Subjects: Geosciences >> Space Physics submitted time 2017-01-22
Abstract： Microwave interferometer is an efficient tool for non-intrusively diagnosis of electron density of plasma, which can be used for the measurement of plume of helicon plasma thruster. Four different numerical Abel inversion algorithms, including the discretization method, the cubic spline interpolation method, the Hankel-Fourier transform method and the Nestor-Olsen method, are used to retrieved the plume density profile that is detected by microwave interferometry for the cases with and without noise. After analysis of the effect of sampling density on the retrieval error, the smoothing and interpolating solution is proposed to mitigate the under-sampling related problem. As a summary, the procedures of the retrieval and processing are proposed. Two principle verification experiments with microwave network analyzer have been done. In the first experiment, a circular pipe is measured as a axial symmetrical target, which simulates the plume, and the retrieval results match well with the shape of the pipe. In the second experiment, spatial resolved integrated phase shifts are retrieved by Abel algorithm. The radial electron density profile within the plume is calculated. The experiments and their results verify the performance and validity of both the system design and the retrieval algorithm.
Peer Review Status:
Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： High-resolution reconstruction techniques are investigated for Hai Yang-2Scatterometer(HY2-SCAT)backscatter measurements for a variety of application purposes including land and polar ice detection and the studies of cryophere and biosphere.Three resolution enhancement algorithms,including Additive Algebraic Reconstruction Technique (AART),Multiplicative Algebraic Reconstruction Technique(MART)and Scatterometer Image Reconstruction(SIR),are compared by simulation approach.The results that SIR has the best performance in noise suppression and resolution enhancement of the backscatter measurements than AART and MART algorithms.This study is verified using HY2-SCAT Level-1B(L1B)backscatter measurements.The sigma~0 measurements over some sites with particular backscattering characteristics(e.g.islands)are reconstructed.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： The scatterometer onboard Haiyang-2 satellite (HY-2 SCAT) is a rotating pencil-beam scatteromter. It provides 4 times of radar cross-section (sigma0) measurements at different azimuth/incidence angles over a wind vector cell, in order to determine the near-surface wind field using the Geophysical Model Function (GMF). To achieve the required wind vector accuracy, radar cross-section measurements must be calibrated within a few tenths of a decibel (within 0.5 dB). In this paper, HY-2 SCAT is calibrated using natural land-extended targets over different regions and is compared with OSCAT. sigma~0 errors over different azimuth angles are eliminated. The error sources of the measurements are analyzed and the pointing errors are compared with that estimated from measurements of Altimeter onboard HY-2 satellite.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics Subjects: Geosciences >> Marine Sciences submitted time 2016-05-03
Abstract： In order to study the feasibility of ocean surface current measurement using radar scatterometer, the system parameters of the traditional scatterometer were modified, the coherent coefficient model and decorrelation factors were derived, and the phase error model was obtained. Moreover, this paper established an end-to-end model to simulate the ocean surface current measurement. The input wind speeds ranged from 2m/s to 21m/s and the wind direction was parallel to the cross track direction. The results show that the current speed standard deviation in along-track and cross-track direction are smaller than 0.1m/s, when the wind speed is greater than 5m/s. And the swath that can be used for current speed inversion is greater than 40%, when the wind speed is larger than 7m/s. The width of effective swath increases with the increase of the wind speeds. After parameters' optimization, communication error was calculated and the results show that the communication error of the modified scatterometer is better than that of the fan-beam, rotating scatterometer in both the low wind speed and high wind speed conditons. � 2015, Chinese Institute of Electronics. All right reserved.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-03
Abstract： The scatterometer onboard HY-2 satellite is calibrated using Numerical Ocean Calibration and its retrieval winds after calibration are validated from 130 global buoys and winds from the European Centre for Medium-Range Weather Foresting Numerical Weather Prediction model using triple-collocation during December 2012, resulting in 3112 collocated triplets. The KNMI QC flag is used to collocate the data without rain efforts. It is found that functional relationship employing the error-in-variables method is more accuracy than that using linear regression for the validation of retrieval wind from HY-2 scatterometer. Moreover, using the wind component domain is confirmed to be favourable. It is shown that the uncertainties after ocean calibration is less than 0.15dB, resulting in 0.2m/s systematic wind effects. For both zonal and meridional winds, the similar wind fields comparing with buoys and ECMWF indicate that the effective of the calibration and high quality of the retrieval winds. �2015, Chinese Institute of Electronics. All right reserved.
Peer Review Status:Awaiting Review
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