{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,31]],"date-time":"2025-12-31T18:27:44Z","timestamp":1767205664378,"version":"build-2238731810"},"reference-count":32,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2019,5,16]],"date-time":"2019-05-16T00:00:00Z","timestamp":1557964800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"the National Science Foundation of China","award":["U1831116"],"award-info":[{"award-number":["U1831116"]}]},{"name":"the Natural Science Foundation of Ningbo","award":["2018A610284"],"award-info":[{"award-number":["2018A610284"]}]},{"name":"the Shanghai science and Technology Commission Project","award":["17DZ1100702"],"award-info":[{"award-number":["17DZ1100702"]}]},{"name":"the National Key R&amp;D plan","award":["2018YFC1406104"],"award-info":[{"award-number":["2018YFC1406104"]}]}],"content-domain":{"domain":["www.mdpi.com"],"crossmark-restriction":true},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>This study introduced a Kalman filtering assimilation model that considers the DCB errors of GPS\/LEO satellites and GNSS stations. The assimilation results and reliability were verified by various types of data, such as ionMap, ionosonde, ISR, and the EDP of ionPrf from COSMIC. The following analyses were carried out. Assimilating the measured ground-based\/spaceborne ionospheric observation data from DOY 010, 2008 and DOY 089, 2012 revealed that the introduction of GPS\/LEO satellite and GPS station DCB errors can effectively suppress the STEC observation errors caused by the single-layer hypothesis. Furthermore, the top of the ionosphere contributes 2.8 TECU (approximately 10\u201320% of the STEC) of electrons during the ionospheric quiet period, greatly influencing the ionospheric assimilation at altitudes of 100\u2013800 km. The assimilation results also show that, after subtracting the influence of the top of the ionosphere, the ionospheric deviation during the quiet period improved from 1.645 TECU to 1.464 TECU; when the ionosphere was active, the standard deviation was improved from 4.408 TECU to 3.536 TECU. The IRI-Imp model introduced by Wu et al. and the IRI (2007) model were used as background fields to compare the effects of COSMIC occultation observation data on the ionospheric assimilation process. Upon comparison, the occultation data introduced by the improved model showed the greatest improvement in the vertical structure of the ionosphere; additionally, the assimilation process reused the horizontal structure information of the occultation data, and the assimilation result (IRI-Imp-Assi) was the most ideal. Due to the lack of an occultation data correction, the IRI2007 model was relatively more prone to errors. With the strategy of the IRI-Imp-Assi model, the introduction of occultation data caused a more significant reduction in the error between the assimilation model with the IRI model as the background field and the ionMap.<\/jats:p>","DOI":"10.3390\/rs11101172","type":"journal-article","created":{"date-parts":[[2019,5,16]],"date-time":"2019-05-16T11:21:22Z","timestamp":1558005682000},"page":"1172","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["The Two-Parts Step-by-Step Ionospheric Assimilation Based on Ground-Based\/Spaceborne Observations and Its Verification"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7989-7521","authenticated-orcid":false,"given":"Naifeng","family":"Fu","sequence":"first","affiliation":[{"name":"Shanghai Astronomical Observatory of Chinese Acdemy of Sciences, Shanghai 200030, China"},{"name":"University of Chinese Acdemy of Sciences, Beijing 100049, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Peng","family":"Guo","sequence":"additional","affiliation":[{"name":"Shanghai Astronomical Observatory of Chinese Acdemy of Sciences, Shanghai 200030, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mengjie","family":"Wu","sequence":"additional","affiliation":[{"name":"Shanghai Astronomical Observatory of Chinese Acdemy of Sciences, Shanghai 200030, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yong","family":"Huang","sequence":"additional","affiliation":[{"name":"Shanghai Astronomical Observatory of Chinese Acdemy of Sciences, Shanghai 200030, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xiaogong","family":"Hu","sequence":"additional","affiliation":[{"name":"Shanghai Astronomical Observatory of Chinese Acdemy of Sciences, Shanghai 200030, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zhenjie","family":"Hong","sequence":"additional","affiliation":[{"name":"College of Mathematics, Physics and Electronic Information Engineering, Wenzhou University, Wenzhou 325000, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,5,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1177","DOI":"10.1002\/qj.49711247414","article-title":"Analysis methods for numerical weather prediction","volume":"474","author":"Lorenc","year":"1986","journal-title":"Q. J. R. Meteorol. Soc."