KIGAMKIGAM 지반변형 모니터링을 위한 GROUND-BASED SAR 개발 지반변형 모니터링을 위한 GROUND-BASED SAR 개발 한국지구시스템공학회 조성준 (1), 이훈열 (2), 성낙훈 (1), 김정호 (1) (1)한국지질자원연구원 지반탐사연구실 (2)강원대학교 지구물리학과

Engineering geophysics KIGAMKIGAM Agenda Introduction of SAR and GB-SAR Hardware configuration of GB-SAR Acquisition software for GB-SAR SAR Focusing and Interferometry Feasibility test Conclusion

Engineering geophysics KIGAMKIGAM Radar Radio Detection and Ranging WW II, US army. Military use measure backscattered amplitude and distance to target High power, sharp pulse -> low power, FM-CW chirp signal Navigation radar Weather radar Ground Penetrating Radar Imaging radar cf) LIDAR (Light detection and Ranging)

Engineering geophysics KIGAMKIGAM Imaging Radar Different Eyes microwave, UHF, VHF surface roughness and dielectric constant Microwave Ranging All-weather Cloud-free Side-looking Active System Day and night imaging independent of solar illumination

Engineering geophysics KIGAMKIGAM SAR(Synthetic Aperture Radar)  Optics : Diameter of the lens or mirror. The larger the aperture, the more light a telescope collects. 2.4m Hubble Space Telescope 10m Keck, Hawaii 16.4m VLT (Very Large Telescope), Chile 50m Euro50 (extremely large T.) 100m OWL (OverWhelmingly Large T.)  Euro50 Aperture:

Engineering geophysics KIGAMKIGAM Real vs. Synthetic Aperture Real Aperture :  resolution ~ Rλ/L Synthetic Aperture:  resolution ~ L/2  Irrespective of R

Engineering geophysics KIGAMKIGAM Range Compression  For ERS-1/2,  Pulse duration (T): 37.1  s  Bandwidth : 15.5 MHz  Half power width of autocorrelation function:  s  Pulse Compression Ratio: 575 (ERS-1/2)  Ground Range Resolution: 12.5 m  Matched Filtering  Chirp autocorrelation Function  Linear Chirp Signal

Engineering geophysics KIGAMKIGAM SAR Focusing – Point Target range azimuth  original  After range compression  After migration  After azimuth compression

Engineering geophysics KIGAMKIGAM GB-SAR GB-SAR: Ground-Based Synthetic Aperture Radar –Synthetic Aperture Radar Imaging Radar Azimuth aperture synthesis –Ground-Based Fairly versatile system configuration –Multiple frequency (L, C, X, Ku, Ka, etc) –Full Polarization (VV, VH, HV, HH) Ultimate SAR focusing –Zero Doppler centroid (stationary vehicle during Tx/Rx) –Accurate estimation of Doppler rate from geometry Topography Mapping: Cross-Track InSAR or Delta-K InSAR Surface Motion: Zero-baseline and short atmospheric path for Temporal Coherency, DInSAR and PSInSAR Useful for new SAR concept design

Engineering geophysics KIGAMKIGAM State of the art of GB-SAR LISA SAR (Italy) GB-POLInSAR (Australia) GB-SAR (Japan)

Engineering geophysics KIGAMKIGAM GB-SAR System(KIGAM-KNU)

Engineering geophysics KIGAMKIGAM System Configuration

Engineering geophysics KIGAMKIGAM VNA(Vector Network Analyzer)  Stepped frequency  Both of Tx and Rx  Flexibility

Engineering geophysics KIGAMKIGAM Antenna H-Pol radiation pattern Dual-Polarimetric Square Horn Antenna Frequency(GHz)5.0~5.6 Beam Width E-Plane(deg)15(nominal) 12.1~13 H-Plane(deg)15(nominal)15.5~17.5 Gain(dBi)20(nominal)20.5 min.(20.5~21.8) VSWR1.5 max.1.4 max. Isolation 35dB 이하 50dB 이하 Weight(kg)4 max.3.1 max. Input Impedance(Ω)50

Engineering geophysics KIGAMKIGAM Rail and motion control  2 축 motion  6m rail (2m X 3)  Home and limit switch  Micro step motor  측정장치 일체형  NI motion controller

Engineering geophysics KIGAMKIGAM Amp and RF switch  Operating Freq.: 2~6 GHz  Power Gain: 34 dB  Maximum input: 6 dBm  Operation Freq.: ~20GHz  GPIB interface  3 중 1X2 SPDT

Engineering geophysics KIGAMKIGAM Acquisition software Start Initialize all system Move to start position Acquisition Call cal:VV:Switching: Call cal:VH:Switching: Call cal:HV:Switching: Call cal:HH:Switching End Move or Stop Callibration Save data

Engineering geophysics KIGAMKIGAM SAR Focusing Algorithms AlgorithmsAdvantageDisadvantageUsage Range-Doppler or ω-k Widely used for SAR Memory inefficiency for partial-focusing Near Range (full-focusing) Deramp-FFT Efficient in memory and CPU time Distortion in near range Far Range (partial-focusing) Time Domain Exact everywhere Time consumingEverywhere

Engineering geophysics KIGAMKIGAM GB-SAR Resolutions (a) Full Focusing (b) Partial Focusing Range resolution:

Engineering geophysics KIGAMKIGAM GB-InSAR Configuration DInSAR Cross-Track InSAR Delta-K InSAR Cross-Track and Delta-K InSAR  DInSAR with range change  Cross-Track InSAR

Engineering geophysics KIGAMKIGAM KIGAM Test T1 Range: Center frequency=5.3GHz Bandwidth=200MHz Sample=1601 Power=33dBm (2W) Azimuth: Scan length=5m Step=5cm Sample=101 T2: Temporal baseline of 20minutes (DInSAR) T3: Spatial baseline of -30cm vertical (InSAR DEM) T4: Frequency shift of -10MHz (Delta-K InSAR)

Engineering geophysics KIGAMKIGAM Image Area

Engineering geophysics KIGAMKIGAM VV

Engineering geophysics KIGAMKIGAM VH

Engineering geophysics KIGAMKIGAM DInSAR (T2-T1) VV

Engineering geophysics KIGAMKIGAM Automatic Acquisition with 2cm Step, :22pm- 4:20am, A1~A9 HH VV

Engineering geophysics KIGAMKIGAM Conclusion A GB-SAR system was developed, tested, and waiting for applications. Optimal GB-SAR focusing algorithms were tested. Cross-Track and Delta-K InSAR were tested. DInSAR or PSInSAR were tested: Phase stability of 1° (0.1mm range) was achieved for several hours for stable reflectors, rendering phase change of 10 ° meaningful (1mm range accuracy for DInSAR). GB-SAR can be used for various applications such as: –Safety monitoring of geohazard area –Safety monitoring of artificial structure –Microwave backscattering properties of target –New SAR system concept design More robust GB-SAR system optimized to a specific application will be developed.->accurate positioning, cost effective system