On-Ground Retracking to Correct Distorted Waveform in Spaceborne Global Navigation Satellite System-Reflectometry
Spaceborne Global Navigation Satellite System-Reflectometry (GNSS-R) has been the research focus of Earth observation because of its unique advantages; however, there are still many challenges to be resolved. The reduction of the impact of the satellite motion on the GNSS-R waveform is the one of ke...
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| Format: | Article |
| Language: | English |
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MDPI AG
2017-06-01
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| Series: | Remote Sensing |
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| Online Access: | http://www.mdpi.com/2072-4292/9/7/643 |
| _version_ | 1819290882870870016 |
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| author | Feng Wang Dongkai Yang Weiqiang Li Wei Yang |
| author_facet | Feng Wang Dongkai Yang Weiqiang Li Wei Yang |
| author_sort | Feng Wang |
| collection | DOAJ |
| description | Spaceborne Global Navigation Satellite System-Reflectometry (GNSS-R) has been the research focus of Earth observation because of its unique advantages; however, there are still many challenges to be resolved. The reduction of the impact of the satellite motion on the GNSS-R waveform is the one of key technologies for spaceborne GNSS-R. The proposed delay retracking methods in existing literatures require too many instrument resources and too much priori information to refresh correlation window on each coherent integration time period. This paper aims to propose an on-ground alternative in which less frequency tracking refresh on board is needed. The model of dynamic delay waveform, which is expressed as the convolution of the pure waveform and the point spread function, are described. Based on this, the new methodology, which utilizes the least squares fitting to make the residual error between the dynamic model and measured waveform minimum, is employed to reconstruct the pure waveform. The validity of proposed method is verified using UK-DMC, UK-TDS-1 and simulated data. Moreover, the performances of sea surface height and wind speed retrieval using retracked and non-retracked waveforms are compared. The results show that (1) the MSEs between aligned and retracked waveform reduce to 0.026 and 0.044 from 0.110 and 0.156 between aligned and non-retracked waveform with the TRP of 1 s and 3 s for UK-DMC data, and for UK-TDS-1 data, the MSEs decrease from 161.02 and 227.34 to 70.10 and 61.80; (2) the standard deviation of sea surface height using retracked waveform is lower 5 times than the one using non-retracked waveform; (3) the retracked waveform could lead to a better measurement performance in wind speed retrieval. Finally, the relationship between the performance of retracking and Signal-to-Noise Ratio (SNR) is analyzed. The results show that when the SNR of the waveform is lower than 3 dB, the retrieval accuracies rapidly become worse. |
| first_indexed | 2024-12-24T03:29:49Z |
| format | Article |
| id | doaj.art-d43901d98dfc48cd8722f6aa935c2578 |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-12-24T03:29:49Z |
| publishDate | 2017-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-d43901d98dfc48cd8722f6aa935c25782022-12-21T17:17:15ZengMDPI AGRemote Sensing2072-42922017-06-019764310.3390/rs9070643rs9070643On-Ground Retracking to Correct Distorted Waveform in Spaceborne Global Navigation Satellite System-ReflectometryFeng Wang0Dongkai Yang1Weiqiang Li2Wei Yang3School of Electronic and Information Engineering, Beihang University, Beijing, 100191 ChinaSchool of Electronic and Information Engineering, Beihang University, Beijing, 100191 ChinaEarth Observation Researth Group, Institu d’Estudis Espacials de Catalunya (ICE-CSIC/IEEC), 08191 Barcelona, SpainSchool of Electronic and Information Engineering, Beihang University, Beijing, 100191 ChinaSpaceborne Global Navigation Satellite System-Reflectometry (GNSS-R) has been the research focus of Earth observation because of its unique advantages; however, there are still many challenges to be resolved. The reduction of the impact of the satellite motion on the GNSS-R waveform is the one of key technologies for spaceborne GNSS-R. The proposed delay retracking methods in existing literatures require too many instrument resources and too much priori information to refresh correlation window on each coherent integration time period. This paper aims to propose an on-ground alternative in which less frequency tracking refresh on board is needed. The model of dynamic delay waveform, which is expressed as the convolution of the pure waveform and the point spread function, are described. Based on this, the new methodology, which utilizes the least squares fitting to make the residual error between the dynamic model and measured waveform minimum, is employed to reconstruct the pure waveform. The validity of proposed method is verified using UK-DMC, UK-TDS-1 and simulated data. Moreover, the performances of sea surface height and wind speed retrieval using retracked and non-retracked waveforms are compared. The results show that (1) the MSEs between aligned and retracked waveform reduce to 0.026 and 0.044 from 0.110 and 0.156 between aligned and non-retracked waveform with the TRP of 1 s and 3 s for UK-DMC data, and for UK-TDS-1 data, the MSEs decrease from 161.02 and 227.34 to 70.10 and 61.80; (2) the standard deviation of sea surface height using retracked waveform is lower 5 times than the one using non-retracked waveform; (3) the retracked waveform could lead to a better measurement performance in wind speed retrieval. Finally, the relationship between the performance of retracking and Signal-to-Noise Ratio (SNR) is analyzed. The results show that when the SNR of the waveform is lower than 3 dB, the retrieval accuracies rapidly become worse.http://www.mdpi.com/2072-4292/9/7/643delay waveformretrackingspaceborneGlobal Navigation Satellite System-Reflectometry (GNSS-R) |
| spellingShingle | Feng Wang Dongkai Yang Weiqiang Li Wei Yang On-Ground Retracking to Correct Distorted Waveform in Spaceborne Global Navigation Satellite System-Reflectometry Remote Sensing delay waveform retracking spaceborne Global Navigation Satellite System-Reflectometry (GNSS-R) |
| title | On-Ground Retracking to Correct Distorted Waveform in Spaceborne Global Navigation Satellite System-Reflectometry |
| title_full | On-Ground Retracking to Correct Distorted Waveform in Spaceborne Global Navigation Satellite System-Reflectometry |
| title_fullStr | On-Ground Retracking to Correct Distorted Waveform in Spaceborne Global Navigation Satellite System-Reflectometry |
| title_full_unstemmed | On-Ground Retracking to Correct Distorted Waveform in Spaceborne Global Navigation Satellite System-Reflectometry |
| title_short | On-Ground Retracking to Correct Distorted Waveform in Spaceborne Global Navigation Satellite System-Reflectometry |
| title_sort | on ground retracking to correct distorted waveform in spaceborne global navigation satellite system reflectometry |
| topic | delay waveform retracking spaceborne Global Navigation Satellite System-Reflectometry (GNSS-R) |
| url | http://www.mdpi.com/2072-4292/9/7/643 |
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