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1029\/2008RS004068","article-title":"Ionospheric dynamics and drivers obtained from a physics-based data assimilation model","volume":"44","author":"Scherliess","year":"2009","journal-title":"Radio Sci."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Huba, J.D., Krall, J., and Joyce, G. (2008, January 15\u201319). Three-dimensional modeling equatorial spread F. Proceedings of the AGU Fall Meeting Abstracts, San Francisco, CA, USA.","DOI":"10.1029\/2008GL033509"},{"key":"ref_4","first-page":"73","article-title":"The NCAR TIE-GCM: A community model of the coupled thermosphere\/ionosphere system","volume":"201","author":"Qian","year":"2013","journal-title":"Geophys. Monogr. Ser."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1856","DOI":"10.1016\/j.jastp.2008.01.015","article-title":"A new version of the NeQuick ionosphere electron density model","volume":"70","author":"Nava","year":"2008","journal-title":"J. Atmos. Sol.-Terr. Phys."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"599","DOI":"10.1016\/j.asr.2007.07.048","article-title":"International Reference Ionosphere 2007: Improvements and new parameters","volume":"42","author":"Bilitza","year":"2007","journal-title":"Adv. Space Res."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"18819","DOI":"10.1029\/1999JA000241","article-title":"Global core plasma model","volume":"105","author":"Gallagher","year":"2000","journal-title":"J. Geophys. Res."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"825","DOI":"10.1016\/S0273-1177(02)00038-8","article-title":"Plasmaspheric externsion of topside electron density profiles","volume":"29","author":"Gulyaeva","year":"2002","journal-title":"Adv. Space Res."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"929","DOI":"10.5047\/eps.2011.04.007","article-title":"Inter-hemispheric imaging of the ionosphere with the upgraded IRI-Plas model during the space weather storms","volume":"63","author":"Gulyaeva","year":"2011","journal-title":"Earth Planets Space"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Wu, M.J., Guo, P., Xu, T.L., Fu, N.F., Xu, X.S., Jin, H.L., and Hu, X.G. (2015). Data assimilation of plasmasphere and upper ionosphere using COSMIC\/GPS slant TEC measurements. Radio Sci., 50.","DOI":"10.1002\/2015RS005732"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Wu, M.J., Guo, P., Fu, N.F., Xu, T.L., Xu, X.S., Jin, H.L., and Hu, X.G. (2016). Topside corection of IRI by global modeling of ionospheric scale height using COSMIC radio occultation data. Space Phys., 121.","DOI":"10.1002\/2016JA022785"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Wu, M.J., Guo, P., Fu, N.F., Hu, X.G., and Hong, Z.J. (2018). Improvement of the IRI Model Using F2 Layer Parameters Derived From GPS\/COSMIC Radio Occultation Observations. J. Geophys. Res. Space Phys., 123.","DOI":"10.1029\/2018JA026092"},{"key":"ref_13","first-page":"1367","article-title":"A strategy for operational implementation of 4D-Var, using an incremental approach","volume":"120","author":"Courtier","year":"1994","journal-title":"Q. J. R. Meteor. Soc."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2588","DOI":"10.1175\/1520-0493(2000)128<2588:VAUSF>2.0.CO;2","article-title":"Variational analysis using spatial filters","volume":"128","author":"Huang","year":"2000","journal-title":"Mon. Weather Rev."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"RS1S06","DOI":"10.1029\/2002RS002854","article-title":"Development of the global assimilative ionospheric model","volume":"39","author":"Wang","year":"2004","journal-title":"Radio Sci."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"RS1S02","DOI":"10.1029\/2002RS002794","article-title":"Global Assimilation of Ionospheric Measurements (GAIM)","volume":"39","author":"Schunk","year":"2004","journal-title":"Radio Sci."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"8208","DOI":"10.1002\/2014GL062110","article-title":"Storm time ionosphere and plasmasphere structuring: SAMI3-RCM simulation of the 31 March 2001 geomagnetic storm","volume":"41","author":"Huba","year":"2014","journal-title":"Geophys. Res. Lett."},{"key":"ref_18","unstructured":"Fu, N., Guo, P., Wu, M., Hu, X., Huang, Y., and Hong, Z. (2019). Simulating and Assimilating Ionospheric Observations with Multisources. Adv. Space Res., 50."