{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,2,21]],"date-time":"2025-02-21T16:15:23Z","timestamp":1740154523531,"version":"3.37.3"},"reference-count":62,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2021,10,28]],"date-time":"2021-10-28T00:00:00Z","timestamp":1635379200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["41774001","41874091"],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Autonomous and Controllable Special Project for the Surveying and Mapping of China","award":["816\u2013517"]},{"name":"SDUST Research Fund","award":["2014TDJH101"]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"Haiyang-2C (HY-2C) is a dynamic, marine-monitoring satellite that was launched by China and is equipped with an onboard dual-frequency GPS receiver named HY2_Receiver, which was independently developed in China. HY-2C was successfully launched on 21 September 2020. Its precise orbit is an important factor for scientific research applications, especially for marine altimetry missions. The performance of the HY2_Receiver is assessed based on indicators such as the multipath effect, ionospheric delay, cycle slip and data utilization, and assessments have suggested that the receiver can be used in precise orbit determination (POD) missions involving low-Earth-orbit (LEO) satellites. In this study, satellite-borne GPS data are used for POD with a reduced-dynamic (RD) method. Phase centre offset (PCO) and phase centre variation (PCV) models of the GPS antenna are established during POD, and their influence on the accuracy of orbit determination is analysed. After using the PCO and PCV models in POD, the root mean square (RMS) of the carrier-phase residuals is around 0.008 m and the orbit overlap validation accuracy in each direction reaches approximately 0.01 m. Compared with the precise science orbit (PSO) provided by the Centre National d\u2019Etudes Spatiales (CNES), the RD orbit accuracy of HY-2C in the radial (R) direction reaches 0.01 m. The accuracy of satellite laser ranging (SLR) range validation is better than 0.03 m. Additionally, a new method is proposed to verify the accuracy of the RD orbit of HY-2C by using space-borne Doppler orbitography and radiopositioning integrated by satellite (DORIS) data directly. DORIS data are directly compared to the result calculated using the accurate coordinates of beacons and the RD orbit, and the results indicate that the external validation of HY-2C RD orbit has a range rate accuracy of within 0.0063 m\/s.<\/jats:p>","DOI":"10.3390\/rs13214329","type":"journal-article","created":{"date-parts":[[2021,10,29]],"date-time":"2021-10-29T03:52:35Z","timestamp":1635479555000},"page":"4329","source":"Crossref","is-referenced-by-count":7,"title":["On Satellite-Borne GPS Data Quality and Reduced-Dynamic Precise Orbit Determination of HY-2C: A Case of Orbit Validation with Onboard DORIS Data"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6359-7383","authenticated-orcid":false,"given":"Hengyang","family":"Guo","sequence":"first","affiliation":[{"name":"College of Geodesy and Geomatics, Shandong University of Science and Technology, Qingdao 266590, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1817-1505","authenticated-orcid":false,"given":"Jinyun","family":"Guo","sequence":"additional","affiliation":[{"name":"College of Geodesy and Geomatics, Shandong University of Science and Technology, Qingdao 266590, China"}]},{"given":"Zhouming","family":"Yang","sequence":"additional","affiliation":[{"name":"College of Geodesy and Geomatics, Shandong University of Science and Technology, Qingdao 266590, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9342-730X","authenticated-orcid":false,"given":"Guangzhe","family":"Wang","sequence":"additional","affiliation":[{"name":"College of Geodesy and Geomatics, Shandong University of Science and Technology, Qingdao 266590, China"}]},{"given":"Linhu","family":"Qi","sequence":"additional","affiliation":[{"name":"College of Geodesy and Geomatics, Shandong University of Science and Technology, Qingdao 266590, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5468-1591","authenticated-orcid":false,"given":"Mingsen","family":"Lin","sequence":"additional","affiliation":[{"name":"National Satellite Ocean Application Service, Beijing 100081, China"},{"name":"Key