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Resolving the ambiguous direction of arrival of weak meteor radar trail echoes
Umeå University, Faculty of Science and Technology, Department of Physics. Swedish Institute of Space Physics (IRF), Kiruna, Sweden.ORCID iD: 0000-0002-6371-1016
Swedish Institute of Space Physics (IRF), Kiruna, Sweden.
Sodankylä Geophysical Observatory, Sodankylä, Finland.
Department of Physics and Astronomy, University of Leicester, Leicester, United Kingdom.
2021 (English)In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 14, no 5, p. 3583-3596Article in journal (Refereed) Published
Abstract [en]

Meteor phenomena cause ionized plasmas that can be roughly divided into two distinctly different regimes: a dense and transient plasma region co-moving with the ablating meteoroid and a trail of diffusing plasma left in the atmosphere and moving with the neutral wind. Interferometric radar systems are used to observe the meteor trails and determine their positions and drift velocities. Depending on the spatial configuration of the receiving antennas and their individual gain patterns, the voltage response can be the same for several different plane wave directions of arrival (DOAs), thereby making it impossible to determine the correct direction. A low signal-to-noise ratio (SNR) can create the same effect probabilistically even if the system contains no theoretical ambiguities. Such is the case for the standard meteor trail echo data products of the Sodankyl Geophysical Observatory SKiYMET all-sky interferometric meteor radar. Meteor trails drift slowly enough in the atmosphere and allow for temporal integration, while meteor head echo targets move too fast. Temporal integration is a common method to increase the SNR of radar signals. For meteor head echoes, we instead propose to use direct Monte Carlo (DMC) simulations to validate DOA measurements. We have implemented two separate temporal integration methods and applied them to 2222 events measured by the Sodankyl meteor radar to simultaneously test the usefulness of such DMC simulations on cases where temporal integration is possible, validate the temporal integration methods, and resolve the ambiguous SKiYMET data products. The two methods are the temporal integration of the signal spatial correlations and matchedfilter integration of the individual radar channel signals. The results are compared to Bayesian inference using the DMC simulations and the standard SkiYMET data products. In the examined data set, 13% of the events were indicated as ambiguous. Out of these, 13% contained anomalous signals. In 95% of all ambiguous cases with a nominal signal, the three methods found one and the same output DOA, which was also listed as one of the ambiguous possibilities in the SkiYMET analysis. In all unambiguous cases, the results from all methods concurred.

Place, publisher, year, edition, pages
Copernicus GmbH , 2021. Vol. 14, no 5, p. 3583-3596
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:umu:diva-183723DOI: 10.5194/amt-14-3583-2021ISI: 000654333000002Scopus ID: 2-s2.0-85106154126OAI: oai:DiVA.org:umu-183723DiVA, id: diva2:1558553
Available from: 2021-05-31 Created: 2021-05-31 Last updated: 2023-09-05Bibliographically approved
In thesis
1. From meteors to space safety: dynamical models and radar measurements of space objects
Open this publication in new window or tab >>From meteors to space safety: dynamical models and radar measurements of space objects
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Från meteorer till rymdlägesbild : dynamiska modeller och radarmätningar av rymdobjekt
Abstract [en]

Every day the Earth's atmosphere is bombarded by 10-200 metric tons of dust-sized particles and larger pieces of material from space called meteoroids. Dust and meteoroids come from parent bodies such as comets and asteroids, which are remnants from the formation of the solar system. In addition to natural objects, geospace contains artificial satellites and space debris that needs to be monitored to reduce the risk of collisions. Studies of all these kinds of space objects form a cross-disciplinary research field that stretches from meteors to space safety

The primary goal of this thesis has been to rigorously connect measurements and their uncertainties with high-level analysis and dynamical simulations of distributions.

An automated radar data analysis algorithm was developed for meteor head echo measurements. The analysis algorithm is able to produce realistic uncertainties for each individual meteor event, including the meteoroid orbit. Many of the resulting probability distributions are non-Gaussian, which needs to be accounted for. The analysis algorithm was applied to interferometric high-power large-aperture MU radar data in a case study on high altitude meteors. The study found that 74 out of 106,000 meteors appeared higher than 130 km and a few confirmed detections reached up to 150 km altitude.

Comet 21P/Giacobini–Zinner is the parent body of the meteoroid stream giving rise to the October Draconid meteor shower. The meteoroid stream was simulated accounting for parent body orbital uncertainties to estimate meteor shower parameters. The simulation was able to model the unexpected mass distribution observed in the 2011 and 2012 October Draconids. It also successfully predicted a meteor outburst in 2018. Further, methods to reduce the computation time of meteoroid stream simulations using importance sampling were derived and implemented on a test model.

EISCAT radar measurements were performed to study space debris from the Kosmos-1408 satellite, which had been destroyed and fragmented in orbit on 15 November, 2021. A novel method to estimate the size distribution of debris objects was developed. Data from two EISCAT radars were used to demonstrate a new initial orbit determination technique, yielding good agreement with known catalogue orbits. Finally, the detectability of near-Earth objects (NEOs) with the EISCAT~3D radar currently under construction was simulated. It was predicted that as many as seven temporarily captured NEOs, i.e. minimoons, could be discovered per year depending on the amount of allocated observation time. The predictions also show that hundreds of NEOs could be tracked yearly to improve their orbits.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2022. p. 79
Series
IRF Scientific Report, ISSN 0284-1703 ; 315
Keywords
Meteors, meteor shower, atmosphere, meteoroids, meteoroid stream, small-body dynamics, solar system, comets, asteroids, near-Earth objects, space safety, space debris, radar, MU, EISCAT
National Category
Astronomy, Astrophysics and Cosmology Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-200702 (URN)978-91-7855-902-2 (ISBN)978-91-7855-903-9 (ISBN)
Public defence
2022-11-25, Ljusårssalen, Institutet för rymdfysik, Bengt Hultqvists väg 1, Kiruna, 09:00 (English)
Opponent
Supervisors
Available from: 2022-11-04 Created: 2022-10-31 Last updated: 2022-11-01Bibliographically approved

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Kastinen, Daniel

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