{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T04:12:46Z","timestamp":1760242366127,"version":"build-2065373602"},"reference-count":34,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2017,6,22]],"date-time":"2017-06-22T00:00:00Z","timestamp":1498089600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>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.<\/jats:p>","DOI":"10.3390\/rs9070643","type":"journal-article","created":{"date-parts":[[2017,6,22]],"date-time":"2017-06-22T10:11:35Z","timestamp":1498126295000},"page":"643","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["On-Ground Retracking to Correct Distorted Waveform in Spaceborne Global Navigation Satellite System-Reflectometry"],"prefix":"10.3390","volume":"9","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9046-3388","authenticated-orcid":false,"given":"Feng","family":"Wang","sequence":"first","affiliation":[{"name":"School of Electronic and Information Engineering, Beihang University, Beijing 100191, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dongkai","family":"Yang","sequence":"additional","affiliation":[{"name":"School of Electronic and Information Engineering, Beihang University, Beijing 100191, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Weiqiang","family":"Li","sequence":"additional","affiliation":[{"name":"Earth Observation Researth Group, Institu d\u2019Estudis Espacials de Catalunya (ICE-CSIC\/IEEC), 08191 Barcelona, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wei","family":"Yang","sequence":"additional","affiliation":[{"name":"School of Electronic and Information Engineering, Beihang University, Beijing 100191, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2017,6,22]]},"reference":[{"key":"ref_1","first-page":"331","article-title":"A passive reflectometry and interferometry system (PARIS): Applocation to ocean altimetry","volume":"17","year":"1993","journal-title":"Ecol. Soc. Am. J."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1029\/2000RS002539","article-title":"First spaceborne observation of an Earth-reflected GPS signal","volume":"37","author":"Lowe","year":"2002","journal-title":"Radio Sci."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1229","DOI":"10.1109\/TGRS.2005.845643","article-title":"Detection and processing of bistatically reflected GPS signlas from low Earth orbit for the purpose of ocean remote sensing","volume":"43","author":"Gleason","year":"2005","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_4","unstructured":"Unwin, M., Duncan, S., Jales, P., Blunt, P., and Brenchley, M. (2014, January 8\u201312). Implementing GNSS reflectometry in space on the TechDemoSat-1 misson. Proceedings of the 27th International Technical Meeting of The Satellite Division of the Institute of Navigation, Tampa, FL, USA."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"5435","DOI":"10.1002\/2015GL064204","article-title":"Spcaeboren GNSS reflectometry for ocean winds: First results from the UK TechDemoSat-1 mission","volume":"42","author":"Foti","year":"2015","journal-title":"Geophys. Res. Lett."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Ruf, C.S., Gleason, S., Jelenak, Z., Katzberg, S., Ridley, A., Rose, R., Scherrer, J., and Zavorotny, V. (2012, January 22\u201327). The CYGNSS nanosatellite constellation hurricane mission. Proceedings of the 2012 IEEE International Geoscience and Remote Sensing Symposium, Munich, Germany.","DOI":"10.1109\/IGARSS.2012.6351600"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"6829","DOI":"10.1109\/TGRS.2014.2303831","article-title":"Spaceborne GNSS-R minimum variance wind speed estimator","volume":"52","author":"Clarizia","year":"2014","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"4419","DOI":"10.1109\/TGRS.2016.2541343","article-title":"Wind speed retrieval algorithm for the Cyclone Global Navigation Satellite System (CYGNSS) mission","volume":"54","author":"Clarizia","year":"2016","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1142","DOI":"10.1109\/TGRS.2015.2475317","article-title":"Generalized linear observables for ocean wind retrieval from calibrated GNSS-R delay-Doppler maps","volume":"54","author":"Rodriguez","year":"2016","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"4678","DOI":"10.1109\/JSTARS.2016.2602703","article-title":"The GNSS reflectometry response to the ocean surface winds and waves","volume":"9","author":"Soisuvarn","year":"2016","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"767","DOI":"10.1002\/2015GL066624","article-title":"First spaceborne observation of sea surface height using GPS-reflectometry","volume":"43","author":"Clarizia","year":"2016","journal-title":"Geophys. Res. Lett."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"3317","DOI":"10.1002\/2016GL068189","article-title":"Demonstrating soil moisture remote sensing with observation from the UK TechDemoSat-1 satelllite mission","volume":"43","author":"Chew","year":"2016","journal-title":"Geophys. Res. Lett."