Laboratory of Space Ocean Remote Sensing and Application, MNR, Beijing 100081, China"}]},{"given":"Hailong","family":"Peng","sequence":"additional","affiliation":[{"name":"National Satellite Ocean Application Service, Beijing 100081, China"},{"name":"Key Laboratory of Space Ocean Remote Sensing and Application, MNR, Beijing 100081, China"}]},{"given":"Bing","family":"Ji","sequence":"additional","affiliation":[{"name":"Department of Navigation Engineering, Naval University of Engineering, Wuhan 430033, China"}]}],"member":"1968","published-online":{"date-parts":[[2021,10,28]]},"reference":[{"key":"ref_1","first-page":"97","article-title":"Precise orbit determination technology based on dual-frequency GPS solution for HY-2 satellite","volume":"16","author":"Lin","year":"2014","journal-title":"Eng. Sci."},{"key":"ref_2","first-page":"1185","article-title":"Progress and prospect of Chinese ocean satellites","volume":"20","author":"Jiang","year":"2016","journal-title":"J. Remote Sens."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2447","DOI":"10.1007\/s00190-018-1143-1","article-title":"Multi-GNSS orbit determination using satellite laser ranging","volume":"93","author":"Bury","year":"2019","journal-title":"J. Geod."},{"key":"ref_4","first-page":"4333","article-title":"Geometric solution method of SLR station coordinate based on multi-LEO satellites","volume":"63","author":"Wang","year":"2020","journal-title":"Chin. J. Geophys."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Strugarek, D., So\u015bnica, K., Arnold, D., J\u00e4ggi, A., Zajdel, R., Bury, G., and Dro\u017cd\u017cewski, M. (2019). Determination of Global Geodetic Parameters Using Satellite Laser Ranging Measurements to Sentinel-3 Satellites. Remote Sens., 11.","DOI":"10.3390\/rs11192282"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"102","DOI":"10.1007\/s10291-020-01015-9","article-title":"High-precision orbit determination for a LEO nanosatellite using BDS-3","volume":"24","author":"Zhao","year":"2020","journal-title":"GPS Solut."},{"key":"ref_7","first-page":"12","article-title":"The study of HY-2A satellite engineering development and in-orbit movement","volume":"15","author":"Zhang","year":"2013","journal-title":"Eng. Sci."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"24449","DOI":"10.1029\/94JC01171","article-title":"GPS precise tracking of TOPEX\/POSEIDON: Results and implications","volume":"99","author":"Bertiger","year":"1994","journal-title":"J. Geophys. Res. Ocenas"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"788","DOI":"10.1016\/j.asr.2020.10.012","article-title":"Dynamic GPS-based LEO orbit determination with 1 cm precision using the Bernese GNSS Software","volume":"67","author":"Mao","year":"2020","journal-title":"Adv. Space Res."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2131","DOI":"10.1016\/j.asr.2006.02.021","article-title":"Precise orbit determination for GRACE using accelerometer data","volume":"38","author":"Kang","year":"2006","journal-title":"Adv. Space Res."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"376","DOI":"10.1016\/j.asr.2005.04.066","article-title":"Kinematic positioning of LEO and GPS satellites and IGS stations on the ground","volume":"36","author":"Rothacher","year":"2005","journal-title":"Adv. Space Res."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"24","DOI":"10.2514\/3.20600","article-title":"Reduced-dynamic technique for precise orbit determination of low earth satellites","volume":"14","author":"Wu","year":"1991","journal-title":"J. Guid. Control. Dyn."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1007\/s40328-020-00324-2","article-title":"On GPS data quality of GRACE-FO and GRACE satellites: Effects of phase center variation and satellite attitude on precise orbit determination","volume":"56","author":"Xia","year":"2021","journal-title":"Acta Geod. Geophys."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"477","DOI":"10.1007\/s00190-008-0256-3","article-title":"Precise orbit determination for the FORMOSAT-3\/COSMIC satellite mission using GPS","volume":"83","author":"Hwang","year":"2009","journal-title":"J. Geod."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1875","DOI":"10.1016\/S0273-1177(03)00159-5","article-title":"Precise orbit determination for GRACE","volume":"31","author":"Kang","year":"2003","journal-title":"Adv. Space Res."