{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,8]],"date-time":"2026-02-08T08:11:15Z","timestamp":1770538275815,"version":"3.49.0"},"reference-count":34,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2018,11,22]],"date-time":"2018-11-22T00:00:00Z","timestamp":1542844800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Nature Science Foundation of China","award":["41674004"],"award-info":[{"award-number":["41674004"]}]},{"name":"National Nature Science Foundation of China","award":["41574030"],"award-info":[{"award-number":["41574030"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The characteristics of the improved Atomic Frequency Standard (AFS) operated on the latest BeiDou-3 experimental satellites are analyzed from day-of-year (DOY) 254 to 281, of the year 2017, considering the following three aspects: stability, periodicity, and prediction precision. The two-step method of Precise Orbit Determination (POD) is used to obtain the precise clock offsets. We presented the stability of such new clocks and studied the influence of the uneven distribution of the ground stations on the stability performance of the clock. The results show that the orbit influence on the Medium Earth Orbit (MEO) clock offsets is the largest of three satellite types, especially from     3 \u00d7   10  3      s to     8.64 \u00d7   10  4      s. Considering this orbit influence, the analysis shows that the Passive Hydrogen Maser (PHM) clock carried on C32 is approximately     2.6 \u00d7   10   \u2212 14       at an interval of       10  4     , and has the best stability for any averaging intervals among the BeiDou satellite clocks, which currently achieves a level comparable to that of the PHM clock of Galileo, and the rubidium (Rb) clocks of Global Positioning System (GPS) Block IIF. The stability of the improved Rb AFS on BeiDou-3 is also superior to that of BeiDou-2 from     3 \u00d7   10  2      s to     3 \u00d7   10  3      s, and comparable to that of Rb AFS on the Galileo. Moreover, the periodicity of the PHM clock and the improved Rb clock are presented. For the PHM clock, the amplitudes are obviously reduced, while the new Rb clocks did not show a visible improvement, which will need further analysis in the future. As expected, the precision of the short-term clock prediction is improved because of the better characteristics of AFS. The Root Mean Square (RMS) of 1-h clock prediction is less than 0.16 ns.<\/jats:p>","DOI":"10.3390\/rs10111847","type":"journal-article","created":{"date-parts":[[2018,11,22]],"date-time":"2018-11-22T09:18:25Z","timestamp":1542878305000},"page":"1847","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":26,"title":["Characteristics of BeiDou-3 Experimental Satellite Clocks"],"prefix":"10.3390","volume":"10","author":[{"given":"Yifei","family":"Lv","sequence":"first","affiliation":[{"name":"GNSS Research Center, Wuhan University, Wuhan 430079, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5760-5666","authenticated-orcid":false,"given":"Tao","family":"Geng","sequence":"additional","affiliation":[{"name":"GNSS Research Center, Wuhan University, Wuhan 430079, China"},{"name":"Collaborative Innovation Center of Geospatial Technology, Wuhan 430079, China"}]},{"given":"Qile","family":"Zhao","sequence":"additional","affiliation":[{"name":"GNSS Research Center, Wuhan University, Wuhan 430079, China"},{"name":"Collaborative Innovation Center of Geospatial Technology, Wuhan 430079, China"}]},{"given":"Jingnan","family":"Liu","sequence":"additional","affiliation":[{"name":"GNSS Research Center, Wuhan University, Wuhan 430079, China"}]}],"member":"1968","published-online":{"date-parts":[[2018,11,22]]},"reference":[{"key":"ref_1","unstructured":"The State Council Information Office of the People\u2019s Republic of China (2018, April 17). China\u2019s BeiDou Navigation Satellite System, Available online: http:\/\/www.BeiDou.gov.cn\/xt\/gfxz\/201712\/P020171221333863515306.pdf."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"S213","DOI":"10.1088\/0026-1394\/48\/4\/S13","article-title":"BeiDou Navigation Satellite System and its time scales","volume":"48","author":"Han","year":"2011","journal-title":"Metrologia"},{"key":"ref_3","unstructured":"China Satellite Navigation Office (2018, April 17). BeiDou Navigation Satellite System Signal in Space Interface Control Document Open Service Signal (Version 2.1), Available online: http:\/\/www.beidou.gov.cn\/xt\/gfxz\/201805\/P020180507527106075323.pdf."