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1
PALSAR SCANSAR SCANSAR Interferometry
Masanobu Shimada
Japan Aerospace Exploration AgencyEarth Observation Research Center
ALOS PI symposium, GreeceNov. 6 2008
Introduction
•L-band PALSAR strip mode with 70km swath can effectively achieve the deformation mapping even for the vegetation covered area. (Chuetsu-oki, Noto, Solomon, Iwo, Hawaii, etc.)
•PALSAR SCANSAR with 350km swath is more effective than the repetitive observations of the STRIP mode for global land observation. SCANSAR SCANSAR interferometry (SSI) is also important tool for the earth observation.
•Azimuth signal spectrum is the dispersive and transmission beam synchronization is mandatory for the SSI.
•PLASAR activation timing is controlled by 1 sec as the normal operation. This has been limiting the SSI for long time.
•Here, we conducted the experiomental activation of the PALSAR for SSI performance evaluation. The target area was Africa (Sahara desert and Tanzania) and Amazon.
•We introduce the results of the first PALSAR SSI.
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PALSARL-band (23.6 cm)Synthetic Aperture RadarPolarimetryDual PolarizationSCANSAR
The Advanced Land Observation Satellite - ALOS
Launch:24 Jan. 2006
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PALSAR SCANSAR
WB1 : Bw 14 MHz, 5 SCANs, 3looks ~ 7 looks, 120 Mbps
WB2 : Bw28MHz, 5 SCANs, 1~ 3 looks, 240 MHz
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Timing block diagram (1)
timing
area
Final image
prffDD
⋅ vg
nn:pulses
prffDD ⋅ nn
⋅ vg
spacing
Ts
Timing allocation block diagram
timingnn:pulsesTs
S/C
Frequency (master)
BW = − fDD ⋅rg ⋅ βvg
BSw = − fDD ⋅Ts ⋅Nlook
ρ = BW
BSW⋅L2≅ 5 ⋅ L
2
Azimuth Bandwidth
AB for swath I
resolution
Power spectrum of the SCANSAR in azimuth (spectrum diversity).
SSI condition
2D spectrum (range and azimuth) should be the same.
Assumption10 % allowance for azimuth spectrum
ΔTs < 0.1Ts ~ 0.014 s. ~ 90mWhere, 1st scan, Ts~0.2 sCorresponding position allowance is 90m
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Expression for the ground target point (rp)
fd =fPRF
nni (− nn
2≤ i < nn
2)
fd =2λ
vs − vp( )⋅ rp − rs
rp − rs
z = F rp( )xp
2
Ra2 +
yp2
Ra2 +
zp2
Rb2 =1 (if z = 0)
fd: Doppler frequency vs:satellite velocityfPRF:Pulse repetition frequency vp:target point velocitynn:burst numbers i: azimuth addressrp:position vector of the pixelrs:position vector of the satellitez:height of the targetF(): function giving the height
InSAR processing Routine(SPECAN)
Master Slave
Telemetry: Doppler Model
Telemetry: Doppler Model
Range compression
SPECAN (Azimuth)
Co-registration
summing(box car)n-look processing Bp correction
Terrain correction
common
Curvature
Range compression
SPECAN (Azimuth)
Curvature
output
fD = a0 + a1 ⋅ r + a2 ⋅ r2Doppler model :
γe jϕ =a ⋅b*
a ⋅ a* ⋅ b ⋅b*
rg' = a + b ⋅ rg + c ⋅az
az' = d + e ⋅ rg + f ⋅az
master slave coherence fringe
Sample result of the InSAR products output from the Browse InSAR processor (SPECAN) : Functionality test
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Results of Browse-InSAR(2006/8/2-2006/5/2)(Specan processing@SIGMA-SAR)
Coherence DEM Deformation Amplitude
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Results from FBS DinSAR: 2006/8/2-2006/5/2:Bp=80m(Correlation processing@SIGMA-SAR)
Coherence DTM Deformation Amplitude
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prf11
prf12
prf21
prf22
prf31
prf32
prf41 prf51
prf42prf52
1 2 3 4 5
time
T1 1) Normal operation•T1 is 1s unit. (Even same latitude is set for the first transmission, 7km dislocates at maximum)•prf is tabulated every 100 m height.
-> SSI could be done by chance( But, never realized the SSI)
2) Special operation•Specify the followings
Latitude of argumentFive prfs
[Note:Latitude of augment from GPS is biased(0.993km).]-> SSI can be done.
Operational constraints and achievement for PALSAR SSI
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SCANSAR SCANSAR InSAR experimentsDuration April 2 - April 17 2008Sites: Sahara, Tanzania, AmazonMode WB1 and WB2
50%
80%
BS
168m
228m
Bp
Differs in prfNGWB22/234/9
Large BpNGWB22/284/14OKWB13/24/17
Differs in prfNGWB12/294/15NGWB12/284/14NGWB12/274/13
Different locationDifferent location
Area
NGWB12/194/5
OK
NG
Result
WB12/244/10
WB12/164/2
ModeSlaveMaster
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SCANSAR parameters : Beam synchronization
500m0.5168m20080302200804172800m0.8228m20080224200804101LoΔpBpSlaveMasterCase
5.380.791Total1.160.1711915.732751.150.1642159.835541.090.1601715.227431.020.1502369.735620.9930.1461692.02471Length (km)Duration(s)PRFPulsesNo
Δp j =Lo j
L j
LO
L
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Location of the test paths
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350km
Amplitude
April 10 - Feb. 24Bp=~200mBeamS~80%Tanzania
19Coherence
20Flat earth corrected fringe
21Deformation (cancelled for the low frequency)
22
RSP325Sahara
2008/4/17-2008/3/2
Bp=~100m
BeamS~50%Coherence Amplitude
DTM Deformation
23
WB1
WB2
May 16 2006-Oct. 22 2007
SC
AN
SA
R data archives
Conclusions
PALSAR SCANSAR SCANSAR Interferometry has been examined and succeeded by conducting the beam synchronization with the previous images.
The parameters are the PRFs and augment of latitude for the first scan.
Two examples out of 9 examples show that 80% and even 50% of the beam synchronization can produce the SSI over the dense forest and desert of Africa.
It promises that PALSAR can provide the SCANSAR SCANSAR Interferometry for wide range of the target, i.e., earthquake, Antarctica, Greenland monitoring.
Further researchCorrection of the SCAN-SCAN phase offsetCorrection of the atmospheric error and orbital errors.Improvement of the processing speedTrial for Full aperture type processing