- The document describes techniques for estimating ionospheric effects from SAR data using the ISCE software tool. - ISCE has new capabilities for processing polarimetric and polarimetric interferometric SAR (Pol-InSAR) data to estimate parameters like Faraday rotation and total electron content (TEC). - The ionospheric module in ISCE uses the Faraday rotation method to model calibrated polarimetric SLCs and estimate Faraday rotation angles and TEC from the data.

1. Techniques and Tools for Es2ma2ng
Ionospheric Effects from Interferometric
and Polarimetric SAR Data
P. Rosen, M. Lavalle, X. Pi, S. Buckley, W. Szeliga, H. Zebker*, E. Gurrola
Jet Propulsion Laboratory, California Ins6tute of Technology, Pasadena, CA 91109, USA
*Stanford University, Stanford, CA 94305, USA

2. Outline
 The ISCE soIware tool
• Mo6va6ons and overview
• Focusing approach and InSAR processing
 New features of ISCE
• Polarimetric and Pol‐InSAR capabili6es
• Ionospheric module: Faraday rota6on
• Ionospheric module: Split Spectrum
 Conclusions and future developments
IEEE IGARSS 2011  Vancouver July 26, 2011 2

3. The ISCE soIware tool
ISCE
 Background
• Two NASA sponsored InSAR workshops at Stanford
(2008) and Scripps (2011)
 Mo6va6ons
• To respond to the demand for an efficient, flexible and
extensible SAR/InSAR processor InSAR
 Objec6ve: to build a new SAR processing environment Scien6fic
•
•
accurate in phase and geoloca6on
easy to use, flexible, extensible and efficient
Compu6ng
• well documented, supported, accessible to all users Environment
 Delivered to US scien6sts by 2011
Gurrola, E., Rosen, P., Sacco, G., Szeliga, W., Zebker, H., Simons, M., Sandwell, D., Shanker, P., Wortham, C., Chen, A., “Interferometric
Synthe6c Aperture Radar (InSAR) Scien6fic Compu6ng Environment,” presented at AGU Fall Mee6ng, San Francisco, December 2010.
IEEE IGARSS 2011  Vancouver July 26, 2011 3

4. Focusing approach and InSAR with ISCE
 Focusing in ISCE is performed by the STDPROC
(Stanford processor) package
 STDPROC
• is based on ROIPAC and SRTM/UAVSAR
processors
• applies mo6on compensa6on
• InSAR SLCs are co‐registered to a reference
circular orbital trajectory
• SLCs are produced into a common
geographical coordinate system from the start
• suitable for 6me‐series and persistent
scaierers !
• efficient and fast
 ALOS, RADARSAT, TERRASAR‐X, ERS, J‐ERS supported
Zebker, H.A.; Hensley, S.; Shanker, P.; Wortham, C.; , "Geode6cally Accurate InSAR Data Processor," Geoscience and
Remote Sensing, IEEE Transac6ons on , vol.48, no.12, pp.4309‐4321, Dec. 2010
IEEE IGARSS 2011  Vancouver July 26, 2011 4

5. InSAR processing with ISCE
Level 0 data Level 0 data
data extrac6on data extrac6on
 InSAR processing flow
• steps similar to ROIPAC flow
• SLC coregistra6on needed only at sub‐
mo6on compensa6on and pixel level
focusing to ref. trajectory
• takes advantage of the improved
focusing
• more accurate geocoding of
fine co‐registra6on and
resampling interferograms
• execu6on is fast and efficient
interferogram and • can be used with different polariza6on
DEM
correla6on es6ma6on
channels (useful for Pol‐InSAR technique)
topography removal
geocoding
post‐processing
IEEE IGARSS 2011  Vancouver July 26, 2011 5

6. Architecture of ISCE
Docs
Applica6ons (or modules)
Library necessary informa6on for
main python scripts that take user
support files for modules and installing, execu6ng and
inputs and manage the execu6on of
components extending the modules in ISCE
various components (e.g., insar.py)
ISCE Source Dir View
Contrib
gives the users the
opportunity to extend ISCE
with external contribu6ons
Packages and components
!
python and C/Fortran rou6nes
that execute single tasks in the
processing chain
IEEE IGARSS 2011  Vancouver July 26, 2011 6

