{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,13]],"date-time":"2026-02-13T09:10:06Z","timestamp":1770973806645,"version":"3.50.1"},"reference-count":38,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2022,1,26]],"date-time":"2022-01-26T00:00:00Z","timestamp":1643155200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000181","name":"Air Force Office of Scientific Research","doi-asserted-by":"publisher","award":["AFOSR\/RTB1"],"award-info":[{"award-number":["AFOSR\/RTB1"]}],"id":[{"id":"10.13039\/100000181","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Sporadic-E (Es) occurrence rates from Global Position Satellite radio occultation (GPS-RO) measurements have shown to vary by a factor of five between studies, motivating the need for a comparison with ground-based measurements. In an attempt to find accurate GPS-RO techniques for detecting Es formation, occurrence rates derived using five previously developed GPS-RO techniques are compared to ionosonde measurements over an eight-year period from 2010\u20132017. GPS-RO measurements within 170 km of a ionosonde site are used to calculate Es occurrence rates and compared to the ground-truth ionosonde measurements. The techniques are compared individually for each ionosonde site and then combined to determine the most accurate GPS-RO technique for two thresholds on sporadic-E intensity: no lower limit and fbEs \u22653 MHz. Overall, the YuS4 method shows the closest agreement with ionosonde measurements for total Es occurrence rates without a lower limit on intensity, while the phase-based Chu technique shows the closest agreement for fbEs \u22653 MHz. This analysis demonstrates that the variation in GPS-RO derived sporadic-E occurrence rates is due to varying thresholds on the sporadic-E intensities in terms of fbEs.<\/jats:p>","DOI":"10.3390\/rs14030581","type":"journal-article","created":{"date-parts":[[2022,1,26]],"date-time":"2022-01-26T03:33:32Z","timestamp":1643168012000},"page":"581","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["A Comparison of Sporadic-E Occurrence Rates Using GPS Radio Occultation and Ionosonde Measurements"],"prefix":"10.3390","volume":"14","author":[{"given":"Rodney A.","family":"Carmona","sequence":"first","affiliation":[{"name":"Space Vehicles Directorate, Air Force Research Laboratory, Kirtland AFB, NM 87117, USA"}]},{"given":"Omar A.","family":"Nava","sequence":"additional","affiliation":[{"name":"Department of Engineering Physics, Air Force Institute of Technology, Wright-Patterson AFB, OH 45433, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0766-1701","authenticated-orcid":false,"given":"Eugene V.","family":"Dao","sequence":"additional","affiliation":[{"name":"Space Vehicles Directorate, Air Force Research Laboratory, Kirtland AFB, NM 87117, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3495-6372","authenticated-orcid":false,"given":"Daniel J.","family":"Emmons","sequence":"additional","affiliation":[{"name":"Department of Engineering Physics, Air Force Institute of Technology, Wright-Patterson AFB, OH 45433, USA"}]}],"member":"1968","published-online":{"date-parts":[[2022,1,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"401","DOI":"10.1016\/0021-9169(89)90122-0","article-title":"Recent work on mid-latitude and equatorial sporadic-E","volume":"51","author":"Whitehead","year":"1989","journal-title":"J. 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