{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,29]],"date-time":"2025-10-29T06:24:53Z","timestamp":1761719093957,"version":"build-2065373602"},"reference-count":41,"publisher":"MDPI AG","issue":"20","license":[{"start":{"date-parts":[[2021,10,19]],"date-time":"2021-10-19T00:00:00Z","timestamp":1634601600000},"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":["11903040, 41674034, 41974032"],"award-info":[{"award-number":["11903040, 41674034, 41974032"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The technique of carrier phase (CP), based on the global navigation satellite system (GNSS), has proven to be a highly effective spatial tool in the field of time and frequency transfer with sub-nanosecond accuracy. The rapid development of real-time GNSS satellite orbit and clock determinations has enabled GNSS time and frequency transfer using the CP technique to be performed in real-time mode, without any issues associated with latency. In this contribution, we preliminarily built the prototype system of real-time multi-GNSS time and frequency transfer service in National Time Service Center (NTSC) of the Chinese Academy of Sciences (CAS), which undertakes the task to generate, maintains and transmits the national standard of time and frequency UTC(NTSC). The comprehensive assessment of the availability and quality of the service system were provided. First, we assessed the multi-GNSS state space representation (SSR) correction generated in real-time multi-GNSS prototype system by combining broadcast ephemeris through a comparison with the GeoForschungsZentrum (GFZ) final products. The statistical results showed that the orbit precision in three directions was smaller than 6 cm for global positioning system (GPS) and smaller than approximately 10 cm for BeiDou satellite system (BDS). The root mean square (RMS) values of clock differences for GPS were approximately 2.74 and 6.74 ns for the GEO constellation of BDS, 3.24 ns for IGSO, and 1.39 ns for MEO. The addition, the GLObal NAvigation Satellite System (GLONASS) and Galileo satellite navigation system (Galileo) were 4.34 and 1.32 ns, respectively. In order to assess the performance of real-time multi-GNSS time and frequency transfer in a prototype system, the four real-time time transfer links, which used UTC(NTSC) as the reference, were employed to evaluate the performance by comparing with the solution determined using the GFZ final products. The RMS could reach sub-nanosecond accuracy in the two solutions, either in the SSR or GFZ solution, or in GPS, BDS, GLONASS, and Galileo. The frequency stability within 10,000 s was 3.52 \u00d7 10\u221212 for SSR and 3.47 \u00d7 10\u221212 for GFZ and GPS, 3.63 \u00d7 10\u221212 for SSR and 3.53 \u00d7 10\u221212 for GFZ for BDS, 3.57 \u00d7 10\u221212 for SSR and 3.52 \u00d7 10\u221212 for GFZ for GLONASS, and 3.56 \u00d7 10\u221212 for SSR and 3.48 \u00d7 10\u221212 for GFZ for Galileo.<\/jats:p>","DOI":"10.3390\/rs13204184","type":"journal-article","created":{"date-parts":[[2021,10,20]],"date-time":"2021-10-20T21:31:26Z","timestamp":1634765486000},"page":"4184","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Performance of Multi-GNSS Real-Time UTC(NTSC) Time and Frequency Transfer Service Using Carrier Phase Observations"],"prefix":"10.3390","volume":"13","author":[{"given":"Pengfei","family":"Zhang","sequence":"first","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Xi\u2019an 710600, China"},{"name":"Key Laboratory of Time and Frequency Primary Standards, Chinese Academy of Sciences, Xi\u2019an 710600, China"},{"name":"State Key Laboratory of Geo-Information Engineering, Xi\u2019an Research Institute of Surveying and Mapping, Xi\u2019an 710054, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Rui","family":"Tu","sequence":"additional","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Xi\u2019an 710600, China"},{"name":"University of Chinese Academy of Sciences, Yu Quan Road, Beijing 100049, China"},{"name":"Key Laboratory of Precision Navigation Positioning and Timing Technology, Chinese Academy of Sciences, Xi\u2019an 