{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2024,4,8]],"date-time":"2024-04-08T08:35:34Z","timestamp":1712565334703},"reference-count":24,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2024,3,21]],"date-time":"2024-03-21T00:00:00Z","timestamp":1710979200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"EU"},{"DOI":"10.13039\/501100000844","name":"ESA","doi-asserted-by":"publisher","award":["4000134346\/21\/NL\/AD"],"id":[{"id":"10.13039\/501100000844","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"In this study, the full-focusing (FF) algorithm is reviewed with the objective of optimizing it for processing data from different types of surfaces probed in altimetry. In particular, this work aims to provide a set of optimal FF processing parameters for the Sentinel-6 Michael Freilich (S6-MF) mission. The S6-MF satellite carries an advanced radar altimeter offering a wide range of potential FF-based applications which are just beginning to be explored and require prior optimization of this processing. In S6-MF, the Synthetic Aperture Radar (SAR) altimeter acquisitions are known to be aliased in the along-track direction. Depending on the target, aliasing can be tolerated or may be a severe impairment to provide the level of performance expected from FF processing. Another key aspect to consider in this optimization study is the unprecedented resolution of the FF processing, which results in a higher posting rate than the standard SAR processing. This work investigates the relationship between posting rate and noise levels and provides recommendations for optimal algorithm configurations in various scenarios, including transponder, open ocean, and specular targets like sea-ice and inland water scenes. The Omega\u2013Kappa (WK) algorithm, which has demonstrated superior CPU efficiency compared to the back-projection (BP) algorithm, is considered for this study. But, unlike BP, it operates in the Doppler frequency domain, necessitating further precise spectral and time domain settings. Based on the results of this work, real case studies using S6-MF acquisitions are presented. We first compare S6-MF FF radargrams with Sentinel-1 (S1) images to showcase the potential of optimally configured FF processing. For highly specular surfaces such as sea-ice, distinct techniques are employed for lead signature identification. S1 relies on image-based lineic reconstruction, while S6-MF utilizes phase coherency of focalized pulses for lead detection. The study also delves into two-dimensional wave spectra derived from the amplitude modulation of image\/radargrams, with a focus on a coastal example. This case is especially intriguing, as it vividly illustrates different sea states characterized by varying spectral peak positions over time.<\/jats:p>","DOI":"10.3390\/rs16061112","type":"journal-article","created":{"date-parts":[[2024,3,22]],"date-time":"2024-03-22T09:10:53Z","timestamp":1711098653000},"page":"1112","source":"Crossref","is-referenced-by-count":1,"title":["Optimal Configuration of Omega-Kappa FF-SAR Processing for Specular and Non-Specular Targets in Altimetric Data: The Sentinel-6 Michael Freilich Study Case"],"prefix":"10.3390","volume":"16","author":[{"given":"Samira","family":"Amraoui","sequence":"first","affiliation":[{"name":"Collecte Localisation Satellites, 31520 Ramonville-Saint-Agne, France"}]},{"ORCID":"http:\/\/orcid.org\/0000-0002-7126-0040","authenticated-orcid":false,"given":"Pietro","family":"Guccione","sequence":"additional","affiliation":[{"name":"ARESYS SRL, 20132 Milan, Italy"}]},{"given":"Thomas","family":"Moreau","sequence":"additional","affiliation":[{"name":"Collecte Localisation Satellites, 31520 Ramonville-Saint-Agne, France"}]},{"given":"Marta","family":"Alves","sequence":"additional","affiliation":[{"name":"Collecte Localisation Satellites, 31520 Ramonville-Saint-Agne, France"}]},{"ORCID":"http:\/\/orcid.org\/0000-0002-3868-0676","authenticated-orcid":false,"given":"Ourania","family":"Altiparmaki","sequence":"additional","affiliation":[{"name":"Astrodynamics