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"299","DOI":"10.1080\/01490410490465300","article-title":"One-Centimeter Orbit Determination for Jason-1: New GPS-Based Strategies","volume":"27","author":"Haines","year":"2004","journal-title":"Mar. Geod."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1638","DOI":"10.1016\/j.asr.2007.02.053","article-title":"Precise orbit determination for the GOCE satellite using GPS","volume":"39","author":"Bock","year":"2007","journal-title":"Adv. Space Res."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"95","DOI":"10.1007\/s11770-012-0319-3","article-title":"On simulation of precise orbit determination of HY-2 with centimeter precision based on satellite-borne GPS technique","volume":"9","author":"Guo","year":"2012","journal-title":"Appl. Geophys."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"541","DOI":"10.1029\/94GL00010","article-title":"First assessment of GPS-based reduced dynamic orbit determination on TOPEX\/Poseidon","volume":"21","author":"Yunck","year":"2013","journal-title":"Geophys. Res. Lett."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"62","DOI":"10.1007\/s10291-021-01103-4","article-title":"Assessment of single-difference and track-to-track ambiguity resolution in LEO precise orbit determination","volume":"25","author":"Zhou","year":"2021","journal-title":"GPS Solut."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"47","DOI":"10.1007\/s00190-006-0029-9","article-title":"Pseudo-Stochastic Orbit Modeling Techniques for Low-Earth Orbiters","volume":"80","author":"Hugentobler","year":"2006","journal-title":"J. Geod."},{"key":"ref_22","first-page":"52","article-title":"Centimeter Level Orbit Determination for HY2A Using GPS Data","volume":"38","author":"Guo","year":"2013","journal-title":"Geomat. Form. Sci. Wuhan Univ."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Gong, X.W., Sang, J.Z., Wang, F.H., and Li, X.X. (2020). A More Reliable Orbit Initialization Method for LEO Precise Orbit Determination Using GNSS. Remote Sens., 12.","DOI":"10.3390\/rs12213646"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"74","DOI":"10.1007\/s10291-003-0055-5","article-title":"In-flight performance analysis of the CHAMP BlackJack GPS Receiver","volume":"7","author":"Montenbruck","year":"2003","journal-title":"GPS Solut."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"3412","DOI":"10.1109\/TGRS.2008.2004789","article-title":"Modeling Orbit Dynamics of FORMOSAT-3\/COSMIC Satellites for Recovery of Temporal Gravity Variations","volume":"46","author":"Hwang","year":"2008","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"2812","DOI":"10.1016\/j.asr.2017.05.001","article-title":"In-orbit performance of GNOS on-board FY3-C and the enhancements for FY3-D satellite","volume":"60","author":"Cai","year":"2017","journal-title":"Adv. Space Res."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"121","DOI":"10.1007\/s10291-009-0145-0","article-title":"Quality assessment of FORMOSAT-3\/COSMIC and GRACE GPS observables: Analysis of multipath, ionospheric delay and phase residual in orbit determination","volume":"14","author":"Hwang","year":"2009","journal-title":"GPS Solut."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"209","DOI":"10.1093\/gji\/ggw265","article-title":"Horizontal and vertical velocities derived from the IDS contribution to ITRF2014, and comparisons with geophysical models","volume":"207","author":"Moreaux","year":"2016","journal-title":"Geophys. J. Int."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"2677","DOI":"10.1016\/j.asr.2016.06.024","article-title":"Precise orbit determination and station position estimation using DORIS RINEX data","volume":"58","author":"Lemoine","year":"2016","journal-title":"Adv. Space Res."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"497","DOI":"10.1016\/0094-5765(91)90032-Z","article-title":"DORIS (Doppler orbitography and radiopositioning integrated from space): System assessment results with DORIS on SPOT 2","volume":"25","author":"Dorrer","year":"1991","journal-title":"Acta Astronaut."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"753","DOI":"10.1080\/01490410490889085","article-title":"DORIS-DIODE: Jason-1 has a Navigator on Board","volume":"27","author":"Jayles","year":"2004","journal-title":"Mar. Geod."