scholarly journals Determination of meteor-head echo trajectories using the interferometric capabilities of MAARSY

2013 ◽  
Vol 31 (10) ◽  
pp. 1843-1851 ◽  
Author(s):  
C. Schult ◽  
G. Stober ◽  
J. L. Chau ◽  
R. Latteck
Keyword(s):  
Middle Atmosphere ◽  
Radar System ◽  
Neutral Atmosphere ◽  
Plasma Irregularities ◽  
Radar Systems ◽  
Radar Echoes ◽  
High Kinetic Energy ◽  
Head Echo ◽  
Sporadic Meteors

Abstract. During the flight of a meteoroid through the neutral atmosphere, the high kinetic energy is sufficient to ionize the meteoric constituents. Radar echoes coming from plasma irregularities surrounding the meteoroids are called meteor-head echoes, and can be detected by HPLA radar systems. Measurements of these echoes were conducted with MAARSY (Middle Atmosphere Alomar Radar System) in December 2010. The interferometric capabilities of the radar system permit the determination of the meteor trajectories within the radar beam with high accuracy. The received data are used to gain information about entry velocities, source radiants, observation heights and other meteoroid parameters. Our preliminary results indicate that the majority of meteors have masses between 10−10 and 10−3 kg and the mean masses of the sporadic meteors and Gemenids meteors are ∼10−8 kg.

scholarly journals Determination of meteoroid physical properties from tristatic radar observations

2008 ◽  
Vol 26 (8) ◽  
pp. 2217-2228 ◽  
Author(s):  
J. Kero ◽  
C. Szasz ◽  
A. Pellinen-Wannberg ◽  
G. Wannberg ◽  
A. Westman ◽  
...  
Keyword(s):  
Cross Sections ◽  
Equation Of Motion ◽  
Momentum Equation ◽  
Radar System ◽  
Radar Target ◽  
Radar Cross Sections ◽  
The Common ◽  
Head Echo ◽  
Uhf Radar

Abstract. In this work we give a review of the meteor head echo observations carried out with the tristatic 930 MHz EISCAT UHF radar system during four 24 h runs between 2002 and 2005 and compare these with earlier observations. A total number of 410 tristatic meteors were observed. We describe a method to determine the position of a compact radar target in the common volume monitored by the three receivers and demonstrate its applicability for meteor studies. The inferred positions of the meteor targets have been utilized to estimate their velocities, decelerations and directions of arrival as well as their radar cross sections with unprecedented accuracy. The velocity distribution of the meteoroids is bimodal with peaks at 35–40 km/s and 55–60 km/s, and ranges from 19–70 km/s. The estimated masses are between 10−9–10−5.5 kg. There are very few detections below 30 km/s. The observations are clearly biased to high-velocity meteoroids, but not so biased against slow meteoroids as has been presumed from previous tristatic measurements. Finally, we discuss how the radial deceleration observed with a monostatic radar depends on the meteoroid velocity and the angle between the trajectory and the beam. The finite beamwidth leads to underestimated meteoroid masses if radial velocity and deceleration of meteoroids approaching the radar are used as estimates of the true quantities in a momentum equation of motion.

A meteoroid stream survey using meteor head echo observations from the Middle Atmosphere ALOMAR Radar System (MAARSY)

Icarus ◽  
2018 ◽  
Vol 309 ◽  
pp. 177-186 ◽  
Author(s):  
Carsten Schult ◽  
Peter Brown ◽  
Petr Pokorný ◽  
Gunter Stober ◽  
Jorge L. Chau
Keyword(s):  
Middle Atmosphere ◽  
Radar System ◽  
Meteoroid Stream ◽  
Head Echo

scholarly journals Probabilistic analysis of ambiguities in radar echo direction of arrival from meteors

2020 ◽  
Vol 13 (12) ◽  
pp. 6813-6835
Author(s):  
Daniel Kastinen ◽  
Johan Kero
Keyword(s):  
Bayesian Method ◽  
Middle Atmosphere ◽  
Direction Of Arrival ◽  
Radar System ◽  
Stable Region ◽  
Radar Signal ◽  
Radar Systems ◽  
Mu Radar ◽  
Meteor Trail ◽  
The Antarctic