710600, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xiaochun","family":"Lu","sequence":"additional","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Xi\u2019an 710600, China"},{"name":"University of Chinese Academy of Sciences, Yu Quan Road, Beijing 100049, China"},{"name":"Key Laboratory of Precision Navigation Positioning and Timing Technology, Chinese Academy of Sciences, Xi\u2019an 710600, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lihong","family":"Fan","sequence":"additional","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Xi\u2019an 710600, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7322-2953","authenticated-orcid":false,"given":"Rui","family":"Zhang","sequence":"additional","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Xi\u2019an 710600, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,10,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1088\/0026-1394\/31\/1\/014","article-title":"Technical directives for standardization of GPS time receiver software","volume":"31","author":"Allan","year":"1994","journal-title":"Metrologia"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Allan, D.W., and Weiss, M. (1980, January 28\u201330). Accurate time and frequency transfer during common-view of a GPS satellite. Proceedings of the 1980 IEEE Frequency Control Symposium, Philadelphia, PA, USA.","DOI":"10.1109\/FREQ.1980.200424"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1088\/0026-1394\/45\/1\/006","article-title":"GPS All in View time transfer for TAI computation","volume":"45","author":"Petit","year":"2008","journal-title":"Metrologia"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1088\/0026-1394\/49\/1\/009","article-title":"Use of GLONASS for UTC time transfer","volume":"49","author":"Jiang","year":"2012","journal-title":"Metrologia"},{"key":"ref_5","unstructured":"Defraigne, P., Bruyninx, C., and Guyennon, N. (June, January 29). PPP and phase only GPS frequency transfer. Proceedings of the IEEE International Frequency Control Symposium Jointly with the 21st European Frequency and Time Forum (EFTF\u2019 07), Geneva, Switzerland."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"265","DOI":"10.1016\/j.asr.2010.07.003","article-title":"Combining GPS and GLONASS for time and frequency transfer","volume":"47","author":"Defraigne","year":"2011","journal-title":"Adv. Space Res."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"239","DOI":"10.1007\/s10291-007-0054-z","article-title":"On the link between GPS pseudorange noise and day-boundary discontinuities in geodetic time transfer solutions","volume":"11","author":"Defraigne","year":"2007","journal-title":"GPS Solut."},{"key":"ref_8","first-page":"273785","article-title":"GPS carrier phase time transfer using single difference integer ambiguity resolution","volume":"2008","author":"Delporte","year":"2008","journal-title":"Int. J. Navig. Obs."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"175","DOI":"10.1088\/1681-7575\/aaa673","article-title":"Progress of BeiDou time transfer at NTSC","volume":"55","author":"Guang","year":"2018","journal-title":"Metrologia"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"04018013","DOI":"10.1061\/(ASCE)SU.1943-5428.0000268","article-title":"Day-Boundary Discontinuity in GPS Carrier-Phase Time Transfer Using a Geodetic Data Solution Strategy","volume":"145","author":"Zhang","year":"2019","journal-title":"J. Surv. Eng."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Tu, R., Zhang, P., Zhang, R., Liu, J., and Lu, X. (2018). Modeling and Assessment of Precise Time Transfer by Using BeiDou Navigation Satellite System Triple-Frequency Signals. Sensors, 18.","DOI":"10.3390\/s18041017"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"607","DOI":"10.1007\/s00190-015-0802-8","article-title":"Accuracy and reliability of multi-GNSS real-time precise positioning: GPS, GLONASS, BeiDou, and Galileo","volume":"89","author":"Li","year":"2015","journal-title":"J. Geod."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1671","DOI":"10.1016\/j.asr.2017.01.011","article-title":"The Multi-GNSS Experiment (MGEX) of the International GNSS Service (IGS)\u2013Achievements, prospects and challenges","volume":"59","author":"Montenbruck","year":"2017","journal-title":"Adv. Space Res."