly observed nor have they been directly attributed to any families of NEAs. Here we show population-level evidence for the tidal disruption of NEAs during close encounters with Earth and Venus. Debiased model distributions of NEA orbits and absolute magnitudes based on observations by the Catalina Sky Survey during 2005–2012 underpredict the number of NEAs with perihelion distances coinciding with the semimajor axes of Venus and Earth. A detailed analysis of the orbital distributions of the excess NEAs shows that their characteristics agree with the prediction for tidal disruptions, and they cannot be explained by observational selection effects or orbital dynamics. Accounting for tidal disruptions in evolutionary models of the NEA population partly bridges the gap between the predicted rate of impacts by asteroids with diameters of tens of meters and observed statistics of fireballs in the same size range.

Place, publisher, year, edition, pages
American Astronomical Society, 2024
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Onboard Space Systems
Identifiers
urn:nbn:se:ltu:diva-103520 (URN)10.3847/2041-8213/ad151b (DOI)
Funder
Swedish Research Council, 2022-04615
Note

Validerad;2024;Nivå 2;2024-01-17 (signyg)

Funding: NASA Solar System Exploration Research Virtual Institute node Project ESPRESSO (grant nos. 80ARC0M0008); National Science Foundation (grant nos. 2108440);

Full text license: CC BY: 4.0

Available from: 2024-01-09 Created: 2024-01-09 Last updated: 2024-01-17Bibliographically approved
Farnocchia, D., Seligman, D. Z., Granvik, M., Hainaut, O., Meech, K. J., Micheli, M., . . . Wainscoat, R. J. (2023). (523599) 2003 RM: The Asteroid that Wanted to be a Comet. The Planetary Science Journal, 4(2), Article ID 29.
Open this publication in new window or tab >>(523599) 2003 RM: The Asteroid that Wanted to be a Comet
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2023 (English)In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 4, no 2, article id 29Article in journal (Refereed) Published
Abstract [en]

We report a statistically significant detection of nongravitational acceleration on the subkilometer near-Earth asteroid (523599) 2003 RM. Due to its orbit, 2003 RM experiences favorable observing apparitions every 5 yr. Thus, since its discovery, 2003 RM has been extensively tracked with ground-based optical facilities in 2003, 2008, 2013, and 2018. We find that the observed plane-of-sky positions cannot be explained with a purely gravity-driven trajectory. Including a transverse nongravitational acceleration allows us to match all observational data, but its magnitude is inconsistent with perturbations typical of asteroids such as the Yarkovsky effect or solar radiation pressure. After ruling out that the orbital deviations are due to a close approach or collision with another asteroid, we hypothesize that this anomalous acceleration is caused by unseen cometary outgassing. A detailed search for evidence of cometary activity with archival and deep observations from the Panoramic Survey Telescope and Rapid Response System and the Very Large Telescope does not reveal any detectable dust production. However, the best-fitting H2O sublimation model allows for brightening due to activity consistent with the scatter of the data. We estimate the production rate required for H2O outgassing to power the acceleration and find that, assuming a diameter of 300 m, 2003 RM would require Q(H2O) similar to 10(23) molec s(-1) at perihelion. We investigate the recent dynamical history of 2003 RM and find that the object most likely originated in the mid-to-outer main belt (similar to 86% probability) as opposed to from the Jupiter-family comet region (similar to 11% probability). Further observations, especially in the infrared, could shed light on the nature of this anomalous acceleration.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2023
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Onboard Space Systems
Identifiers
urn:nbn:se:ltu:diva-95863 (URN)10.3847/PSJ/acb25b (DOI)000930641700001 ()
Note

Validerad;2023;Nivå 2;2023-03-15 (hanlid);

Funder: National Aeronautics and Space Administration (80NM0018D0004 and NASA-80NSSC18K0853); National Science Foundation (AST-17152); NASA (80NSSC19K0444); NASA Goddard Space Flight Center (NNX17AL71A)