Abstract. 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 2.5λ 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 2.5λ 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∘ elevation and 0∘ 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 sufficiently well enough to determine a stable region. However, if the DOA search is restricted to 70∘ elevation or above by assumption, stable DOA determination occurs above 15 dB SNR.

scholarly journals Middle atmospheric changes caused by the January and March 2012 solar proton events

2013 ◽  
Vol 13 (9) ◽  
pp. 23251-23293 ◽  
Author(s):  
C. H. Jackman ◽  
C. E. Randall ◽  
V. L. Harvey ◽  
S. Wang ◽  
E. L. Fleming ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Middle Atmosphere ◽  
Michelson Interferometer ◽  
Peroxy Radical ◽  
Solar Proton ◽  
Proton Event ◽  
Neutral Atmosphere ◽  
Cycle 24 ◽  
Atmospheric Changes ◽  
D Model

Abstract. The recent 23–30 January and 7–11 March 2012 solar proton event (SPE) periods were substantial and caused significant impacts on the middle atmosphere. These were the two largest SPE periods of solar cycle 24 so far. The highly energetic solar protons produced considerable ionization of the neutral atmosphere as well as HOx (H, OH, HO2) and NOx (N, NO, NO2). We compute a NOx production of 1.9 and 2.1 Gigamoles due to these SPE periods in January and March 2012, respectively, which places these SPE periods among the 12 largest in the past 50 yr. Aura Microwave Limb Sounder (MLS) observations of the peroxy radical, HO2, show significant enhancements of > 0.9 ppbv in the northern polar mesosphere as a result of these SPE periods. Both MLS measurements and Goddard Space Flight Center (GSFC) two-dimensional (2-D) model predictions indicated middle mesospheric ozone decreases of > 20% for several days in the northern polar region with maximum depletions > 60% over 1–2 days as a result of the HOx produced in both the January and March 2012 SPE periods. The SCISAT-1 Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE) and the Envisat Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instruments measured NO and NO2 (~ NOx), which indicated enhancements of over 20 ppbv in most of the northern polar mesosphere for several days as a result of these SPE periods. The GSFC 2-D model was used to predict the medium-term (~ months) influence and showed that the polar middle atmosphere ozone was most affected by these solar events in the Southern Hemisphere due to the increased downward motion in the fall and early winter. The downward transport moved the SPE-produced NOy to lower altitudes and led to predicted modest destruction of ozone (5–9%) in the upper stratosphere days to weeks after the March 2012 event. Total ozone reductions were predicted to be a maximum of 1% in 2012 due to these SPEs.

scholarly journals Radar system with dedicated planar traveling wave antennas for elderly people monitoring

2020 ◽  
Vol 18 ◽  
pp. 97-110
Author(s):  
Sassan Schäfer ◽  
Simon Müller ◽  
Daniel Schmiech ◽  
Andreas R. Diewald
Keyword(s):  
Elderly People ◽  
Antenna Arrays ◽  
Traveling Wave ◽  
Radar System ◽  
Propagation Path ◽  
Design Parameters ◽  
Microstrip Technology ◽  
Actual Object ◽  
Radar Systems ◽  
24 Ghz

Abstract. Radar systems for contactless vital sign monitoring are well known and an actual object of research. These radar-based sensors could be used for monitoring of elderly people in their homes but also for detecting the activity of prisoners and to control electrical devices (light, audio, etc.) in smart living environments. Mostly these sensors are foreseen to be mounted on the ceiling in the middle of a room. In retirement homes the rooms are mostly rectangular and of standardized size. Furniture like beds and seating are found at the borders or the corners of the room. As the propagation path from the center of the room ceiling to the borders and corners of a room is 1.4 and 1.7 time longer the power reflected by people located there is 6 or even 10 dB lower than if located in the center of the room. Furthermore classical antennas in microstrip technology are strengthening radiation in broadside direction. Radar systems with only one single planar antenna must be mounted horizontally aligned when measuring in all directions. Thus an antenna pattern which is increasing radiation in the room corners and borders for compensation of free space loss is needed. In this contribution a specification of classical room sizes in retirement homes are given. A method for shaping the antenna gain in the E-plane by an one-dimensional series-fed traveling wave patch array and in the H-plane by an antenna feeding network for improvement of people detection in the room borders and corners is presented for a 24 GHz digital beamforming (DBF) radar system. The feeding network is a parallel-fed power divider for microstrip patch antennas at 24 GHz. Both approaches are explained in theory. The design parameters and the layout of the antennas are given. The simulation of the antenna arrays are executed with CST MWS. Simulations and measurements of the proposed antennas are compared to each other. Both antennas are used for the transmit and the receive channel either. The sensor topology of the radar system is explained. Furthermore the measurement results of the protoype are presented and discussed.