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"2813","DOI":"10.1007\/s11434-011-4627-4","article-title":"Contribution of the Compass satellite navigation system to global PNT users","volume":"56","author":"Yang","year":"2011","journal-title":"Chin. Sci. Bull."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"60","DOI":"10.1007\/s10291-018-0726-x","article-title":"Elevation-dependent pseudorange variation characteristics analysis for the new-generation BeiDou satellite navigation system","volume":"22","author":"Zhou","year":"2018","journal-title":"GPS Solut."},{"key":"ref_6","first-page":"1","article-title":"Orbit determination and time synchronization for new-generation BeiDou satellites: Preliminary results","volume":"46","author":"Chen","year":"2016","journal-title":"Sci. Sin. Phys. Mech. Astron."},{"key":"ref_7","unstructured":"China Satellite Navigation Office (2018, April 17). BeiDou Navigation Satellite System Signal in Space Interface Control Document Open Service Signal B1C (Version 1.0), Available online: http:\/\/www.BeiDou.gov.cn\/xt\/gfxz\/201712\/P020171226741342013031.pdf."},{"key":"ref_8","unstructured":"China Satellite Navigation Office (2018, April 17). BeiDou Navigation Satellite System Signal in Space Interface Control Document Open Service Signal B2a (Version 1.0), Available online: http:\/\/www.BeiDou.gov.cn\/xt\/gfxz\/201712\/P020171226742357364174.pdf."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1225","DOI":"10.1007\/s00190-017-1020-3","article-title":"Initial assessment of the COMPASS\/BeiDou-3: New-generation navigation signals","volume":"91","author":"Zhang","year":"2017","journal-title":"J. Geodesy"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Tan, B., Tan, B., Yuan, Y., Yuan, Y., Wen, M., Wen, M., Ning, Y., Ning, Y., Liu, X., and Liu, X. (2016). Initial Results of the Precise Orbit Determination for the New-Generation BeiDou Satellites (BeiDou-3) Based on the iGMAS Network. ISPRS Int. J. Geo-Inf., 5.","DOI":"10.3390\/ijgi5110196"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Xie, X., Geng, T., Zhao, Q., Liu, J., and Wang, B. (2017). Performance of BDS-3: Measurement Quality Analysis, Precise Orbit and Clock Determination. Sensors, 17.","DOI":"10.3390\/s17061233"},{"key":"ref_12","first-page":"367","article-title":"Precise orbit and clock determination for BeiDou-3 experimental satellites with yaw attitude analysis","volume":"22","author":"Zhao","year":"2017","journal-title":"GPS Solut."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"647","DOI":"10.1007\/s10291-018-0706-1","article-title":"Performance of the BDS3 experimental satellite passive hydrogen maser","volume":"22","author":"Wu","year":"2018","journal-title":"GPS Solut."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2290","DOI":"10.1007\/s11433-012-4942-z","article-title":"Positioning accuracy assessment for the 4GEO\/5IGSO\/2MEO constellation of COMPASS","volume":"55","author":"Zhou","year":"2012","journal-title":"Sci. China Phys. Mech. Astron."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1089","DOI":"10.1007\/s11433-011-4342-9","article-title":"Orbit determination and time synchronization for a GEO\/IGSO satellite navigation constellation with regional tracking network","volume":"54","author":"Zhou","year":"2011","journal-title":"Sci. China Phys. Mech. Astron."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1191","DOI":"10.1007\/s10291-017-0602-0","article-title":"Improving BDS integer ambiguity resolution using satellite-induced code bias correction for precise orbit determination","volume":"21","author":"Geng","year":"2017","journal-title":"GPS Solut."},{"key":"ref_17","unstructured":"Jiao, W. (2014, January 21\u201323). International GNSS Monitoring and Assessment System (iGMAS) and latest progress. Proceedings of the 2014 China Satellite Navigation Conference (CSNC), Nanjing, China."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1007\/s10291-013-0361-5","article-title":"Galileo orbit determination using combined GNSS and SLR observations","volume":"19","author":"Hackel","year":"2014","journal-title":"GPS Solut."