7. New ionospheric module (ISSI)
NEW package in ISCE for ionospheric studies using SAR data (ISSI)
 Provides end‐to‐end processing from L0 data to geocoded products
 Generates absolute TEC maps and differen6al TEC maps
 U6lizes components from STDPROC (e.g. focusing)
 Embeds NEW modules: polarimetric SLCs, Faraday rota6on and
split‐ spectrum
ISCE Source Dir View
NEW package
NEW applica*on ISSI
Polarimetric SLCs
Ionosphere (ISSI)
Faraday rota6on
Split‐spectrum
!
IEEE IGARSS 2011  Vancouver July 26, 2011 7

8. Polarimetric SLCs in ISCE
Full‐pol SLCs in Pauli
basis geocoded with
 ISCE forms a set of calibrated polarimetric SLCs, i.e. the SRTM DEM
full‐pol 2×2 scaiering matrix
 5 calibra6on steps include
• polarimetric calibra6on
• range spreading loss correc6on
• antenna paiern correc6on
• incidence angle correc6on
• absolute radiometric calibra6on
 SLCs can be exported to community tools for polarimetric
post‐processing (e.g., ESA/PolSARPro, DLR/RAT)
 geocoded quad‐pol 4×4 covariance matrix (i.e., all
polarimetric products are readily geocoded)
 Several polarimetric products can be focused in the same
exact geometry (useful for polarimetric series analysis)
 Product quality assessment in progress
IEEE IGARSS 2011  Vancouver July 26, 2011 8

9. Polarimetric Interferograms in ISCE
volume‐dominated coherence
Pol‐InSAR coherence set
ground topography
 ISCE allows genera6ng polarimetric
interferograms
 Geocoded Pol‐InSAR 6×6 covariance matrix
 Pol‐InSAR matrix can be exported to third‐party
soIware tools for Pol‐InSAR post‐processing
 Useful for applica6ons in agriculture and forestry
M. Lavalle and M. Simard, Exploita6on of dual and full Pol‐InSAR data: from raw
data to geocoded products, ALOS PI Symposium 2010, Tokyo, Japan.
9
‐π π 0 1

10. Ionospheric module in ISCE:
Faraday rota6on method
 The polariza6on plane rotates while radar waves
travel through ionosphere
 Transmiied and incident waves differ
 Faraday rota6on > 5deg‐8deg affects applica6ons
of radar polarimetry
 Knowledge of Faraday rota6on angle Ω can be used
 to improve data quality of SLCs
 to map TEC in the ionosphere
magne6c field
K
Ω≅ B cos( )sec(θ 0 ) TEC
ψ
f2
frequency total electron
content
one‐way FR angle
IEEE IGARSS 2011  Vancouver July 26, 2011 10

11. Ionospheric module in ISCE:
Faraday rota6on method
 Polarimetric system model contains
 Distor6ons from radar instrument (channel imbalance and cross‐talk)
 Faraday rota6on
 The measured scaiering matrix M is corrected for channel imbalance and cross‐talk (i.e.,
polarimetric calibra6on) before es6ma6ng Faraday rota6on
Pi, X., Freeman, A., Chapman, B., Rosen, P., Li, Z., “Imaging ionospheric inhomogenei6es using spaceborne synthe6c
aperture radar,” J. Geophys. Res., in press, 2011.
IEEE IGARSS 2011  Vancouver July 26, 2011 11

12. Ionospheric module in ISCE:
Faraday rota6on method
L1.0 polarimetric data
mo6on compensa6on VH/VV azimuth
data extrac6on
and focusing resampling
 Model of calibrated polarimetric SLCs
data calibra6on
 M HH M HV   cos Ω sin Ω  S HH S HV  cos Ω sin Ω 
  = Ae jφ 
 − sin Ω cos Ω  S
  
M
 VH M VV 
   VH SVV  − sin Ω cos Ω 
 
calibrated
polarimetric SLCs
 Conversion to circular basis
 M LL M LR   1 j  M HH M HV  1 j  magne6c
 =    field data
M
 RL M RR   j 1  M VH
   M VV  j 1 
 
 FR and TEC
Faraday rota6on and
1 K
(
Ω = arg M LR M * ) Ω ≅ 2 B cos( )sec(θ 0 ) TEC
ψ TEC es6ma6on
4 RL
f
S. H. Bickel and R. H. T. Bates “Effects of magneto‐ionic propaga6on on the polariza6on
scaiering matrix,” Proc. IEEE (Short Papers), vol. 53, p.1089 , 1965.
IEEE IGARSS 2011  Vancouver July 26, 2011 geocoding 12