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"187","DOI":"10.1007\/s10291-014-0379-3","article-title":"A Galileo IOV assessment: Measurement and position domain","volume":"19","author":"Gioia","year":"2015","journal-title":"GPS Solut."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"673","DOI":"10.1007\/1345_2015_120","article-title":"GFZ Global Multi-GNSS Network and Data Processing Results","volume":"Volume 143","author":"Rizos","year":"2015","journal-title":"IAG 150 Years. International Association of Geodesy Symposia"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1007\/s10291-014-0369-5","article-title":"IGS RTS precise orbits and clocks verification and quality degradation over time","volume":"19","author":"Hadas","year":"2015","journal-title":"GPS Solut."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1088\/0026-1394\/51\/1\/33","article-title":"UTCr: A rapid realization of UTC","volume":"51","author":"Petit","year":"2013","journal-title":"Metrologia"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"165","DOI":"10.1007\/s10291-014-0377-5","article-title":"Monitoring of UTC(k)\u2019s using PPP and IGS real-time products","volume":"19","author":"Defraigne","year":"2015","journal-title":"GPS Solut."},{"key":"ref_19","unstructured":"Jade Morton, Y. (2021). GNSS Precise Point Positioning. Chapter 20 in Position, Navigation, and Timing Technologies in the 21st Century: Integrated Satellite Navigation, Sensor Systems, and Civil Applications, John Wiley & Son."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1186\/s43020-020-0009-x","article-title":"Multi-constellation GNSS precise point positioning with multi-frequency raw observations and dual-frequency observations of ionospheric-free linear combination","volume":"1","author":"An","year":"2020","journal-title":"Satell. Navig."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"10","DOI":"10.1186\/s43020-020-00012-0","article-title":"Precise time scales and navigation systems: Mutual benefits of timekeeping and positioning","volume":"1","author":"Tavella","year":"2020","journal-title":"Satell. Navig."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1003","DOI":"10.1088\/0026-1394\/53\/3\/1003","article-title":"The performance of GPS time and frequency transfer: Comment on \u2018A detailed comparison of two continuous GPS carrier phase time transfer techniques\u2019","volume":"53","author":"Petit","year":"2016","journal-title":"Metrologia"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"14701","DOI":"10.3390\/s150614701","article-title":"Performance Analysis of Several GPS\/Galileo Precise Point Positioning Models","volume":"15","author":"Afifi","year":"2015","journal-title":"Sensors"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Zhang, P., Tu, R., Zhang, R., Gao, Y., and Cai, H. (2018). Combining GPS, BeiDou, and Galileo Satellite Systems for Time and Frequency Transfer Based on Carrier Phase Observations. Remote Sens., 10.","DOI":"10.3390\/rs10020324"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"476","DOI":"10.1088\/0026-1394\/51\/5\/476","article-title":"Link calibration against receiver calibration: An assessment of GPS time transfer uncertainties","volume":"51","author":"Rovera","year":"2014","journal-title":"Metrologia"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1330","DOI":"10.1049\/iet-rsn.2018.5096","article-title":"Study of time link calibration based on GPS carrier phase observation","volume":"12","author":"Zhang","year":"2018","journal-title":"IET Radar Sonar Navig."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Nicolini, L., and Caporali, A. (2018). Investigation on Reference Frames and Time Systems in Multi-GNSS. Remote Sens., 10.","DOI":"10.3390\/rs10010080"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Wang, L., Li, Z., Ge, M., Neitzel, F., Wang, Z., and Yuan, H. (2018). Validation and Assessment of Multi-GNSS Real-Time Precise Point Positioning in Simulated Kinematic Mode Using IGS Real-Time Service. Remote Sens., 10.","DOI":"10.3390\/rs10020337"},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Wang, Z., Li, Z., Wang, L., Wang, X., and Yuan, H. (2018). Assessment of Multiple GNSS Real-Time SSR Products from Different Analysis Centers. ISPRS Int. J. Geo-Inf., 7.","DOI":"10.3390\/ijgi7030085"},{"key":"ref_30","first-page":"15","article-title":"Realization and analysis of real-time precise point positioning based on SSR broadcast ephemeris corrections","volume":"39","author":"Liu","year":"2014","journal-title":"Sci. Surv. Mapp."