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Probabilistic analysis of ambiguities in radar echo direction of arrival from meteors
Umeå University, Faculty of Science and Technology, Department of Physics. Swedish Institute of Space Physics (IRF), Kiruna, Sweden.ORCID iD: 0000-0002-6371-1016
2020 (English)In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 13, no 12, p. 6813-6835Article in journal (Refereed) Published
Abstract [en]

Meteors and hard targets produce coherent radar echoes. If measured with an interferometric radar system, these echoes can be used to determine the position of the target through finding the direction of arrival (DOA) of the incoming echo onto the radar. Depending on the spatial configuration of radar-receiving antennas and their individual gain patterns, there may be an ambiguity problem when determining the DOA of an echo. Radars that are theoretically ambiguity-free are known to still have ambiguities that depend on the total radar signal-to-noise ratio (SNR). In this study, we investigate robust methods which are easy to implement to determine the effect of ambiguities on any hard target DOA determination by interferometric radar systems. We apply these methods specifically to simulate four different radar systems measuring meteor head and trail echoes, using the multiple signal classification (MUSIC) DOA determination algorithm. The four radar systems are the Middle And Upper Atmosphere (MU) radar in Japan, a generic Jones 2.5 lambda specular meteor trail radar configuration, the Middle Atmosphere Alomar Radar System (MAARSY) radar in Norway and the Program of the Antarctic Syowa Mesosphere Stratosphere Troposphere Incoherent Scatter (PANSY) radar in the Antarctic. We also examined a slightly perturbed Jones 2.5 lambda configuration used as a meteor trail echo receiver for the PANSY radar. All the results are derived from simulations, and their purpose is to grant understanding of the behaviour of DOA determination. General results are as follows: there may be a region of SNRs where ambiguities are relevant; Monte Carlo simulation determines this region and if it exists; the MUSIC function peak value is directly correlated with the ambiguous region; a Bayesian method is presented that may be able to analyse echoes from this region; the DOA of echoes with SNRs larger than this region are perfectly determined; the DOA of echoes with SNRs smaller than this region completely fail to be determined; the location of this region is shifted based on the total SNR versus the channel SNR in the direction of the target; and asymmetric subgroups can cause ambiguities, even for ambiguity-free radars. For a DOA located at the zenith, the end of the ambiguous region is located at 17 dB SNR for the MU radar and 3 dB SNR for the PANSY radar. The Jones radars are usually used to measure specular trail echoes far from zenith. The ambiguous region for a DOA at 75.5 degrees elevation and 0 degrees azimuth ends at 12 dB SNR. Using the Bayesian method, it may be possible to analyse echoes down to 4 dB SNR for the Jones configuration when given enough data points from the same target. The PANSY meteor trail echo receiver did not deviate significantly from the generic Jones configuration. The MAARSY radar could not resolve arbitrary DOAs su degrees ciently well enough to determine a stable region. However, if the DOA search is restricted to 70 degrees elevation or above by assumption, stable DOA determination occurs above 15 dB SNR.

Place, publisher, year, edition, pages
Nicolaus Copernicus University Press, 2020. Vol. 13, no 12, p. 6813-6835
National Category
Signal Processing Subatomic Physics
Identifiers
URN: urn:nbn:se:umu:diva-178313DOI: 10.5194/amt-13-6813-2020ISI: 000600076600002Scopus ID: 2-s2.0-85097912453OAI: oai:DiVA.org:umu-178313DiVA, id: diva2:1515829
Available from: 2021-01-11 Created: 2021-01-11 Last updated: 2023-03-23Bibliographically 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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