{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,29]],"date-time":"2026-03-29T00:54:15Z","timestamp":1774745655544,"version":"3.50.1"},"reference-count":33,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2019,11,15]],"date-time":"2019-11-15T00:00:00Z","timestamp":1573776000000},"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>The paper describes a method for the accurate calibration of multi-channel SAR instruments, such as those required to support SAR polarimetry, single-pass interferometry and digital beam-forming (DBF), on the basis of dedicated SAR acquisitions containing reference targets with known properties. Unlike conventional approaches, the method is based entirely on the analysis of range-compressed raw data. It leverages the pulse-by-pulse analysis of amplitude, phase and delay variations observed within the range histories of reference targets to fully characterize and correct propagation direction dependent calibration issues such as those related to antenna pointing or antenna phase center positions. The fact that the approach does not require SAR image focusing in azimuth is especially relevant in the context of DBF, where individual channels need to be calibrated but are, by themselves, under-sampled. The calibration techniques presented are illustrated and validated using multi-channel polarimetric and single-pass interferometric SAR data acquired by DLR\u2019s airborne F-SAR and DBFSAR instruments.<\/jats:p>","DOI":"10.3390\/rs11222674","type":"journal-article","created":{"date-parts":[[2019,11,15]],"date-time":"2019-11-15T11:24:32Z","timestamp":1573817072000},"page":"2674","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Robust, Model-Based External Calibration of Multi-Channel Airborne SAR Sensors Using Range Compressed Raw Data"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9685-2977","authenticated-orcid":false,"given":"Marc","family":"J\u00e4ger","sequence":"first","affiliation":[{"name":"Microwaves and Radar Institute, German Aerospace Center (DLR), M\u00fcnchener Str. 20, 82234 We\u00dfling, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6833-4897","authenticated-orcid":false,"given":"Rolf","family":"Scheiber","sequence":"additional","affiliation":[{"name":"Microwaves and Radar Institute, German Aerospace Center (DLR), M\u00fcnchener Str. 20, 82234 We\u00dfling, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2118-5046","authenticated-orcid":false,"given":"Andreas","family":"Reigber","sequence":"additional","affiliation":[{"name":"Microwaves and Radar Institute, German Aerospace Center (DLR), M\u00fcnchener Str. 20, 82234 We\u00dfling, Germany"}]}],"member":"1968","published-online":{"date-parts":[[2019,11,15]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1107","DOI":"10.1109\/36.193786","article-title":"SAR calibration: An overview","volume":"30","author":"Freeman","year":"1992","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"606","DOI":"10.1109\/TGRS.2009.2031062","article-title":"The TerraSAR-X Mission and System Design","volume":"48","author":"Werninghaus","year":"2010","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"3317","DOI":"10.1109\/TGRS.2007.900693","article-title":"TanDEM-X: A Satellite Formation for High-Resolution SAR Interferometry","volume":"45","author":"Krieger","year":"2007","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"171","DOI":"10.1016\/j.jog.2010.01.001","article-title":"COSMO-SkyMed an existing opportunity for observing the Earth","volume":"49","author":"Covello","year":"2010","journal-title":"J. Geodyn."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"9","DOI":"10.1016\/j.rse.2011.05.028","article-title":"GMES Sentinel-1 mission","volume":"120","author":"Torres","year":"2012","journal-title":"Remote Sens. Environ."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"221","DOI":"10.5589\/m04-004","article-title":"An introduction to the RADARSAT-2 mission","volume":"30","author":"Morena","year":"2004","journal-title":"Can. J. Remote Sens."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"759","DOI":"10.1109\/JPROC.2012.2220511","article-title":"Very-High-Resolution Airborne Synthetic Aperture Radar Imaging: Signal Processing and Applications","volume":"101","author":"Reigber","year":"2013","journal-title":"Proc. IEEE"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Reigber, A., J\u00e4ger, M., Fischer, J., Horn, R., Scheiber, R., Prats, P., and Nottensteiner, A. (2011, January 24\u201329). System status and calibration of the F-SAR airborne SAR instrument. Proceedings of the Geoscience and Remote Sensing Symposium (IGARSS), 2011 IEEE International, Vancouver, BC, Canada.","DOI":"10.1109\/IGARSS.2011.6049357"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"690","DOI":"10.1109\/TGRS.2009.2033934","article-title":"TerraSAR-X Antenna Calibration and Monitoring Based on a Precise Antenna Model","volume":"48","author":"Bachmann","year":"2010","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"69","DOI":"10.5721\/ItJRS20104216","article-title":"Cosmo SkyMed: Antenna elevation pattern data evaluation","volume":"42","author":"Iorio","year":"2010","journal-title":"Ital. J. Remote Sens."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"994","DOI":"10.1109\/JSTARS.2015.2449239","article-title":"Independent verification of the Sentinel-1A system calibration","volume":"9","author":"Schwerdt","year":"2016","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Calabrese, D., Cricenti, A., Grimani, V., Scaranari, D., Vigliotti, R., Covello, F., and Marano, G. (2008, January 26\u201330). COSMO-SkyMed: Calibration & validation resources and activities. Proceedings of the 2008 IEEE Radar Conference, Rome, Italy.","DOI":"10.1109\/RADAR.2008.4721099"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"345","DOI":"10.5589\/m04-007","article-title":"RADARSAT-2 SAR image quality and calibration operations","volume":"30","author":"Luscombe","year":"2004","journal-title":"Can. J. Remote Sens."