Available from: 2023-03-13 Created: 2023-03-13 Last updated: 2023-05-05Bibliographically approved
Deshapriya, J. D., Perna, D., Bott, N., Hasselmann, P. H., Granvik, M., Dotto, E., . . . Epifani, E. M. (2023). Clustering the properties of near-Earth objects: physico-dynamical links among NEOs. Astronomy and Astrophysics, 674, Article ID A50.
Open this publication in new window or tab >>Clustering the properties of near-Earth objects: physico-dynamical links among NEOs
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2023 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 674, article id A50Article in journal (Refereed) Published
Abstract [en]

Context. At present, near-Earth objects (NEOs) are being discovered at an ever-increasing rate. However, their physical characterisation is still significantly lagging behind. In particular, the taxonomic classification of newly discovered NEOs is of great importance with regard to improving our understanding of the population of NEOs.

Aims. In this context, our goal is to probe potential links between orbital properties of NEOs and their composition. We investigate whether we can make a reasonable guess about the taxonomic class of an NEO upon its discovery with a decent orbital accuracy.

Methods. We used a G-mode multivariate statistical clustering method to find homogeneous clusters in a dataset composed of orbital elements of NEOs. We adopted two approaches, using two sets of variables as inputs to the G-mode method. In each approach, we analysed the available taxonomic distribution of resulting clusters to find potential correlations with several unique parameters that distinctively characterise NEOs. We then applied a dynamical model on the same clusters to trace their escape regions.

Results. Approach 1 (A1) led us to obtain NEO clusters that can be linked to a primitive composition. This result was further strengthened by the dynamical model, which mapped outer-belt sources as escape regions for these clusters. We remark on the finding of a cluster akin to S-type NEOs in highly eccentric orbits during the same approach (A1). Two clusters, one with small NEOs in terrestriallike orbits and one with relatively high inclinations, were found to be common to both approaches. Approach 2 (A2) revealed three clusters that are only separable by their arguments of perihelion. Taken altogether, they make up the majority of known Atira asteroids.

Conclusions. For an NEO whose orbit is relatively well determined, we propose a model to determine whether the taxonomy of an NEO is siliceous or primitive if the orbital elements of the NEO fall within the presented combinations of inclination, eccentricity, and semi-major axis ranges.

Place, publisher, year, edition, pages
EDP Sciences, 2023
Keywords
minor planets, asteroids: general, techniques: spectroscopic, methods: statistical
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Onboard Space Systems
Identifiers
urn:nbn:se:ltu:diva-99347 (URN)10.1051/0004-6361/202245316 (DOI)001000113500007 ()2-s2.0-85162083024 (Scopus ID)
Funder
EU, Horizon 2020, 870403
Note

Validerad;2023;Nivå 2;2023-08-09 (joosat);

Funder: Agenzia Spaziale Italiana (ASI, contract no. 2017-37-H.0 CUP F82F17000630005)

Licens fulltext: CC BY License

Available from: 2023-08-09 Created: 2023-08-09 Last updated: 2023-08-09Bibliographically approved
Li, J.-Y., Hirabayashi, M., Farnham, T. L., Sunshine, J. M., Knight, M. M., Tancredi, G., . . . Trigo-Rodríguez, J. M. (2023). Ejecta from the DART-produced active asteroid Dimorphos. Nature, 616, 452-456
Open this publication in new window or tab >>Ejecta from the DART-produced active asteroid Dimorphos
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2023 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 616, p. 452-456Article in journal (Refereed) Published
Abstract [en]

Some active asteroids have been proposed to be formed as a result of impact events1. Because active asteroids are generally discovered by chance only after their tails have fully formed, the process of how impact ejecta evolve into a tail has, to our knowledge, not been directly observed. The Double Asteroid Redirection Test (DART) mission of NASA2, in addition to having successfully changed the orbital period of Dimorphos3, demonstrated the activation process of an asteroid resulting from an impact under precisely known conditions. Here we report the observations of the DART impact ejecta with the Hubble Space Telescope from impact time T + 15 min to T + 18.5 days at spatial resolutions of around 2.1 km per pixel. Our observations reveal the complex evolution of the ejecta, which are first dominated by the gravitational interaction between the Didymos binary system and the ejected dust and subsequently by solar radiation pressure. The lowest-speed ejecta dispersed through a sustained tail that had a consistent morphology with previously observed asteroid tails thought to be produced by an impact4,5. The evolution of the ejecta after the controlled impact experiment of DART thus provides a framework for understanding the fundamental mechanisms that act on asteroids disrupted by a natural impact1,6.