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1441","DOI":"10.1016\/j.asr.2009.12.002","article-title":"Jason-2 DORIS phase measurement processing","volume":"45","author":"Mercier","year":"2010","journal-title":"Adv. Space Res."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"497","DOI":"10.1007\/s00190-006-0075-3","article-title":"DORIS time bias estimated using Jason-1, TOPEX\/Poseidon and ENVISAT orbits","volume":"80","author":"Zelensky","year":"2006","journal-title":"J. Geod."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"611","DOI":"10.1016\/j.actaastro.2006.07.012","article-title":"Analysis of DORIS range-rate residuals for TOPEX\/Poseidon, Jason, Envisat and SPOT","volume":"60","author":"Doornbos","year":"2007","journal-title":"Acta Astronaut."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"904","DOI":"10.1016\/j.eng.2019.09.001","article-title":"Precise Orbit Determination for the FY-3C Satellite Using Onboard BDS and GPS Observations from 2013, 2015, and 2017","volume":"6","author":"Li","year":"2019","journal-title":"Engineering"},{"key":"ref_36","unstructured":"CNES (2021, June 24). HY-2C input data for Precise Orbit Determination. Available online: https:\/\/ids-doris.org\/analysis-documents.html."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"353","DOI":"10.1007\/s00190-008-0281-2","article-title":"GNSS processing at CODE: Status report","volume":"83","author":"Dach","year":"2009","journal-title":"J. Geod."},{"key":"ref_38","first-page":"1","article-title":"POD of small LEO satellites based on precise real-time MADOCA and SBAS-aided PPP corrections","volume":"25","author":"Wang","year":"2021","journal-title":"GPS Solut."},{"key":"ref_39","unstructured":"Dach, R., Andritsch, F., Arnold, D., Vertone, S., and Thaller, D. (2015). Bernese GNSS Software Version 5.2. User Manual, Astronomical Institute, University of Bern, Bern Open Publishing."},{"key":"ref_40","unstructured":"Flavien, M., John, M., and Sabine, H. (2021, June 24). First POD Results on HY-2C. Available online: https:\/\/ids-doris.org\/images\/documents\/report\/AWG202104\/IDSAWG202104-Mercier-PODHY2C.pdf."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1016\/S0273-1177(02)00277-6","article-title":"The International Laser Ranging Service","volume":"30","author":"Pearlman","year":"2002","journal-title":"Adv. Space Res."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1484","DOI":"10.1016\/j.asr.2010.05.015","article-title":"DORIS system: The new age","volume":"46","author":"Auriol","year":"2010","journal-title":"Adv. Space Res."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1023\/A:1026253328154","article-title":"Aiming at a 1-cm Orbit for Low Earth Orbiters: Reduced-Dynamic and Kinematic Precise Orbit Determination","volume":"108","author":"Visser","year":"2003","journal-title":"Space Sci. Rev."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1113","DOI":"10.1016\/j.asr.2012.01.016","article-title":"Adjustable box-wing model for solar radiation pressure impacting GPS satellites","volume":"49","author":"Hugentobler","year":"2012","journal-title":"Adv. Space Res."},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Zhang, B.B., Wang, Z., Zhou, L., Feng, J., Qiu, Y., and Li, F. (2017). Precise Orbit Solution for Swarm Using Space-Borne GPS Data and Optimized Pseudo-Stochastic Pulses. Sensors, 17.","DOI":"10.3390\/s17030635"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"279","DOI":"10.1007\/BF02521844","article-title":"Contributions to the theory of atmospheric refraction","volume":"105","author":"Saastamoinen","year":"1972","journal-title":"Bull. G\u00e9od."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"3227","DOI":"10.1029\/95JB03048","article-title":"Global mapping functions for the atmosphere delay at radio wavelengths","volume":"101","author":"Niell","year":"1996","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_48","first-page":"775","article-title":"G-Nut\/Anubis: Open-Source Tool for Multi-GNSS Data Monitoring with a Multipath Detection for New Signals, Frequencies and Constellations","volume":"Volume 143","author":"Vaclavovic","year":"2015","journal-title":"Gravity, Geoid and Earth Observation"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"29841","DOI":"10.1109\/ACCESS.2021.3059296","article-title":"Effect of Higher-Order Ionospheric Delay on Precise Orbit Determination of GRACE-FO Based on Satellite-Borne GPS Technique","volume":"9","author":"Qi","year":"2019","journal-title":"IEEE Access"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"1883","DOI":"10.1016\/S0273-1177(03)00162-5","article-title":"The CHAMP-only earth gravity field model EIGEN-2","volume":"31","author":"Reigber","year":"2003","journal-title":"Adv. Space Res."