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Chen, C.H., Lin, C.H., Matsuo, T., Chen, W.H., Lee, I.T., Liu, J.Y., Lin, J.T., and Hsu, C.T. (2015). Ionospheric data assimilation with thermosphere-ionosphere-electrodynamics general circulation model and GPS-TEC during geomanetic storm conditions. J. Geophys. Res. Space Phys., 121.","DOI":"10.1002\/2015JA021787"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"433","DOI":"10.1002\/2016SW001363","article-title":"Regional 3-D ionospheric electron density specification on the basis of data assimilation of ground-based GNSS and radio occultation data","volume":"14","author":"Aa","year":"2016","journal-title":"Space Weather"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Gardner, L.C., Schunk, R.W., Scherliess, L., Sojka, J.J., and Zhu, L. (2014). Global Assimilation of Ionospheric Measurements-Gauss Markov model: Improved specifications with multiple data types. Space Weather, 20.","DOI":"10.1002\/2014SW001104"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"174","DOI":"10.1002\/ima.1850050214","article-title":"Imaging the ionosphere with the global positioning system","volume":"5","author":"Hajj","year":"1994","journal-title":"Int. J. Imaging Syst.Technol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"109","DOI":"10.1029\/97RS02615","article-title":"Tomography of the ionosphere: Four-dimensional simulations","volume":"33","author":"Howe","year":"1998","journal-title":"Radio Sci."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"RG1003","DOI":"10.1029\/2006RG000212","article-title":"History, current state, and future directions of ionospheric imaging","volume":"46","author":"Bust","year":"2008","journal-title":"Rev. Geophys"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"817","DOI":"10.1002\/2015JA021561","article-title":"Imaging the topside ionosphere and plasmasphere with ionospheric tomography using COSMIC GPS TEC","volume":"121","author":"Jayawardena","year":"2015","journal-title":"Geophys. Res. Space Phys."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"3759","DOI":"10.1109\/TGRS.2013.2275753","article-title":"Observing System Simulation Experiment Study on Imaging the Ionosphere by Assimilating Observations From Ground GNSS, LEO-Based Radio Occultation and Ocean Reflection, and Cross Link","volume":"52","author":"Yue","year":"2014","journal-title":"IEEE Trans. Geosci. Remote. Sens."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"251","DOI":"10.1007\/s10291-014-0433-1","article-title":"Estimation and analysis of GPS satelite DCB based on LEO observations","volume":"20","author":"Lin","year":"2014","journal-title":"GPS Solut."},{"key":"ref_28","unstructured":"Dang, Y., Wang, H., Zhao, W., and Bai, G. (2015). Research of the Characteristics of Inversiong Global Ionospheric with Fusing of BDS, GPS and GLONASS. J. Geod. Geodyn., 35."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Arikan, F., Nayir, H., Sezen, U., and Arikan, O. (2008). Estimation of single station interfrequency receiver bias using GPS-TEC. Radio Sci., 43.","DOI":"10.1029\/2007RS003785"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1002\/swe.20054","article-title":"Online, automatic, near-real time estimation of GPS-TEC: IONOLAB-TEC","volume":"11","author":"Sezen","year":"2013","journal-title":"Space Weather"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"275","DOI":"10.1002\/cjg2.836","article-title":"A calibrated tec methord for inversion of ionospheric GPS occultation data","volume":"49","author":"Wu","year":"2006","journal-title":"Chin. J. Geophys."},{"key":"ref_32","unstructured":"Yue, X., Schreiner, W.S., Kuo, Y.H., Hunt, D.C., and Rocken, C. (2013, January 16\u201320). GNSS Radio Occultation Technique and Space Weather Monitoring. Proceedings of the ION GNSS, Nashvill, TN, USA."}],"updated-by":[{"DOI":"10.3390\/rs11172006","type":"correction","label":"Correction","source":"publisher","updated":{"date-parts":[[2019,5,16]],"date-time":"2019-05-16T00:00:00Z","timestamp":1557964800000}}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/10\/1172\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,8,3]],"date-time":"2025-08-03T22:16:40Z","timestamp":1754259400000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/10\/1172"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,5,16]]},"references-count":32,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2019,5]]}},"alternative-id":["rs11101172"],"URL":"https:\/\/doi.org\/10.3390\/rs11101172","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,5,16]]}}}