{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,3]],"date-time":"2026-03-03T16:08:34Z","timestamp":1772554114473,"version":"3.50.1"},"reference-count":21,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2019,12,7]],"date-time":"2019-12-07T00:00:00Z","timestamp":1575676800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Radio frequency interference (RFI) is a well-documented problem for passive remote sensing of the Earth at L-band even though the measurements are made in the protected band at 1.413 GHz. Consequently, filtering for RFI is an important early step in the processing of measurements made by the SMAP (Soil Moisture Active\/Passive) radiometer. However, the filtered data still include regions with suspiciously high antenna temperatures. One possible cause of these \u201chot spots\u201d is interference not fully detected during RFI filtering. This paper presents evidence supporting this hypothesis and describes an algorithm to identify these \u201chot spots\u201d so that they can be removed from the measurements. The impact of removing these \u201chot spots\u201d is generally small, but evidence is presented that the brightness temperature and soil moisture improve when the hot spots are removed.<\/jats:p>","DOI":"10.3390\/rs11242935","type":"journal-article","created":{"date-parts":[[2019,12,9]],"date-time":"2019-12-09T05:54:51Z","timestamp":1575870891000},"page":"2935","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Detection of Residual \u201cHot Spots\u201d in RFI-Filtered SMAP Data"],"prefix":"10.3390","volume":"11","author":[{"given":"Yan","family":"Soldo","sequence":"first","affiliation":[{"name":"NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20770, USA"},{"name":"Universities Space Research Association, 7178 Columbia Gateway drive, Columbia, MD 21046, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9335-0741","authenticated-orcid":false,"given":"David","family":"Le Vine","sequence":"additional","affiliation":[{"name":"NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20770, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Paolo","family":"de Matthaeis","sequence":"additional","affiliation":[{"name":"NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20770, USA"},{"name":"Universities Space Research Association, 7178 Columbia Gateway drive, Columbia, MD 21046, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,12,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"704","DOI":"10.1109\/JPROC.2010.2043918","article-title":"The soil moisture active passive (SMAP) mission","volume":"98","author":"Entekhabi","year":"2010","journal-title":"Proc. IEEE"},{"key":"ref_2","unstructured":"Entekhabi, D., Yueh, S., O\u2019Neill, P.E., Kellogg, K.H., Allen, A., Bindlish, R., Brown, M., Chan, S., Colliander, A., and Crow, W.T. (2014). SMAP Handbook-soil Moisture Active Passive: Mapping Soil Moisture and Freeze\/Thaw From Space, JPL Publication."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"761","DOI":"10.1109\/TGRS.2013.2281266","article-title":"Radio-frequency interference mitigation for the soil moisture active passive microwave radiometer","volume":"52","author":"Piepmeier","year":"2014","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Misra, S., Johnson, J., Aksoy, M., Peng, J., Bradley, D., O\u2019Dwyer, I., Padmanabhan, S., Dawson, D., Chazanoff, S., and Latham, B. (2013, January 21\u201326). SMAP RFI mitigation algorithm performance characterization using airborne high-rate direct-sampled SMAPVEX 2012 data. Proceedings of the IEEE International Geoscience and Remote Sensing Symposium-IGARSS, Melbourne, Australia.","DOI":"10.1109\/IGARSS.2013.6721087"},{"key":"ref_5","unstructured":"International Telecommunication Union (2016). Radio Regulations, International Telecommunication Union."