Advertisement

Limitations of the SEASAT SAR in High Sea States

  • F. M. Monaldo
  • R. C. Beal

Abstract

Although the spectral analysis of SEASAT SAR imagery has shown qualitatively good agreement with independent surface spectral measurements, quantitative two-dimensional ocean energy spectra from SAR imagery remain an elusive goal. The exact relationship between the ocean wave energy spectrum and the corresponding SAR image spectrum constitutes the central problem of much recent research. This chapter outlines a systematic approach to estimation of ocean wave spectra from SAR image spectra based on recent analysis of SEASAT SAR digital data. The effect of the various wave-imaging mechanisms, the stationary scatterer resolution response function, and the moving scatterer resolution response function are considered. Corrections for the latter two effects are applied to actual SAR image spectra. Particular attention is paid to the degradation of the azimuth component of SAR spectra in moderate to high sea states by the moving scatterers, which limit the ability of the SAR to image azimuthtraveling waves. This effect is quantitatively modeled and predictions of the model are shown to agree with actual SAR spectra. Corrections for the moving scatterer resolution response function are shown to result in better estimation of the position of remote storm sources.

Keywords

Synthetic Aperture Radar Modulation Transfer Function Ocean Wave Synthetic Aperture Radar Data Spectral Modulation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Alpers, W. R., and K. Hasselmann (1978): The two-frequency microwave technique for measuring ocean-wave spectra from an airplane or satellite. Boundary-Layer Meteorol 13, 215–230.CrossRefGoogle Scholar
  2. Alpers, W. R., and C. L. Rufenach (1979): The effect of orbital velocity motions on synthetic aperture radar imagery of ocean waves. IEEE Trans. Antennas Propag. AP-27, 685–690.CrossRefGoogle Scholar
  3. Alpers, W. R., D. B. Ross, C. L. Rufenach (1981): On the detectability of ocean surface waves by real and synthetic aperture radar. J. Geophys. Res. 86, 6481–6498.CrossRefGoogle Scholar
  4. Beal, R. C. (1980): Spaceborne imaging radar: ocean wave monitoring. Science 208, 1373–1375.CrossRefGoogle Scholar
  5. Beal, R. C., W.J. Geckle, A. G. Goldfinger, and D. G. Tilley (1981): System calibration strategies for spaceborne synthetic aperture radar. JHU/APL Report CP-084, December.Google Scholar
  6. Beal, R. C, D. G. Tilley, and F. M. Monaldo (1983): Large and small scale spatial evolution of digitally processed ocean wave spectra from the Seasat synthetic aperture radar.J. Geophys. Res. 88, 1761–1778.CrossRefGoogle Scholar
  7. Bendat, J. S., and A. G. Piersol (1971): Random Data: Analysis and Measurement Procedures, Wiley-Interscience, New York.MATHGoogle Scholar
  8. Bjerkaas, A. W., and F. W. Riedel (1979): Proposed model of the elevation spectrum of a wind roughened sea surface. JHU/APL TG-1328, Johns Hopkins University/Applied Physics Laboratory, NTIS ADA 08342617.Google Scholar
  9. Elachi, C., and W. E. Brown, Jr. (1977): Models of radar imaging of the ocean surface waves. IEEE Trans. Antennas Propag. AP-27, 84–95.CrossRefGoogle Scholar
  10. Evans, D. D., and O. H. Shemdin (1980): An investigation of the modulation of capillary and short gravity waves in the open ocean. J. Geophys. Res. 85, 5019–5024.CrossRefGoogle Scholar
  11. Goldfinger, A. (1980): Seasat SAR processing signatures: Point targets. JHU/APL Technical Report CP-078, Johns Hopkins University/Applied Physics Laboratory.Google Scholar
  12. Gonzalez, F. L, R. C. Beal, W. E. Brown, P. S. DeLeonibus, J. W. Sherman, III, J. F. R. Gower, D. Lichy, D. B. Ross, C. L. Rufenach, and R. A. Shuchman (1979): Seasat synthetic aperture radar: Ocean wave detection capabihties. Science 204, 1418–1421.CrossRefGoogle Scholar
  13. Keller, W. C., and J. W. Wright (1975): Microwave scattering and straining of wind generated waves. Radio Sci. 10, 139–147.CrossRefGoogle Scholar
  14. Larson, T. R., L. L Moskowitz, and J. W. Wright (1956): A note on SAR imagery of the ocean. IEEE Trans. Antennas Propag. AP-24, 393–394.CrossRefGoogle Scholar
  15. Monaldo, F. M., and R. S. Kasevich (1981): Optical determination of short-wave modulation by long ocean gravity waves. IEEE Trans. Geosci. Remote Sensing GE-20, 254–259.CrossRefGoogle Scholar
  16. Phillips, O. M. (1981): The structure of short gravity waves on the ocean surface. Spaceborne Synthetic Aperture Radar for Oceanography (R. C. Beal, P. S. DeLeonibus, and I Katz, eds.), Johns Hopkins Press, Baltimore, 24–31.Google Scholar
  17. Plant, W. J., W. C. Keller, and J. W. Wright (1978): Modulation of coherent microwave backscatter.J.Geophys. Res. 83, 1347–1352.CrossRefGoogle Scholar
  18. Raney, R. K. (1971): Synthetic aperture imaging radar and moving targets.IEEE Trans. Aerosp. Electron. Syst. AES-7, 499–505.CrossRefGoogle Scholar
  19. Raney, R. K. (1982): Synthetic aperture radar imaging of the sea. 1982 International Geoscience and Remote Sensing Symposium Digest, WA-2, IEEE Catalog No. 82 CH14723–6.Google Scholar
  20. Swift, C. T., and L. R. Wilson (1979): Synthetic aperture radar imaging of ocean waves. IEEE Trans. Antennas Propag. AP-27, 725–729.CrossRefGoogle Scholar
  21. Townsend, W. F. (1980): An initial assessment of the performance achieved by the Seasat-1 radar altimeter. IEEE J. Ocean. Eng. OE-5, 80–92.CrossRefGoogle Scholar
  22. Tyler, G. L., C. C. Teague, R. H. Stewart, A. M. Peterson, W. H. Münk, and J. W. Joy (1974): Wave directional spectra from synthetic aperture observations of radio scatter.Deep-Sea Res. 21, 989–1016.Google Scholar
  23. Valenzuela, G. R., and J. W. Wright (1979): Modulation of short gravity-capillary waves by longer-scale periodic flows-A higher order theory. Radio Sci. 14, 1099–1110.CrossRefGoogle Scholar
  24. Wright, J. W. (1966): Backscattering from capillary waves with application to sea clutter. IEEE Trans. Antennas Propag. AP-14, 749–754.CrossRefGoogle Scholar
  25. Wright, J. W., W. J. Plant, W. C. Keller, and W. L. Jones (1980): Ocean wave-radar modulation transfer functions from the West Coast Experiment.J. Geophys. Res. 85, 4957–4966.CrossRefGoogle Scholar

Copyright information

© Plenum Press, New York 1986

Authors and Affiliations

  • F. M. Monaldo
    • 1
  • R. C. Beal
    • 1
  1. 1.Applied Physics LaboratoryThe Johns Hopkins UniversityLaurelUSA

Personalised recommendations