},{"key":"ref_14","unstructured":"Jirousek, M., D\u00f6ring, B., Rudolf, D., Raab, S., and Schwerdt, M. (2014, January 3\u20135). Development of the highly accurate DLR Kalibri transponder. Proceedings of the EUSAR 2014; 10th European Conference on Synthetic Aperture Radar, Berlin, Germany."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"487","DOI":"10.1109\/TGRS.2012.2201946","article-title":"High-Precision Assessment and Calibration of Polarimetric RADARSAT-2 SAR Using Transponder Measurements","volume":"51","author":"Touzi","year":"2013","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"139","DOI":"10.1109\/7.68156","article-title":"Accuracy of using point targets for SAR calibration","volume":"27","author":"Ulander","year":"1991","journal-title":"IEEE Trans. Aerosp. Electron. Syst."},{"key":"ref_17","unstructured":"Bickel, D., and Hensley, W. (1994, January 8\u201312). Interferometric SAR phase difference calibration: Methods and results. Proceedings of IGARSS \u201994-1994 IEEE International Geoscience and Remote Sensing Symposium, Pasadena, CA, USA."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"3074","DOI":"10.1109\/TGRS.2013.2269194","article-title":"Fully-Polarimetric High-Resolution 3-D Imaging with Circular SAR at L-Band","volume":"52","author":"Ponce","year":"2014","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"4462","DOI":"10.1109\/TGRS.2013.2282192","article-title":"Staggered SAR: High-resolution wide-swath imaging by continuous PRI variation","volume":"52","author":"Villano","year":"2013","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"6003","DOI":"10.1109\/TGRS.2013.2294353","article-title":"On the Processing of Very High Resolution Spaceborne SAR Data","volume":"52","author":"Scheiber","year":"2014","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_21","unstructured":"Curlander, J., and McDonough, R. (1991). Synthetic Aperture Radar: Systems and Signal Processing, Wiley."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Gabler, B., Kosc, A., and Limbach, M. (2018, January 9\u201314). Antenna Range Measurements for Airborne Remote Sensing Antennas. Proceedings of the European Conference on Antennas and Propagation (EuCAP), London, UK.","DOI":"10.1049\/cp.2018.1227"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Ruck, G. (1970). Radar Cross Section Handbook, Plenum Press.","DOI":"10.1007\/978-1-4899-5324-7"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"2179","DOI":"10.1109\/36.868876","article-title":"Coregistration of interferometric SAR images using spectral diversity","volume":"38","author":"Scheiber","year":"2000","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Boyd, S., Boyd, S., Vandenberghe, L., and Press, C.U. (2004). Convex Optimization, Cambridge University Press. Berichte \u00fcber Verteilte Messysteme.","DOI":"10.1017\/CBO9780511804441"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"525","DOI":"10.1080\/01431168608954707","article-title":"Ionospheric and tropospheric effects on synthetic aperture radar performance","volume":"7","author":"Quegan","year":"1986","journal-title":"Int. J. Remote Sens."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"519","DOI":"10.1109\/LGRS.2009.2020522","article-title":"Sparse Two-Dimensional Phase Unwrapping Using Regular Grid Methods","volume":"6","author":"Shanker","year":"2009","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"698","DOI":"10.1109\/TIP.2006.888351","article-title":"Phase unwrapping via graph cuts","volume":"16","author":"Valadao","year":"2007","journal-title":"IEEE Trans. Image Process."},{"key":"ref_29","unstructured":"Reigber, A., Nottensteiner, A., Limbach, M., J\u00e4ger, M., Kosc, A., Scheiber, R., Fischer, J., Catalan, D.L., M\u00fcller, G., and K\u00fcnemund, M. (2018, January 4\u20137). First Interferometric Trials with the Airborne Digital-Beamforming DBFSAR System. Proceedings of the European Conference on Synthetic Aperture Radar (EUSAR), Aachen, Germany."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"978","DOI":"10.1175\/1520-0426(1997)014<0978:OTEONS>2.0.CO;2","article-title":"On the extraction of near-surface index of refraction using radar phase measurements from ground targets","volume":"14","author":"Fabry","year":"1997","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_31","unstructured":"Krieger, G., Younis, M., Gebert, N., Huber, S., Bordoni, F., Patyuchenko, A., and Moreira, A. (2010, January 7\u201310). Advanced Concepts for High-Resolution Wide-Swath SAR Imaging. Proceedings of the European Conference on Synthetic Aperture Radar (EUSAR), Aachen, Germany."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"564","DOI":"10.1109\/TAES.2009.5089542","article-title":"Digital Beamforming on Receive: Techniques and Optimization Strategies for High-Resolution Wide-Swath SAR Imaging","volume":"45","author":"Gebert","year":"2009","journal-title":"IEEE Trans. Aerosp. Electron. Syst."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1109\/MGRS.2015.2437353","article-title":"Tandem-L: A highly innovative bistatic SAR mission for global observation of dynamic processes on the Earth\u2019s surface","volume":"3","author":"Moreira","year":"2015","journal-title":"IEEE Geosci. Remote Sens. Mag."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/22\/2674\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T13:34:51Z","timestamp":1760189691000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/22\/2674"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,11,15]]},"references-count":33,"journal-issue":{"issue":"22","published-online":{"date-parts":[[2019,11]]}},"alternative-id":["rs11222674"],"URL":"https:\/\/doi.org\/10.3390\/rs11222674","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,11,15]]}}}