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1954","DOI":"10.1109\/TGRS.2016.2631978","article-title":"SMAP L-band microwave radiometer: Instrument design and first year on orbit","volume":"55","author":"Piepmeier","year":"2017","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"6854","DOI":"10.1109\/TGRS.2018.2844127","article-title":"Location of Radio-Frequency Interference Sources Using the SMAP L-Band Radiometer","volume":"56","author":"Soldo","year":"2018","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Soldo, Y., Le Vine, D.M., Bringer, A., Mohammed-Tano, P.M., de Matthaeis, P., Piepmeier, J.R., and Johnson, J.T. (2018, January 22\u201327). Recent Advances in SMAP RFI Processing. Proceedings of the Geoscience and Remote Sensing Symposium (IGARSS), 2018 IEEE International, Valencia, Spain.","DOI":"10.1109\/IGARSS.2018.8518891"},{"key":"ref_9","unstructured":"Piepmeier, J., Mohammed, P., De Amici, G., Kim, E., Peng, J., and Ruf, C. (2016). Algorithm Theor. Basis Doc., SMAP L1B Radiom. Bright. Temp. Data Product.: L1B_TB (Rev. B)."},{"key":"ref_10","unstructured":"(Mathworks, 2012). Matlab\u00ae-Graphics-R2012a, Mathworks."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"249","DOI":"10.3989\/scimar.03621.19K","article-title":"A new space technology for ocean observation: the SMOS mission","volume":"76","author":"Font","year":"2012","journal-title":"Sci. Mar."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Le Vine, D.M., Lagerloef, G.S.E., Ruf, C., Wentz, F., Yueh, S., Piepmeier, J., Lindstrom, E., and Dinnat, E. (2012, January 5\u20139). Aquarius: The instrument and initial results. Proceedings of the 2012 IEEE 12th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment (MicroRad), Frascati, Italy.","DOI":"10.1109\/MicroRad.2012.6185226"},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Kristensen, S.S., Balling, J., Skou, N., and S\u00f8bj\u0153rg, S.S. (2012, January 22\u201327). RFI in SMOS data detected by polarimetry. Proceedings of the IEEE International Geoscience and Remote Sensing Symposium, Munich, Germany.","DOI":"10.1109\/IGARSS.2012.6350593"},{"key":"ref_14","unstructured":"Chan, S., Njoku, E., and Colliander, A. (2014). Algorithm Theoretical Basis Document, Level 1C Radiometer Data Product (Rev. A), Jet Propulsion Laboratory."},{"key":"ref_15","unstructured":"O\u2019Neill, P., Binlish, R., Chan, S., Njoku, E., and Jackson, T. (2018). Algorithm Theoretical Basis Document, Level 2  3 Soil Moisture (Passive) Data Product (Rev. D), Jet Propulsion Laboratory."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Soldo, Y., de Matthaeis, P., and Le Vine, D.M. (2016). L-band RFI in Japan. Radio Frequency Interference (RFI), IEEE.","DOI":"10.1109\/RFINT.2016.7833542"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Bringer, A., Johnson, J.T., Mohammed, P.N., and Piepmeier, J.R. (2017, January 23\u201328). Performance of SMAP radiometer RFI detection algorithms and analysis of residual RFI sources. Proceedings of the IEEE International Geoscience and Remote Sensing Symposium (IGARSS), Fort Worth, TX, USA.","DOI":"10.1109\/IGARSS.2017.8127185"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"4220","DOI":"10.1109\/TGRS.2017.2690406","article-title":"L-band RFI detected by SMOS and Aquarius","volume":"55","author":"Soldo","year":"2017","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_19","unstructured":"(2011). SMOS Project: SMOS Level 2 Processor Soil Moisture Algorithm Theoretical Basis Document, ARGANS\/ACRI. Revision 5, Sections 3, Issue 3."},{"key":"ref_20","first-page":"4574","article-title":"Aquarius RFI detection and mitigation algorithm: Assessment and examples","volume":"52","author":"Ruf","year":"2013","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"515","DOI":"10.1109\/LGRS.2012.2211993","article-title":"A study of SMOS RFI over North America","volume":"10","author":"Aksoy","year":"2012","journal-title":"IEEE Geosci. Remote. Sens. Lett."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/24\/2935\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T13:40:16Z","timestamp":1760190016000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/24\/2935"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,12,7]]},"references-count":21,"journal-issue":{"issue":"24","published-online":{"date-parts":[[2019,12]]}},"alternative-id":["rs11242935"],"URL":"https:\/\/doi.org\/10.3390\/rs11242935","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,12,7]]}}}