and Space Missions, Aerospace Engineering, Delft University of Technology, 2629 HS Delft, The Netherlands"}]},{"given":"Charles","family":"Peureux","sequence":"additional","affiliation":[{"name":"Collecte Localisation Satellites, 31520 Ramonville-Saint-Agne, France"}]},{"given":"Lisa","family":"Recchia","sequence":"additional","affiliation":[{"name":"ARESYS SRL, 20132 Milan, Italy"}]},{"given":"Claire","family":"Maraldi","sequence":"additional","affiliation":[{"name":"Centre National d\u2019\u00c9tudes Spatiales, 31400 Toulouse, France"}]},{"ORCID":"http:\/\/orcid.org\/0000-0003-1925-1558","authenticated-orcid":false,"given":"Fran\u00e7ois","family":"Boy","sequence":"additional","affiliation":[{"name":"Centre National d\u2019\u00c9tudes Spatiales, 31400 Toulouse, France"}]},{"given":"Craig","family":"Donlon","sequence":"additional","affiliation":[{"name":"European Space Agency, ESTEC\/EOP-SME, 2201 AZ Noordwijk, The Netherlands"}]}],"member":"1968","published-online":{"date-parts":[[2024,3,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"392","DOI":"10.1109\/TGRS.2016.2607122","article-title":"Fully Focused SAR Altimetry: Theory and Applications","volume":"55","author":"Egido","year":"2017","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_2","unstructured":"Amraoui, S., Moreau, T., Scagliola, M., Guccione, P., Alves, M., Boy, F., Maraldi, C., Picot, N., and Donlon, C. (2022, January 6\u201316). Lead detection method from Sentinel-6 FF-SAR combined with imagery data, Living Planet Symposium (LPS). Proceedings of the Meeting in Bonn, Bonn, Germany."},{"key":"ref_3","unstructured":"Egido, A., Buchhaupt, C., Donghui, Y., Smith, W.H.F., Zhang, D., and Connor, L. (2022, January 6\u201316). A Novel Physical Retracker for Sea-Ice Freeboard Determination from High Resolution SAR Altimetry, Living Planet Symposium (LPS). Proceedings of the Meeting in Bonn, Bonn, Germany."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Gibert, F., G\u00f3mez-Oliv\u00e9, A., McKeown, C., Molina, R., and Garcia-Mond\u00e9jar, A. (2022, January 27\u201328). Water Elevation and Water Extent Measurements With Sentinel-6 Fully-Focussed SAR, Ocean Surface Topography Science Team (OSTST). Proceedings of the Meeting in Venice, Venice, Italy.","DOI":"10.5194\/egusphere-egu23-448"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"113517","DOI":"10.1016\/j.rse.2023.113517","article-title":"Benefits of fully focused SAR altimetry to coastal wave height estimates: A case study in the North Sea","volume":"289","author":"Schlembach","year":"2023","journal-title":"Remote Sens. Environ."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"e2021GL096224","DOI":"10.1029\/2021GL096224","article-title":"SAR Altimetry Data as a New Source for Swell Monitoring","volume":"49","author":"Altiparmaki","year":"2022","journal-title":"Geophys. Res. Lett."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"853","DOI":"10.1016\/j.asr.2020.07.015","article-title":"Impact of vertical water particle motions on focused SAR altimetry","volume":"68","author":"Buchhaupt","year":"2021","journal-title":"Adv. Space Res."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Guccione, P., Scagliola, M., and Giudici, D. (2018). 2D Frequency Domain Fully Focused SAR Processing for High PRF Radar Altimeters. Remote Sens., 10.","DOI":"10.3390\/rs10121943"},{"key":"ref_9","unstructured":"Phalippou, L., Caubet, E., and Thouvenot, E. (July, January 28). A Ka-band altimeter for future altimetry missions. Proceedings of the IEEE 1999 International Geoscience and Remote Sensing Symposium, Hamburg, Germany. IGARSS\u201999 (Cat. No.99CH36293)."},{"key":"ref_10","unstructured":"Rostan, F., and Mallow, U. Proceedings of the IGARSS 2001. Scanning the Present and Resolving the Future, Proceedings of the IEEE 2001 International Geoscience and Remote Sensing Symposium (Cat. No.01CH37217)."