Estimation of Doppler Centroid Frequency Using SAR Imaging Geometry for RISAT-2
Phani Madhav Yannam1, P.V. Jayasri2, K.Rameshbabu3, Suraj Bharath.Chada4
1Phani Madhav Yannam, ECE, Professor, Hyderabad Institute of Technology and Management, JNTUH, Hyderabad, India.
2P.V. Jayasri, Department of Space, Govt of Hyderabad, India.
3Dr K Rameshbabu, ECE, Professor, Hyderabad Institute of Technology and Management, JNTUH, Hyderabad, India.
4Suraj Bharath. Chada, ECE, Professor, Hyderabad Institute of Technology and Management, JNTUH, Hyderabad, India.
Manuscript received on November 22, 2012. | Revised Manuscript received on December 11, 2012. | Manuscript published on December 30, 2012. | PP: 43-51 | Volume-2, Issue-2, December 2012. | Retrieval Number: B0829112212 /2012©BEIESP
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© The Authors. Blue Eyes Intelligence Engineering and Sciences Publication (BEIESP). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Abstract: Synthetic Aperture Radar (SAR) is an active microwave sensor which uses coherent imaging techniques to produce high-resolution images of the ground. One of the essential part of SAR Data Processing is the estimation of the Doppler parameters of the received data i.e., Doppler centroid frequency, Fdc. The methodology involves sequence of coordinate rotations and translations to get the radar beam’s “view vector” into ECI coordinates. With satellite and target positions and velocities expressed in the same coordinate system, the velocities are projected along the beam vector to find the relative velocity, and then calculate Doppler centroid frequency. The orbit of RISAT-2 is low inclination non-polar, non-sun synchronous orbit and the image data format is different. So, in order to implement the procedure for RISAT-2, the satellite attitude i.e., yaw and pitch are derived from squint angle available in Auxiliary file to arrive at the slant range from the target. A module to calculate the satellite hour angle for both ascending and descending pass has been successfully implemented and integrated into the algorithm which is critical in calculating Fdc.
Keywords: SAR, SAR Geometry, Doppler Centroid Frequency (Fdc), Imaging Range, RISAT-2