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Janicka, J., Tomaszewski, D., Rapinski, J., Jagoda, M., and Rutkowska, M. (2020). The Prediction of Geocentric Corrections during Communication Link Outages in PPP. Sensors, 20.","DOI":"10.3390\/s20030602"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Pelc-Mieczkowska, R., and Tomaszewski, D. (2020). Space State Representation Product Evaluation in Satellite Position and Receiver Position Domain. Sensors, 20.","DOI":"10.3390\/s20133791"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"065003","DOI":"10.1088\/1361-6501\/ab0f7f","article-title":"Evaluation of carrier-phase precise time and frequency transfer using different analysis centre products for GNSSs","volume":"30","author":"Zhang","year":"2019","journal-title":"Meas. Sci. Technol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1007\/s10291-020-0955-7","article-title":"Performance of Galileo precise time and frequency transfer models using quad-frequency carrier phase observations","volume":"24","author":"Zhang","year":"2020","journal-title":"GPS Solut."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1225","DOI":"10.1016\/j.asr.2019.11.006","article-title":"Initial accuracy and reliability of current BDS-3 precise positioning, velocity estimation, and time transfer (PVT)","volume":"65","author":"Zhang","year":"2020","journal-title":"Adv. Space Res."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Lin, P., Li, X., Zhang, X., Li, X., Lu, C., Zhao, Q., and Liu, J. (2017). Considering Inter-Frequency Clock Bias for BDS Triple-Frequency Precise Point Positioning. Remote Sens., 9.","DOI":"10.3390\/rs9070734"},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Wang, J., Huang, G., Zhang, Q., Gao, Y., Gao, Y., and Luo, Y. (2020). GPS\/BDS-2\/Galileo Precise Point Positioning Ambiguity Resolution Based on the Uncombined Model. Remote Sens., 12.","DOI":"10.3390\/rs12020304"},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Wang, A., Chen, J., Zhang, Y., Meng, L., and Wang, J. (2019). Performance of Selected Ionospheric Models in Multi-Global Navigation Satellite System Single-Frequency Positioning over China. Remote Sens., 11.","DOI":"10.3390\/rs11172070"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"465","DOI":"10.1017\/S0373463316000771","article-title":"Performance evaluation of single-frequency precise point positioning with GPS, GLONASS, BeiDou and Galileo","volume":"70","author":"Pan","year":"2017","journal-title":"J. Navig."},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Zhang, P., Tu, R., Gao, Y., Hong, J., Han, J., and Lu, X. (2021). Comparison of Multi-GNSS Time and Frequency Transfer Performance Using Overlap-Frequency Observations. Remote Sens., 13.","DOI":"10.3390\/rs13163130"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"16","DOI":"10.1186\/s43020-021-00048-w","article-title":"Recover the abnormal positioning, velocity and timing services caused by BDS satellite orbital maneuvers","volume":"2","author":"Tu","year":"2021","journal-title":"Satell. Navig."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/20\/4184\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T07:18:03Z","timestamp":1760167083000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/20\/4184"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,10,19]]},"references-count":41,"journal-issue":{"issue":"20","published-online":{"date-parts":[[2021,10]]}},"alternative-id":["rs13204184"],"URL":"https:\/\/doi.org\/10.3390\/rs13204184","relation":{},"ISSN":["2072-4292"],"issn-type":[{"type":"electronic","value":"2072-4292"}],"subject":[],"published":{"date-parts":[[2021,10,19]]}}}