ISSN 2070-7401 (Print), ISSN 2411-0280 (Online)
Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa


Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2019, Vol. 16, No. 6, pp. 221-234

Doppler spectrum of microwave signal backscattered by sea surface at small incidence angles

V.Yu. Karaev 1 , Yu.A. Titchenko 1 , E.M. Meshkov 1 , M.A. Panfilova 1 , M.S. Ryabkova 1 
1 Institute of Applied Physics RAS, Nizhny Novgorod, Russia
Accepted: 15.10.2019
DOI: 10.21046/2070-7401-2019-16-6-221-234
The spectral and energy characteristics of the backscattered microwave radar signal contain information about the parameters of the scattering surface. At present, the main information parameter is the backscattering radar cross section, which is determined by the geometry of the underlying surface. The information on the movement of the sea surface is contained in the Doppler spectrum of the reflected radar signal. In this paper, we consider the properties of the Doppler spectrum at small angles of incidence, when the quasi-specular backscattering mechanism dominates. The dependences of the width and shift of Doppler spectrum on the speed and direction of the wind and the incidence angle are constructed. It is shown that even for pure wind waves there is an ambiguous relationship between wind speed and Doppler spectrum parameters, which leads to ambiguity in solving the inverse problem. Numerical estimates showed that the parameters of antenna beam have a strong effect on the width and shift of the Doppler spectrum and this effect can be used to create simpler measurement schemes and develop new retrieval algorithms, which is especially important for orbital radars.
Keywords: width and shift of the Doppler spectrum, Kirchhoff approximation, two-scale model of scattering surface, small incidence angles, wind waves, antenna beam
Full text


