Browse Articles
Simulation and Observational Evaluation of Space Debris Detection by Sanya Incoherent Scatter Radar
-  29 September 2022
Key Points
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Simulation and experiments to evaluate space debris detection performance based on newly built Sanya incoherent scatter radar (SYISR) have been performed
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The estimated radar cross section versus range of typical space debris accord well with the theoretical curve
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The detectable lower limit size of space debris is ∼8 cm in a range of 1,000 km without integration based on SYISR
Meteor Detection With a New Computer Vision Approach
-  29 September 2022
Key Points
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A highly capable meteor head echo detection algorithm is developed
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Introducing the complete automatic package of meteor detection with computer vision and deep learning
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Meteors with higher Signal-to-Noise Ratio are detected in a slightly lower range and with a lower radial velocity
Radar—CubeSat Transionospheric HF Propagation Observations: Suomi 100 Satellite and EISCAT HF Facility
-  20 September 2022
Key Points
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Active radar-satellite transionospheric measurements in the high frequency (HF) range with a CubeSat-size satellite have been performed
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A radio spectrometer onboard the Suomi 100 CubeSat detected a clear signal transmitted by the EISCAT HF heater
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The properties of ionospheric plasma were found to be affected by the energy of the transmitted heater signal
Deriving Ionospheric Total Electron Content by VLBI Global Observing System Data Analysis During the CONT17 Campaign
-  15 September 2022
Key Points
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We studied the variation of ionospheric total electron content over six sites as determined using data of the new geodetic very long baseline interferometry (VLBI) system, VLBI global observing system (VGOS), in December 2017
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By enhancing the model, we estimated the temporal variation of the latitudinal ionosphere gradient and achieved more accurate results
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We compared our results with global navigation satellite system vertical total electron content which enabled us to detect an error in the sign of the VGOS differential total electron content calculation
Manx Arrays: Perfect Non-Redundant Interferometric Geometries
-  9 September 2022
Key Points
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A “perfect array” is a mathematical construct with uniform and complete element spacings to a circle of radius up to the maximum uv-distance
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The Manx array represents the configuration of the largest perfect array
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Fractal replication of the Manx array results in uv-efficient layouts
Seasonal and Diurnal Dynamics of Radio Noise for 8–20 MHz Poleward-Oriented Mid-Latitude Radars
-  31 August 2022
Key Points
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Physics-based seasonal-daily noise level model built for pole-oriented high-frequency radars
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Good agreement between modeled noise level and experimental observations
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Model allows estimating vertical absorption from noise measurements at these radars
An Improved Method of Surface Clutter Simulation Based on Orbiting Radar in Tianwen-1 Mars Exploration
-  31 August 2022
Key Points
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Wavelength-scale surface roughness is introduced into the proposed surface clutter simulation method
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The proposed surface clutter simulation method is applied to verify the ionospheric error correction approach
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Echo peak power simulated by the proposed method is in good agreement with MRO SHARAD radargram
A Calibration Method of Short-Time Waveform Signals Passed Through Linear Time-Invariant Systems: 1. Methodology and Simple Examples
-  24 August 2022
Key Points
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We propose a calibration method using short-time Fourier transform (STFT) for waveform data, such as plasma waves observed in space
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The accuracy of the method is evaluated using the transfer functions of well-known filters and frequency-fixed sinusoidal waveforms
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The proposed method provides the most accurately calibrated data compared with conventional methods using STFT
A Technique for the Array Partitioning
-  3 October 2022
Key Points
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The presented method determines the optimal partitioning of an aperture into sub-apertures fed with a constant phase
Radio Refractive Index of Wet Atmosphere Estimated from Site Test Interferometer Data
-  29 September 2022
Key Points
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Refractive index structure constants were derived from Site Test Interferometer (STI) phase delay scatter for a variety of climates
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The strongest diurnal variation in this parameter occurred for the high-desert site at Goldstone, California
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We found good correlation with the derived STI structure parameters and a model which included planetary boundary layer height
Satellite radar interferometry: Two-dimensional phase unwrapping
- Radio Science
-  713-720
-  July-August 1988
A global mapping technique for GPS-derived ionospheric total electron content measurements
- Radio Science
-  565-582
-  1 May 1998
Geodesy by radio interferometry: Effects of atmospheric modeling errors on estimates of baseline length
- Radio Science
-  1593-1607
-  November-December 1985
Singular value decomposition methods for wave propagation analysis
- Radio Science
-  12 February 2003