13. Results: FR/TEC map from ISCE
(SRTM‐geocoded)
calibrated
polarimetric SLCs
magne6c
field data
Faraday rota6on
angle map
Faraday rota6on and TEC
es6ma6on
geocoding
low‐SNR areas
15 deg  Faraday rota6on and TEC are related by
a constant scale factor
K
Ω≅ B cos( )sec(θ 0 ) TEC
ψ
f2
0 deg IEEE IGARSS 2011  Vancouver July 26, 2011 13

14. Ionospheric module in ISCE:
split‐spectrum technique
 InSAR phase contains non‐dispersive and dispersive contribu6ons
 Dispersive contribu6on depends on wavelength and differen6al TEC
 Split spectrum technique extracts the dispersive contribu6on from InSAR
phase and calculates the differen6al TEC
non‐dispersive dispersive
InSAR phase term term
4" B" 4" 4" 4" 4! K
!! = z+ $ rg + $ ratm + $ rion = # rnd + 4! 2 "!Te
# r' # # # " c
differen6al
TEC
4" 4" K K
!!ion = $ rion = !Te = 4" 2 #!Te
# # f2 c
Rosen, P.A., Hensley, S., Chen, C., "Measurement and mi6ga6on of the ionosphere in L‐band Interferometric SAR data," Radar
Conference, 2010 IEEE , pp.1459‐1463, 10‐14 May 2010.
IEEE IGARSS 2011  Vancouver July 26, 2011 14

15. Ionospheric module in ISCE:
split‐spectrum technique
 Es6ma6on approach
• signal spectrum split in two por6ons
• each por6on contains same non‐dispersive effects and different
dispersive effects
signal spectrum sub‐spectrum 1 sub‐spectrum 2
! !1 !2
 The differen6al TEC is calculated from the InSAR phase of the two por6ons
InSAR phase differen6al TEC
4" K "1
!!1 = $ rnd + 4" 2 #1!Te !!2 " !!1
#1 c "2
!Te =
4# K 2
2 ( 2
4" K " " "12 )
!!2 = $ rnd + 4" 2 #2 !Te "2 c
#2 c
IEEE IGARSS 2011  Vancouver July 26, 2011 15

16. Ionospheric module in ISCE:
split‐spectrum technique
L1.0 InSAR data
data extrac6on mo6on compensa6on
fine co‐registra6on
and focusing to reference
and resampling
data extrac6on trajectory
 The signal spectrum can be split aIer fine co‐registra6on and
resampling split spectrum
 The two SLCs pairs are used to generate two interferograms
 From two InSAR phases the differen6al TEC map is calculated
!1 !2
and geocoded lower‐ and
 Split‐spectrum technique successfully applied to PALSAR upper‐band SLCs
single‐pol data over Sichuan, China (Rosen et at., 2010)
interferogram es6ma6on
and unwrapping
differen6al TEC
geocoding
es6ma6on interferogram es6ma6on and
unwrapping

17. Split‐spectrum in ISCE
 Test using ALOS/PALSAR quad‐pol data (14 MHz bandwidth)
 Two acquisi6ons on April 1st, 2007 and on May 17th, 2007
 Strong gradient of FR visible only on April 1st data
PALSAR FR map PALSAR FR map
APRIL 1st, 2007 MAY 17th, 2007
15 deg 0 deg
0 deg ‐15 deg
IEEE IGARSS 2011  Vancouver July 26, 2011 17

18. Split‐spectrum in ISCE
PALSAR FR map interferogram
APRIL 1st, 2007 phase
 First analysis revealed a dense
fringe paiern associated with FR
gradient
 The paiern confirms the phase
delay caused by the ionosphere
 Coarser azimuth resolu6on
improves the paiern visibility
15 deg
 Full analysis and es6ma6on of
differen6al TEC in progress
0 deg
IEEE IGARSS 2011  Vancouver July 26, 2011 18

19. Conclusions & future developments
 ISCE is a new SAR processing environment developed within a JPL‐Stanford collabora6on
• designed for InSAR processing
• extended to polarimetric processing
• available to US scien6sts by 2011
 Unique features of ISCE
• modular, extendible, flexible, fast
• accurate geocoding of output products
 New ionospheric package recently added into ISCE
• Es6ma6on of Faraday rota6on and TEC maps
• Differen6al TEC maps generated from split‐spectrum technique
 Future developments
• Product quality assessment
• New high‐priority packages: 6me‐series, PS methods, Pol‐InSAR, GUI
• Integra6on with community tools (e.g., GMT, PolSARPro)
• Extension to cloud compu6ng
IEEE IGARSS 2011  Vancouver July 26, 2011 19