  1. Bass F., Fuks I., Rasseyanie voln na statisticheski nerovnoi poverkhnosti (Wave scattering on a statistically rough surface), Moscow: Nauka, 1972, 424 p.
  2. Garnaker’yan A. A., Sosunov A. S., Radiolokatsiya morskoi poverkhnosti (Radar sensing of the sea surface), Rostov-on-Don: Izd. Rostovskogo universiteta, 1978, 144 p.
  3. Zubkovich S. G., Statisticheskie kharakteristiki radiosignalov, otrazhennykh ot zemnoi poverkhnosti (Statistical characteristics of radio signals reflected from the earth’s surface), Moscow: Sovetskoe radio, 1968, 224 p.
  4. Kanevsky M., Karaev V., Spektral’nye kharakteristiki radiolokatsionnogo SVCh-signala, otrazhennogo morskoi poverkhnost’yu pri malykh uglakh padeniya (Spectral characteristics of superhigh frequency (SHF) radar signal backscattered by the sea surface at small incidence angles), Izvestiya vysshikh uchebnykh zavedenii. Ser. “Radiofizika”, 1996, Vol. 39, No. 5, pp. 517–525.
  5. Karaev V., Balandina G., Modifitsirovannyi spektr volneniya i distantsionnoe zondirovanie (A modified wave spectrum and remote sensing of ocean), Issledovanie Zemli iz kosmosa, 2000, No. 5, pp. 1–12.
  6. Karaev V., Kanevsky M., Vosstanovlenie parametrov poverkhnostnogo volneniya po rezul’tatam radiolokatsionnykh izmerenii (Retrieval of sea surface parameters on radar data), Issledovanie Zemli iz kosmosa, 2008, No. 1, pp. 44–55.
  7. Karaev V., Panfilova M., Balandina G., Chu X., Vosstanovlenie dispersii naklonov krupnomasshtabnykh voln po radiolokatsionnym izmereniyam v SVCh-diapazone (Retrieval of the slope variance by microwave measurements), Issledovanie Zemli iz kosmosa, 2012, No. 4, pp. 62–77.
  8. Rozenberg A., Ostrovsky I., Kalmykov A., Sdvig chastoty pri rasseyanii radioizlucheniya vzvolnovannoi poverkhnost’yu morya (Frequency shift in the scattering of radio waves by an sea surface), Izvestiya vysshikh uchebnykh zavedenii. Ser. “Radiofizika”, 1966, Vol. 9, No. 2, pp. 234–240.
  9. Anderson C., Bonekamp H., Figa J., Wilson J., de Smet A., Stoffelen A., Verhoef A., Portabella M., Verspeek J., Duff C., Metop-A ASCAT Commissioning Quality Report, EUMETSAT OSI SAF SS3; EUMETSAT ASCAT Commissioning Team, 2009, 61 p.
  10. Ardhuin F., The SKIM Mission: a Pathfinder for Doppler Oceanography from Space, Doppler Oceanography from Space, Proc. Workshop, Brest, France, 10–12 Oct. 2018, 47 p., available at: (accessed 14.10.2019).
  11. Bass F., Fuks I., Kalmykov A., Ostrovsky I., Rosenberg A., Very high frequency radiowave scattering by a disturbed sea surface, IEEE Trans. Antennas Propagation, 1968, Vol. 16, No. 5, pp. 554–568.
  12. Chu X., He Y., Karaev V., Chen G., Relationships between Ku-band radar backscatter and integrated wind and waves parameters at low incidence angles, IEEE Trans. Geoscience and Remote Sensing, 2012, Vol. 50, No. 11, pp. 4599–4609, DOI: 10.1109/TGRS.2012.2191560.
  13. Cox C., Munk W., Measurement of the Roughness of the Sea Surface from Photographs of the Sun’s Glitter, J. Optical Society of America, 1954, Vol. 44, No. 11, pp. 838–850.
  14. Danilytchev M., Kutuza B., Nikolaev A., The Application of Sea Wave Slope Distribution Empirical Dependencies in Estimation of Interaction Between Microwave Radiation and Rough Sea Surface, IEEE Trans. Geoscience and Remote Sensing, 2009, Vol. 47, No. 2, pp. 652–661, DOI: 10.1109/TGRS.2008.2004410.
  15. Freilich M. H., Vanhoff B. A., The relation between winds, surface roughness, and radar backscatter at low incidence angles from TRMM Precipitation Radar measurements, J. Atmospheric and Oceanic Technology, 2003, Vol. 20, No. 4, pp. 549–562.
  16. Gohil B. S., Sarkar A., Agarwal V., A New Algorithm for Wind-Vector Retrieval from Scatterometers, IEEE Geoscience and Remote Sensing Letters, 2008, Vol. 5, No. 3, pp. 387–391, DOI: 10.1109/LGRS.2008.917129.
  17. Gommenginger C., Chapron B., Martin A., Marquez J., Brownsword C., Buck C., SEASTAR team, SEASTAR: a new mission concept for high-resolution imaging of ocean surface current and wind vectors from space, Doppler Oceanography from Space, Proc. Workshop, Brest, France, 10–12 Oct. 2018, 22 p., available at: (accessed 14.10.2019).
  18. Karaev V., Kanevsky M., Meshkov E., The effect of sea surface slicks on the Doppler spectrum width of a backscattered microwave signal, Sensors, 2008, Vol. 8, pp. 3780–3801.
  19. Nekrasov A., Khachaturian A., Abramov E., Popov D., Markelov O., Obukhovets V., Veremyev V., Bogachev V., Optimization of the airborne antenna geometry for the ocean surface scatterometric measurements, Remote Sensing, 2018, Vol. 10, No. 10, pp. 1–23, available at:
  20. Pidgeon V., The Doppler dependence of radar sea-return, J. Geophysical Research, 1968, Vol. 73, No. 4, pp. 1333–1341.
  21. Rodriguez E., Wineteer A., Perkovic-Martin D., DopplerScatt Results: What we have learned and implications for a Winds and Currents Mission, Doppler Oceanography from Space, Proc. Workshop, Brest, France, 10–12 Oct. 2018, 40 p., available at:
  22. Stoffelen A., Aaboe S., Calvet J.-Ch., Cotton J., De Chiara G., Saldana J. F., Mouche A., Portabella M., Scipal K., Wagner W., Scientific Developments and the EPS-SG Scatterometer, IEEE J. Selected Topics in Applied Earth Observations and Remote Sensing, 2017, Vol. 10, No. 5, pp. 2086–2097, DOI: 10.1109/JSTARS.2017.2696424.
  23. Valenzuela G., Theories for interaction of electromagnetic and oceanic waves: A review, Boundary Layer Meteorology, 1978, Vol. 13, pp. 61–86.
  24. Valenzuela G., Laing M., Study of Doppler spectra of radar sea echo, J. Research, 1970, Vol. 75, No. 3, pp. 551–563.
  25. Wentz F. J., A Simplified Wind Vector Algorithm for Satellite Scatterometers, J. Atmospheric and Oceanic Technology, 1991, Vol. 8, No. 5, pp. 697–704.
  26. Wentz F., Smith D., A model function for the ocean-normalized radar cross-section at 14 GHz derived from NSCAT observations, J. Geophysical Research, 1999, Vol. 104, No. C5, pp. 11499–11514.
  27. Wentz F. J., Peteheryh S., Thomas L., A model function for ocean radar cross-sections at 14.6 GHz, J. Geophysical Research, 1984, Vol. 89, pp. 3689–3704.
  28. Zhu D., Dong X., Yun R., Xu X., Recent advances in developing the CFOSAT Scatterometer, Proc. IGARSS’16, Beijing, China, 2016, pp. 5801–5803, DOI: 10.1109/IGARSS.2016.7730515.