Place, publisher, year, edition, pages
Springer Nature, 2023
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Onboard Space Systems
Identifiers
urn:nbn:se:ltu:diva-97032 (URN)10.1038/s41586-023-05811-4 (DOI)36858074 (PubMedID)2-s2.0-85150810493 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-12-12 (hanlid);

For funding information see: https://doi.org/10.1038/s41586-023-05811-4;

Full text license: CC BY

Available from: 2023-05-08 Created: 2023-05-08 Last updated: 2023-12-12Bibliographically approved
Pöntinen, M., Granvik, M., Nucita, A. A., Conversi, L., Altieri, B., Carry, B., . . . Scottez, V. (2023). Euclid: Identification of asteroid streaks in simulated images using deep learning. Astronomy and Astrophysics, 679, Article ID A135.
Open this publication in new window or tab >>Euclid: Identification of asteroid streaks in simulated images using deep learning
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2023 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 679, article id A135Article in journal (Refereed) Published
Abstract [en]

The material composition of asteroids is an essential piece of knowledge in the quest to understand the formation and evolution of the Solar System. Visual to near-infrared spectra or multiband photometry is required to constrain the material composition of asteroids, but we currently have such data, especially in the near-infrared wavelengths, for only a limited number of asteroids. This is a significant limitation considering the complex orbital structures of the asteroid populations. Up to 150 000 asteroids will be visible in the images of the upcoming ESA Euclid space telescope, and the instruments of Euclid will offer multiband visual to near-infrared photometry and slitless near-infrared spectra of these objects. Most of the asteroids will appear as streaks in the images. Due to the large number of images and asteroids, automated detection methods are needed. A non-machine-learning approach based on the Streak Det software was previously tested, but the results were not optimal for short and/or faint streaks. We set out to improve the capability to detect asteroid streaks in Euclid images by using deep learning. We built, trained, and tested a three-step machine-learning pipeline with simulated Euclid images. First, a convolutional neural network (CNN) detected streaks and their coordinates in full images, aiming to maximize the completeness (recall) of detections. Then, a recurrent neural network (RNN) merged snippets of long streaks detected in several parts by the CNN. Lastly, gradient-boosted trees (XGBoost) linked detected streaks between different Euclid exposures to reduce the number of false positives and improve the purity (precision) of the sample. The deep-learning pipeline surpasses the completeness and reaches a similar level of purity of a non-machine-learning pipeline based on the StreakDet software. Additionally, the deep-learning pipeline can detect asteroids 0.25–0.5 magnitudes fainter than StreakDet. The deep-learning pipeline could result in a 50% increase in the number of detected asteroids compared to the StreakDet software. There is still scope for further refinement, particularly in improving the accuracy of streak coordinates and enhancing the completeness of the final stage of the pipeline, which involves linking detections across multiple exposures.

Place, publisher, year, edition, pages
EDP Sciences, 2023
Keywords
methods: data analysis, techniques: image processing, minor planets, asteroids: general, space vehicles, surveys, methods: numerical
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Onboard Space Systems
Identifiers
urn:nbn:se:ltu:diva-103202 (URN)10.1051/0004-6361/202347551 (DOI)
Funder
Academy of Finland, 316292, 299543
Note

Validerad;2023;Nivå 2;2023-12-12 (marisr);

Funder: Vilho, Yrjö, and Kalle Väisälä Foundation;

Full text license: CC BY

Available from: 2023-12-05 Created: 2023-12-05 Last updated: 2023-12-12Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5624-1888

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