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"259","DOI":"10.1007\/s10291-014-0436-y","article-title":"Precise orbit determination of BeiDou constellation: Method comparison","volume":"20","author":"Lou","year":"2015","journal-title":"GPS Solut."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1007\/s00190-015-0862-9","article-title":"Precise orbit determination for quad-constellation satellites at Wuhan University: Strategy, result validation, and comparison","volume":"90","author":"Guo","year":"2016","journal-title":"J. Geodesy"},{"key":"ref_21","first-page":"247","article-title":"Atmospheric Correction for the Troposphere and Stratosphere in Radio Ranging Satellites","volume":"15","author":"Saastamoinen","year":"1972","journal-title":"Use Artif. Satell. Geodesy"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"L07304","DOI":"10.1029\/2005GL025546","article-title":"Global Mapping Function (GMF): A new empirical mapping function based on numerical weather model data","volume":"33","author":"Boehm","year":"2006","journal-title":"Geophys. Res. Lett."},{"key":"ref_23","first-page":"1647","article-title":"Effects of antenna orientation on GPS carrier phase","volume":"18","author":"Wu","year":"1992","journal-title":"Astrodynamics"},{"key":"ref_24","unstructured":"Petit, G., and Luzum, B. (2010, January 17\u201319). IERS conventions (2010) (No. IERS-TN-36). Proceedings of the International earth rotation and reference systems service (IERS), Meudon, France."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"50","DOI":"10.1007\/PL00012757","article-title":"A New Solar Radiation Pressure Model for GPS Satellites","volume":"2","author":"Springer","year":"1999","journal-title":"GPS Solut."},{"key":"ref_26","first-page":"686","article-title":"Real-Time Precise BDS Clock Estimation with the Undifferenced Observation","volume":"5","author":"Zhao","year":"2016","journal-title":"Geomat. Inf. Sci. Wuhan Univ."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Riley, W.J., and Riley, W.J. (2008). Handbook of Frequency Stability Analysis, National Institute of Standards and Technology.","DOI":"10.6028\/NIST.SP.1065"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"S134","DOI":"10.1088\/0026-1394\/45\/6\/S19","article-title":"Estimating the Allan variance in the presence of long periods of missing data and outliers","volume":"45","author":"Sesia","year":"2008","journal-title":"Metrologia"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"783","DOI":"10.1007\/s10291-015-0488-7","article-title":"Analysis of BDS satellite clocks in orbit","volume":"20","author":"Wang","year":"2015","journal-title":"GPS Solut."},{"key":"ref_30","unstructured":"(2018, April 17). GLONASS Constellation Status (17-11-21). Available online: http:\/\/www2.unb.ca\/gge\/Resources\/GLONASSConstellationStatus.txt."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"295","DOI":"10.1007\/s10291-012-0278-4","article-title":"Short-term analysis of GNSS clocks","volume":"17","author":"Hauschild","year":"2012","journal-title":"GPS Solut."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"443","DOI":"10.1137\/S003614450343200X","article-title":"Accelerating the Nonuniform Fast Fourier Transform","volume":"46","author":"Greengard","year":"2004","journal-title":"SIAM Rev."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.jcp.2004.12.004","article-title":"The type 3 nonuniform FFT and its applications","volume":"206","author":"Lee","year":"2005","journal-title":"J. Comput. Phys."},{"key":"ref_34","unstructured":"(2017, October 17). NUFFT (NFFT, USFFT) Software. Available online: https:\/\/cims.nyu.edu\/cmcl\/nufft\/nufft.html."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/11\/1847\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:31:15Z","timestamp":1760196675000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/11\/1847"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,11,22]]},"references-count":34,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2018,11]]}},"alternative-id":["rs10111847"],"URL":"https:\/\/doi.org\/10.3390\/rs10111847","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,11,22]]}}}