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"4730","DOI":"10.1109\/JSTARS.2016.2588467","article-title":"Sensitivity of GNSS-R spaceborne observations to soil miosture and vegetation","volume":"9","author":"Camps","year":"2016","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Hu, C., Benson, C., Rizos, C., and Li, Q. (2017). Single-pass sub-meter space-based GNSS-R ice altimetry: Results from TDS-1. IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens.","DOI":"10.1109\/JSTARS.2017.2690917"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Yan, Q., Huang, W., and Moloney, C. (2017). Neural networks based sea ice detection and concentration retrieval from GNSS-R delay-Doppler maps. IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens.","DOI":"10.1109\/JSTARS.2017.2689009"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"734","DOI":"10.1109\/LGRS.2017.2676823","article-title":"Observing sea\/ice transition using radar images generated from TechDemoSat-1 delay Doppler maps","volume":"13","author":"Schiavulli","year":"2017","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1573","DOI":"10.1109\/JSTARS.2014.2301019","article-title":"Reconstruction of the normalized radar cross section field from GNSS-R delay-Doppler map","volume":"7","author":"Schiavulli","year":"2014","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"750","DOI":"10.1109\/LGRS.2011.2107500","article-title":"Ocean surface\u2019s scattering coefficient retrieval by delay-Doppler map inversion","volume":"8","author":"Valencia","year":"2011","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"4669","DOI":"10.1109\/JSTARS.2016.2542348","article-title":"The first application of stare processing to retrieve mean square slope using the SGE-ReSI GNSS-R experimenntal on TDS-1","volume":"9","author":"Tye","year":"2016","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Gleason, S. (2006). Remote Sensing of Ocean, Ice and Land Surfaces Using Bistatically Scattered GNSS Signals from Low Earth Orbit. [Ph.D. Thesis, University Surrey].","DOI":"10.1109\/IGARSS.2006.792"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"507","DOI":"10.1007\/s10291-011-0251-7","article-title":"Retracking considerations in soaceborne GNSS-R altimetry","volume":"16","author":"Park","year":"2012","journal-title":"GPS Solut."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1481","DOI":"10.1109\/JSTARS.2014.2322198","article-title":"Analysis of spaceborne GNSS-R delay-Doppler tracking","volume":"7","author":"Park","year":"2014","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1109\/LGRS.2012.2192255","article-title":"Delay tracking in spaceborne GNSS-R ocean altimetry","volume":"10","author":"Park","year":"2013","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"951","DOI":"10.1109\/36.841977","article-title":"Scattering of GPS signals from the ocean with wind remote sensing application","volume":"38","author":"Zavorotny","year":"2000","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"15781","DOI":"10.1029\/97JC00467","article-title":"A unified directional spectrum for long and short wind-driven waves","volume":"102","author":"Elfouhaily","year":"1997","journal-title":"J. Geophys. Res."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"839","DOI":"10.1109\/JOE.2007.903985","article-title":"A physically consistent speckle model for Marine SLC SAR images","volume":"32","author":"Migliaccio","year":"2007","journal-title":"IEEE J. Ocean. Eng."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1145","DOI":"10.1364\/JOSA.66.001145","article-title":"Some fundamental properties of speckle","volume":"66","author":"Goodman","year":"1976","journal-title":"J. Opt. Soc. Am."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"208","DOI":"10.1016\/j.asr.2010.03.023","article-title":"Fading statistics and sensing accuracy of ocean scattered GNSS and altimetry signals","volume":"46","author":"Gleason","year":"2010","journal-title":"Adv. Space Res."},{"key":"ref_29","unstructured":"Ulaby, F.T., Moore, R.K., and Fung, A.K. (1982). Microwave Remote Sensing: Active and Passive, Volume II: Radar Remote Sensing and Surface Scattering and Emissition Theory, Artech House."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1493","DOI":"10.1109\/JSTARS.2014.2320298","article-title":"Experimental evaluation of GNSS-Reflectometry altimetric precison using P(Y) and C\/A signals","volume":"7","author":"Csmps","year":"2014","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"4660","DOI":"10.1109\/JSTARS.2016.2537698","article-title":"An assessment of the precision and accuracy of altimetry retrievals for a monterey bay GNSS-R experiment","volume":"9","author":"Mashburn","year":"2016","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"421","DOI":"10.1007\/s00190-005-0485-7","article-title":"Geometry and accuracy of reflecting points in bistatic satellite altimetry","volume":"79","author":"Wangner","year":"2005","journal-title":"J. Geod."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"4853","DOI":"10.1109\/TGRS.2012.2230401","article-title":"Spaceborne-based GNSS scatterometry: Ocean wind sensing using an empirically calibrated model","volume":"51","author":"Gleason","year":"2013","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Haupt, S.E., Pasini, A., and Marzban, C. (2009). Artificial Intelligent Methods in the Environmental Sciences, Springer.","DOI":"10.1007\/978-1-4020-9119-3"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/9\/7\/643\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:40:01Z","timestamp":1760208001000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/9\/7\/643"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,6,22]]},"references-count":34,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2017,7]]}},"alternative-id":["rs9070643"],"URL":"https:\/\/doi.org\/10.3390\/rs9070643","relation":{},"ISSN":["2072-4292"],"issn-type":[{"type":"electronic","value":"2072-4292"}],"subject":[],"published":{"date-parts":[[2017,6,22]]}}}