},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Liu, M., Yuan, Y., Ou, J., and Chai, Y. (2019). Research on Attitude Models and Antenna Phase Center Correction for Jason-3 Satellite Orbit Determination. Sensors, 19.","DOI":"10.3390\/s19102408"},{"key":"ref_52","doi-asserted-by":"crossref","unstructured":"Yuan, J.J., Zhou, S.S., Hu, X.G., Yang, L., Cao, J.F., Li, K., and Liao, M. (2021). Impact of Attitude Model, Phase Wind-Up and Phase Center Variation on Precise Orbit and Clock Offset Determination of GRACE-FO and CentiSpace-1. Remote. Sens., 13.","DOI":"10.3390\/rs13132636"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/s10291-019-0899-y","article-title":"Improving LEO precise orbit determination with BDS PCV calibration","volume":"23","author":"Lu","year":"2019","journal-title":"GPS Solut."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"1145","DOI":"10.1007\/s00190-009-0333-2","article-title":"Phase center modeling for LEO GPS receiver antennas and its impact on precise orbit determination","volume":"83","author":"Dach","year":"2009","journal-title":"J. Geod."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"1166","DOI":"10.1016\/j.asr.2019.06.014","article-title":"Impact of GPS receiver antenna GRAPHIC residual variations on single-frequency orbit determination of LEO satellites","volume":"64","author":"Shao","year":"2019","journal-title":"Adv. Space Res."},{"key":"ref_56","first-page":"879","article-title":"Precision Orbit Determination of CHAMP Satellite with cm-level Accuracy","volume":"31","author":"Zhao","year":"2006","journal-title":"Geomat. Inf. Sci. Wuhan Univ."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/s00190-020-01414-3","article-title":"GRACE-FO precise orbit determination and gravity recovery","volume":"94","author":"Kang","year":"2020","journal-title":"J. Geod."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"47","DOI":"10.5194\/adgeo-1-47-2003","article-title":"Kinematic and reduced-dynamic precise orbit determination of low earth orbiters","volume":"1","author":"Rothacher","year":"2003","journal-title":"Adv. Geosci."},{"key":"ref_59","unstructured":"Petit, G., and Luzum, B. (2010). IERS Conventions IERS Technical Note, Verlag des Bundesamtsf\u00fcr Kartographie and Geod\u00e4sie."},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"201","DOI":"10.1186\/s40623-018-0973-7","article-title":"Estimation of SLR station coordinates by means of SLR measurements to kinematic orbit of LEO satellites","volume":"70","author":"Guo","year":"2018","journal-title":"Earth Planets Space"},{"key":"ref_61","doi-asserted-by":"crossref","first-page":"189","DOI":"10.1029\/2004GL020308","article-title":"High-accuracy zenith delay prediction at optical wavelengths","volume":"31","author":"Mendes","year":"2004","journal-title":"Geophys. Res. Lett."},{"key":"ref_62","doi-asserted-by":"crossref","first-page":"2150","DOI":"10.1520\/JTE20170779","article-title":"Performance Evaluation of Three Atmospheric Density Models on HY-2A Precise Orbit Determination Using DORIS Range-Rate Data","volume":"47","author":"Kong","year":"2018","journal-title":"J. Test. Eval."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/21\/4329\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,1,7]],"date-time":"2025-01-07T10:40:41Z","timestamp":1736246441000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/21\/4329"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,10,28]]},"references-count":62,"journal-issue":{"issue":"21","published-online":{"date-parts":[[2021,11]]}},"alternative-id":["rs13214329"],"URL":"https:\/\/doi.org\/10.3390\/rs13214329","relation":{},"ISSN":["2072-4292"],"issn-type":[{"type":"electronic","value":"2072-4292"}],"subject":[],"published":{"date-parts":[[2021,10,28]]}}}