Document Type : Research Note

Authors

1 Ph.D. Student. Iranian Space Research Center. Tehran.Iran .

2 Ph.D. Iranian Space Research Center. Tehran.Iran .

3 Assistant Professor .Iranian Space Research Center. Tehran.Iran

Abstract

Navigation errors in synthetic aperture radar (SAR) applications lead to phase errors in SAR echo signal and image quality degradation. Among different phase errors, zero and first order errors have no effect on image quality, while second and higher order terms are very important. The majority of second and higher order phase errors are due to initial alignment errors, and bias and random errors of inertial sensors. Integrated INS/GPS navigation systems are used for solving this problem. However, discontinuities in integrated navigation data lead to severe SAR image quality degradation. In this paper, the effect of different navigation approaches on SAR azimuth impulse response was studied and the importance of specially-designed algorithms to integrate INS and GPS was illustrated. Then, the proposed algorithm for navigation in SAR application was presented according to navigation errors behavior, and its benefit in azimuth impulse response, and imaging quality was illustrated. ‌‌

Keywords

[1]  Cumming, I.G. and Wong, F.H., Digital Processing of Synthetic Aperture Radar Data: Algorithms and Implementation, Artech House, Norwood, MA, USA, 2004.
[2]  Saeedi, J. and Alavi, S.M., "Improved Navigation-based Motion Compensation for LFMCW Synthetic Aperture Radar Imaging", Signal, Image and Video Processing, Vol. 10, pp. 405-412, 2016.
[3]  Doerry, A.W., "Motion Measurement for Synthetic Aperture Radar", Sandia National Laboratories, Sandia Report SAND2015-20818, New Mexico, USA, 2015.
[4]  Song, J.W.  and Park, C.G., "INS/GPS Integrated Smoothing Algorithm for Synthetic Aperture Radar Motion Compensation, Using an Extended Kalman Filter with a Position Damping Loop", International Journal of Aeronautical and Space Sciences, Vol. 18, pp. 118-128, 2017.
[5]  Kim, T. J., Fellerhoff, J.R., and Kohler, S.M., "An Integrated Navigation System, Using GPS Carrier Phase for Real-time Airborne/Synthetic Aperture Radar (SAR)", Navigation, Journal of the Institute of Navigation, Vol. 48, pp. 13-24, 2001.
[6]  Fang, J. and Gong, X., "Predictive Iterated Kalman Filter for INS/GPS Integration and Its Application to SAR Motion Compensation", IEEE Transactions on Instrumentation and Measurement, Vol. 59, pp. 909-915, 2009.
[7]  Song, J.W., Kang, C.W., Park, Y.B., Park, Y.G.J., and Park, C.G., "EGI/IMU Integration, Using Multiple IMUs and Error Damping Loop for SAR Motion Compensation", The ICCAS 2015-15th International Conference on Control, Automation and Systems, Busan, South Korea, 2015.
[8]  Buckreuss, S., "Motion Errors in an Airborne Synthetic Aperture Radar System", European Transactions on Telecommunications, Vol. 2, pp. 655-664, 1991.
[9]  Kim, T.J., "Motion Measurement for High-accuracy Real-time Airborne SAR", Radar Sensor Technology VIII and Passive Millimeter-Wave Imaging Technology VII, Vol. 5410, pp. 36-50, 2004.
[10] Kazerooni, M. and Khodaei, M., "Combination of RDA with PGA Method to Appropriate Image Formation on SAR with Ballistic Motion", Journal of Radar, Vol. 4, pp. 14-30, 2016.
[11]   Titterton, D.H. and Weston, J.L., Strapdown Inertial Navigation Technology, The Institution of Electrical Engineers, Herts, United Kingdom 2004.
[12]   Abbasi, P. and Haeri, M., "Accuracy Improvement of GPS/INS Navigation System, Using Extended Kalman Filter", The 6th International Conference on Control, Instrumentation and Automation (ICCIA), Sanandaj, Kurdistan, Iran, 2019.
[13]   Menna, B.V., Villar, S.A., Rozenfeld, A., and Acosta, G.G., "GPS Aided Strapdown Inertial Navigation System for Autonomous Robotics applications", The XVII Workshop on Information Processing and Control (RPIC), Mar de Plata, Argentina, 2017.
[14]   Wang, M., Wu, W., Zhou, P., and He, X., "State Transformation Extended Kalman Filter for GPS/SINS Tightly Coupled Integration", GPS Solutions, Vol. 22, pp. 112-127, 2018.
[15]   Makarem, H., Mahmudabadi, V.Ch., Parvaresh, A., and Shamsedini, M., "Extraction and Validation of Equations Related to the Effect of Low Frequency and High Frequency Errors on the Accuracy of the Navigation System in Artificial Aperture Radar", The 17th International Conference of Iranian Aerospace Society, Islamic Azad University, Science and Research Branch, Thehran, Iran, 2018.
[16]   Shin, E.-H. and El-Sheimy, N., "Accuracy Improvement of Low Cost INS/GPS for Land Applications", The US institute of navigation, National Technical Meeting, San Diego, CA, USA, 2002.