Estimation of tropospheric delay for microwaves from surface weather data
- Radio Science
-  379-386
-  May-June 1987
Statistics of total electron content depletions observed over the South American continent for the year 2008
- Radio Science
-  29 October 2011
Key Points
- First time regional plots of TEC depletions
- New numerical algorithm developed to automatically detect TEC depletions
- Day-to-day variability of TEC depletions in a regional basis
AIM: Adaptive integral method for solving large-scale electromagnetic scattering and radiation problems
- Radio Science
-  1225-1251
-  1 September 1996
Ionospheric constraints on VHF/UHF communications links during solar maximum and minimum periods
- Radio Science
-  363-378
-  May-June 1988
An Indoor Path Loss Prediction Model Using Wall Correction Factors for Wireless Local Area Network and 5G Indoor Networks
- Radio Science
-  544-564
-  2 April 2018
Key Points
- A modified effective wall loss model (EWLM) for indoor environment is presented
- Real-time measurements and simulations for various indoor path loss models are used
- Several frequency spectrum band were considered for evaluation purposes
Accurate measurements of the dielectric constant of seawater at L band
- Radio Science
-  2-24
-  2 December 2015
Key Points
- Dielectric measurements of seawater are made with a microwave cavity at 1.413 GHz
- Measurements are made as a function of temperature and salinity for values found in open ocean
- Accuracy is better than 0.3 for both real and imaginary parts of the dielectric constant
Measurement of Ionospheric Total Electron Content Using Single-Frequency Geostationary Satellite Observations
- Radio Science
-  10-19
-  24 October 2018
Key Points
- The derivation of total electron content using single-frequency terrestrial GPS receivers and geostationary satellites is demonstrated
- The demonstrated technique is validated by correlation analysis
- The correlations between TEC time series for pairs of receivers and between receivers and an ionosonde over a year show good agreement
Plain Language Summary
The ionized upper portion of the atmosphere is known as the ionosphere. The ionosphere interferes with signals traveling between satellites and the ground and can cause errors in satellite navigation, surveillance, and communication systems. The impact of these errors can be reduced if we are able to measure the total electron content (TEC), which can be simply thought of as the total number of electrons in a straight line between a satellite and the ground. We have developed a technique that allows us to measure TEC using receivers measuring single-frequency signals from geostationary satellites. This is useful because it will increase the number of measurements available and because using geostationary satellites makes the measurements relatively easy to interpret. To test the technique we use a correlation analysis to compare measurements made by the single-frequency receivers. We also correlate technique measurements with independent TEC observations made by an ionosonde. All correlation results showed good agreement, suggesting consistency for the technique, and that the technique is reliable. The demonstrated technique has the potential to become a routine method to derive TEC, which will help to map the ionosphere in real time.
Software-Defined Radio Decoding of DCF77: Time and Frequency Dissemination with a Sound Card
- Radio Science
-  48-61
-  14 December 2017
Key Points
- DCF77 signals are used for time of flight measurement using Software-defined radio processing
- A 10 μs resolution time measurement and sub-ppm frequency resolution with a sound card are demonstrated
- Ionospheric delay characterization for educational purposes and long-term instigation with low-cost equipment has been developed
Plain Language Summary
Software-defined radio aims at reducing to its minimum the hardware setup needed to process radio frequency signals and relies on software processing for demodulation: here we demonstrate the precise measurement of an atomic clock-locked emitter, propagating at very low frequency, using only a general purpose computer sound card. Thanks to the high accuracy of the time of flight accessible through an improved modulation schemes, such physical properties as ionosphere altitude and ground wave versus air wave are detected. The frequency of the atomic clock is compared with the sound card local oscillator frequency, demonstrating the temperature dependence of the latter, readily measured in this experiment.
Calculating the absorption of HF radio waves in the ionosphere
- Radio Science
-  767-783
-  5 June 2017
Key Points
- Either the Appleton-Hartree or Sen Wyller dispersion relation can be used to calculate absorption
- It is necessary to utilize the correct collision frequency specification for each dispersion relation
- Geophysical variations of collision frequency should be included in absorption calculations
Radio wave propagation through vegetation: Factors influencing signal attenuation
- Radio Science
-  7 October 2003
Fresnel Reflection and Transmission Coefficients for Temporally Dispersive Attenuative Media
- Radio Science
-  1382-1397
-  27 October 2018
Key Points
- General expressions for Fresnel reflection and transmission coefficients for homogeneous and inhomogeneous plane waves are derived for TE- and TM polarized plane waves in complex media with loss
- The critical angle for total internal reflection remains unchanged when material loss is included; the polarizing angle (for a TM polarized plane wave is changed otherwise, a pseudo Brewster's angle occurs at which the magnitude of the TM) polarization reflection coefficient is a minimum
- Total reflection at grazing incidence on the optically denser medium does not occur when both media exhibit loss; total reflection does not occur at critical incidence when both media exhibit loss.
Plain Language Summary
Amplitude reflection and transmission coefficients for a time-harmonic electromagnetic plane wave incident upon a plane interface separating two different lossy media are developed.
Synopsis of the historical development of Schumann resonances
- Radio Science
-  28 March 2007
Large ionospheric disturbances produced by the HAARP HF facility
- Radio Science
-  1081-1093
-  4 June 2016
Key Points
- HAARP facility produces unique results
- Artificial plasma clouds are emission and optical signatures
- Future HAARP experiments are needed to explain physics