Full Polarimetric Synthetic Aperture Radar (SAR) Data for Ionosphere Observation - A Comparative Study Shradha Mohanty 1 *, Gulab Singh 1 1 CSRE, IIT Bombay *Visiting Researcher at ISR, Boston College 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 1
Overview: Ionospheric Scintillation Effects on satellites Observation: GPS Measurements: SAR as a proxy SAR for scintillation identification Indices SAR RCS Comparison 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 2
Scintillation: Cloud of Electrons Interaction of ionosphere with radio waves alters the wave properties Background electrons Short-duration, high-intensity Ionospheric Scintillations High priority due to its significant impact on satellite radio, GPS communication, etc. Observed in low-frequency (L- and P-bands) SAR signals 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 3
Effects on GPS and SAR: 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 4
Effects on GPS and SAR: Defocusing Inaccurate phase calculation Azimuthal streaking RCS instability Rufenach, 1975 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 5
Case Study Satellite/Sensor Frequency of Operation Bandwidth Revisit, No. of cycles/day Mode Width x Length ALOS-2 / PALSAR-2 1.27 GHz 28 MHz 14 days, 15 Full Pol [HH+HV+VH+VV] 30 km x 70 km Resolution 10 m (8.7 m x 5.3 m) Data Level Orbit 1.1 Single Look Complex Height, inclination 698 km, 97.9 Date Time Sun-synchronous, Right-looking 23-Mar-2015, 31-Oct-2016 18:54 18:59 hrs (UTC) 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 6
Case Study 23-Mar-2015 2000 km N 31-Oct-2016 B B 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 7
Case Study 23-Mar-2015 2000 km N 31-Oct-2016 B B 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 8
Case Study 23-Mar-2015 2000 km N 31-Oct-2016 B B 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 9
Scintillation Observations: GPS CALCUTTA TIRUNELVELI RAJKOT CALCUTTA TIRUNELVELI 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 10
Scintillation Observations: GPS RAJKOT TIRUNELVELI RAJKOT CALCUTTA TIRUNELVELI 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 11
One-way S4 Vertically integrated Strength of Turbulence Propagation angle Reduced slant propagation distance Spectral slope Geometry and propagation factor 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 12
Avg. CkL at Tirunelveli 1.45 x 10 34 Avg. CkL at Rajkot 1.72 x 10 33 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 13
Scintillation Observations: SAR S4 measurements: Image Contrast (C d ) RCS Enhancement CkL measurements: Side Lobe Function (SLF) of Corner Reflector Image Clutter (Belcher and Cannon, 2014) (Mannix et al., 2017) (Belcher et al., 2017) 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 14
Scintillation Observations: SAR S4 measurements: Image Contrast (C d ) RCS Enhancement 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 15
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SAR for Scintillation Identification: Motivation Image pairs with uniform background Satellite s viewing geometry details Need for simple identification options Coefficient of variance (CoV) Local homogeneity/heterogeneity Speckle filtering 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 17
CoV of SAR Intensities at different polarizations HH HV VV VH 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 18
CoV of other SAR quantities TOTAL POWER VOLUME POWER 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 19
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Radar Cross-section Comparison: Mag. Coord. of ROI centre 6.35⁰N, 150.90⁰E 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 21
Radar Cross-section Comparison: Mag. Coord. of ROI centre 6.35⁰N, 150.90⁰E 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 22
Radar Cross-section Comparison: Mag. Coord. of ROI centre 12.84⁰N, 149.98⁰E 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 23
Radar Cross-section Comparison: Mag. Coord. of ROI centre 12.84⁰N, 149.98⁰E 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 24
Conclusion: SAR can be helpful in augmenting and complementing GPS in scintillation studies Demerit: SAR image pair with unchanged background Need: simple identification techniques Coeff. of Variation of Intensity is not a good measure Introduction of Total Power and Depolarized Power measures Varying response of SAR RCS to scintillation may be explained by many factors 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 25
Thanks for your attention Acknowledgement: Prof. Charles Carrano, ISR, Boston College Data: JAXA s RA6 Project No. 3169 and RA4 Project No. 1396 Shradha Mohanty shradha_mohanty@iitb.ac.in 12/11/2017 AGU FALL MEETING 11-15 DECEMBER 2017 NEW ORLEANS 26