scholarly journals Probabilistic analysis of ambiguities in radar echo direction of arrival from meteors

2020 ◽  
Author(s):  
Daniel Kastinen ◽  
Johan Kero
Keyword(s):  
Bayesian Method ◽  
Direction Of Arrival ◽  
Radar System ◽  
Stable Region ◽  
Radar Signal ◽  
Ambient Atmosphere ◽  
Radar Systems ◽  
Mu Radar ◽  
Meteor Trail ◽  
The Antarctic

Abstract. 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. If the DOA of meteor trail plasma drifting with the ambient atmosphere is determined, the neutral wind at the observation altitude can be calculated. Specular meteor trail radars have become widespread scientific instruments to study atmospheric dynamics. Meteor head echo measurements also contribute to studies of the atmosphere as the meteoroid input of extraterrestrial material is relevant for a plethora of atmospheric phenomena. 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 2.5λ specular meteor trail radar configuration, the Middle Atmosphere Alomar Radar System (MAARSY) radar in Norway and the The Program of the Antarctic Syowa Mesosphere Stratosphere Troposphere Incoherent Scatter (PANSY) radar in the Antarctic. We also examined a slightly perturbed Jones 2.5λ 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: 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 then this region are perfectly determined; the DOA of echoes with SNRs smaller then 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; 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° elevation and 0° 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, 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 sufficiently well to determine a stable region. However, if the DOA search is restricted to 70° elevation or above by assumption, stable DOA determination occurs above 15 dB SNR.

High spatiotemporal radar observation of the polar summer mesosphere using MAARSY in a MIMO configuration

2021 ◽  
Author(s):  
Ralph Latteck ◽  
Jorge Chau ◽  
Miguel Urco ◽  
Juha Vierinen ◽  
Victor Avsarkisov
Keyword(s):  
Large Scale ◽  
Middle Atmosphere ◽  
Multiple Input Multiple Output ◽  
Horizontal Resolution ◽  
Neutral Wind ◽  
Stratified Turbulence ◽  
Turbulent Dissipation ◽  
Radar Echoes ◽  
Multiple Input ◽  
Input Multiple Output

<p>Atmospheric structures due to gravity waves, turbulence, Kelvin Helmholtz instabilities, etc. in the mesosphere are being studied with a varying of ground-based and satellite-based instruments. At scales less than 100 km, they are mainly studied with airglow imagers, lidars, and radars. Typical radar observations have not been able to resolve spatial and temporal ambiguities due to the strength of radar echoes, the size of the system, and/or the nature of the atmospheric irregularities. In this work we observed spatially and temporally resolved structures of PMSE with unprecedented horizontal resolution, using the improved radar imaging accuracy of the Middle Atmosphere Alomar Radar System (MAARSY) with the aid of a multiple-input multiple output (MIMO) technique. The studies are performed in both the brightness of the mesospheric echoes and their Doppler velocities. The resolutions achieved are less than 1 km in the horizontal direction, less than 300m in altitude, and less than 1 minute in time, in an area of ~15km x 15km around 85km of altitude. We present a couple of wavelike monochromatic events, one drifting with the background neutral wind, and one propagating against the neutral wind. Horizontal wavelengths, periods, and vertical and temporal coverage of the events are described and discussed. A theory of stratified turbulence is employed in the present study. In particular, it is shown that the structure that propagates with the background wind is a large-scale turbulent KHI event.  Some important turbulence characteristics, such as a turbulent dissipation rate, buoyancy Reynolds number, and Froude number, support our conclusion.</p>

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