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Donlon, C., Cullen, R., Giulicchi, L., Fornari, M., and Vuilleumier, P. (2021, January 11\u201316). Copernicus Sentinel-6 Michael Freilich Satellite Mission: Overview and Preliminary in Orbit Results. Proceedings of the 2021 IEEE International Geoscience and Remote Sensing Symposium IGARSS, Brussels, Belgium.","DOI":"10.1109\/IGARSS47720.2021.9553731"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"892","DOI":"10.1016\/j.asr.2020.06.004","article-title":"A RIP-based SAR retracker and its application in North East Atlantic with Sentinel-3","volume":"68","author":"Dinardo","year":"2021","journal-title":"Adv. Space Res."},{"key":"ref_13","unstructured":"Curlander, J.C., and McDonough, N.R. (1992). Synthetic Aperture Radar: Systems and Signal Processing, Wiley."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"911","DOI":"10.1109\/TGRS.2014.2330423","article-title":"SAR Altimeter Backscattered Waveform Model","volume":"53","author":"Ray","year":"2015","journal-title":"Geosci. Remote Sens. IEEE Trans."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1377","DOI":"10.1016\/j.asr.2022.11.034","article-title":"Validity assessment of SAMOSA retracking for fully-focused SAR altimeter waveforms","volume":"71","author":"Ehlers","year":"2023","journal-title":"Adv. Space Res."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2458","DOI":"10.1016\/j.asr.2022.07.001","article-title":"Performance evaluation of the CDN1 altimetry Cal\/Val transponder to internal and external constituents of uncertainty","volume":"70","author":"Mertikas","year":"2022","journal-title":"Adv. Space Res."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Bertero, M., and Boccacci, P. (2020). Introduction to Inverse Problems in Imaging, CRC Press.","DOI":"10.1201\/9780367806941"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"9927","DOI":"10.1109\/TGRS.2021.3064236","article-title":"Benefits of the Adaptive Algorithm for Retracking Altimeter Nadir Echoes: Results From Simulations and CFOSAT\/SWIM Observations","volume":"59","author":"Tourain","year":"2021","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"4050","DOI":"10.1109\/TGRS.2018.2889519","article-title":"Comparative Evaluation of Sea Ice Lead Detection Based on SAR Imagery and Altimeter Data","volume":"57","author":"Thibaut","year":"2019","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Rieu, P., Amraoui, S., and Restano, M. (2023, February 15). Standalone Multi-mission Altimetry Processor (SMAP), June 2021. Available online: https:\/\/github.com\/cls-obsnadir-dev\/SMAP-FFSAR.","DOI":"10.5270\/esa-cnes.sentinel-3.smap"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"167","DOI":"10.1002\/cyto.a.20022","article-title":"Design and validation of a tool for neurite tracing and analysis in fluorescence microscopy images","volume":"58","author":"Meijering","year":"2004","journal-title":"Cytom. Part A"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1016\/S1361-8415(98)80009-1","article-title":"Three-dimensional multi-scale line filter for segmentation and visualization of curvilinear structures in medical images","volume":"2","author":"Sato","year":"1998","journal-title":"Med Image Anal."},{"key":"ref_23","unstructured":"Amraoui, S., Moreau, T., Borde, F., and Boy, F. (2022, January 27\u201328). Replica removal of FFSAR data, OSTST. Proceedings of the Meeting in Venice, Venice, Italy."},{"key":"ref_24","unstructured":"Hern\u00e1ndez, S., Gibert, F., Garcia-Mond\u00e9jar, A., and Roca, M. (2022, January 27\u201328). Leads Detection with Fully-Focused SAR in Antarctica, OSTST. Proceedings of the Meeting in Venice, Venice, Italy."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/16\/6\/1112\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2024,3,22]],"date-time":"2024-03-22T10:03:29Z","timestamp":1711101809000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/16\/6\/1112"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,3,21]]},"references-count":24,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2024,3]]}},"alternative-id":["rs16061112"],"URL":"https:\/\/doi.org\/10.3390\/rs16061112","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,3,21]]}}}