SMOS:
Principles of Operation
of the MIRAS instrument
Prof. A. Camps
Dept. de Teoria del Senyal i Comunicacions
Universitat Politècnica de Catalunya and IEEC/CRAE-UPC
E-mail: camps@tsc.upc.edu
…on behalf of many people (many anonymous)
that kept this dream alive and make it happen
devoted to Prof. Cal Swift… the pioneer
SMOS: Principles of Operation & First Results
ICMARS 2010
Jodhpur – India December 16th, 2010
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Outline of the presentation:
1.
2.
Basic principles
Imaging in Synthetic Aperture Radiometers:
2.1. Synthetic Aperture Radiometers
2.2. Image Reconstruction Algorithms: Ideal Case
3.
4.
The SMOS Mission
MIRAS instrument description
4.1. Array topology
4.2. Receivers’ architecture
4.3. NIR architecture
4.4. DIgital COrrelator System (DICOS)
4.5. CAlibration System (CAS)
5. Instrument Performance
5.1. Angular Resolution
5.2. Radiometric Performance: definition of terms
5.3. Image Formation Through a Fourier Synthesis Process
5.4. Imaging Modes: Dual-polarization and full-polarimetric
6. Geolocalization: from director cosines grid to Earth reference frame grid
and Retrieval of Geophysical Parameters
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ICMARS 2010
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1. Basic Principles
• Spatial resolution is achieved by cross-correlating the signals collected by a
number of antennas
• Antennas can have a wide beam or a narrow one in one or two directions
Channel 1
H1(f)
b1(t)
1
b1b2*
2
H2(f)
Channel 2
Baseline
Complex
Correlator
V u,v  =
T ( , ) 
b2(t)
1
kB B1B2 G1G2
1
*
b 1 t  b2 t 
2
Fn 1  ,  F *n 2  , TB  ,  Tph rec
1 2
1   2  2
,   sin cos, sin sin 
(u ,v )  (x , y ) 0 = antenna spacing normalized to the wavelength
Ideal case: - Identical antenna patterns
- Negligible spatial decorrelation
- No antenna positioning errors
SMOS: Principles of Operation & First Results
ICMARS 2010
Jodhpur – India December 16th, 2010
2D Fourier Transform
V (u,v )  F T (, )
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2. Imaging in Synthetic
Aperture Radiometers
2.1. Synthetic Aperture Radiometers using Fourier Synthesis:
Radioastronomy
VLA, New Mexico, Socorro
Earth Observation
(concept proposed in 1983 by LeVine & Good)
ESTAR
(1 D Aperture Synthesis)
 NASA
MIRAS
(2 D Aperture Synthesis)
 ESA
V (u,v )  F T (, )
SMOS: Principles of Operation & First Results
ICMARS 2010
Jodhpur – India December 16th, 2010
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• Differences between radio-astronomy and Earth observation:
- Large antenna spacing
- Very narrow field of view (FOV)
- Obliquity factor (1/cos ) can be approximated by 1
- Antenna patterns are approximatedly constant (amplitude and phase)
over the FOV
- Typically quasi-point sources imaged over cold background
 super-resolution image reconstruction algorithms can be used
SMOS: Principles of Operation & First Results
ICMARS 2010
Jodhpur – India December 16th, 2010
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. After the successful results of ESTAR radiometer (1988),
SSS image derived from the ’“Electronically Steered Thinned Array Radiometer (ESTAR)”.
Error = 0.3 psu (D. M. LeVine et al., NASA Goddard).
the European Space Agency starts in 1993 the first feasibility studies to apply
synthetic aperture microwave radiometry in two dimensions:
. MIRAS concept is born: Microwave Imaging Radiometer by Aperture Synthesis
. First studies (1993-95): led by Matra Marconi Space as the prime contractor
. 1995 Soil Moisture and Ocean Salinity Workshop (ESTEC, the Netherlands)
Aperture Synthesis Microwave Radiometry is the only technique capable of measuring soil
moisture and ocean salinity with enough accuracy and spatial resolution.
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2.2. Image Reconstruction Algorithms: Ideal Case
Antenna Positions Spatial frequencies (u,v)
Periodic extension
u
v
V (u,v )  F T (, )
Fn  ,  TB  ,   Tph rec
2
T ( , ) 

Overlapping
of 1 alias
Overlapping
of 2 aliases
Alias-free
Field Of View
(AF-FOV)
1  2  2
21 elements + 2 redundant elements/arm
Antenna spacing d = 0.875 
Hexagonal grid in (u,v) plane
Nyquist criterion: d<  / 3
SMOS: Principles of Operation & First Results
ICMARS 2010
Jodhpur – India December 16th, 2010
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In SMOS the “alias-free FOV” can be enlarged since part of the alias images
are the “cold” sky (including the galaxy!)  TB image limited by Earth replicas
Iso-incidence
angle contours
hsat=755.6 Km, =32.00º, d= 0.89 
hsat=755.9 Km, tilt=32.50, d= 0.88
2
2.80
101.26
1200
1.5
2.26
81.39
1000
1
1.84
65.47
800
Along track coordinate(Km)

0.5
0
-0.5
-1
1.50
53.04
600
400
1.39
51.36
1.25
44.31
-1.5
2.47
88.01
2.21
78.62
2.31
81.55
2.13
74.95
1.76
61.13
1.72
50 58.77
1.40
40 46.29
1.43
48.48
1.19
30
37.53
1.20
39.69
20
1.34
48.11
1.39
48.00
200
-2
1 -3
-2
-1
0
1
2
3
0

0.8
0.4
Boresight Distance: 912.65 Km
0.2
Boresight Incidence Angle: 36.35º
0
0.1
0.2
Extension of
Alias-Free FOV
0.3
0.4
1.13
40.12
1.27
40.33
1.10
32.62
10
1.05
34.97
1.20
32.85
1.23
35.52
1.39
35.77
0.6
0
60
0.5
0.6
1.49
39.34
-200
-800
0.7
0.8
0.9
-600
-400
-200
0
200
Cross track coordinate (Km)
400
600
800
1
- Pixel axial ratio a/b
- Spatial resolution defined as geometric
mean of axes
5.12
90.57
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3. The SMOS Mission
SMOS is a challenge:
Particularities of 2D aperture synthesis radiometers:
1) New type of instrument:
- Review of the fundamental equation
- Detail error model & error correction (calibration) algorithms
- Image reconstruction algorithms
2) New type of observations:
- Multi-look and multi-angle observations:
. different pixel size and orientation
. different noise and precision for each pixel
- Polarization mixing:
. Earth reference frame  antenna reference frame
3) New L-band and multiangular ocean
and soil emission models :
- Wide range of incidence angles (0º-60º)
4) New geophysical parameter retrieval algorithms
taking into account issues 1, 2 and 3 above
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ICMARS 2010
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SMOS Mission:
SMOS
Scientific measurements require a
- Sun-synchronous,
- dawn/dusk, and
- quasi circular orbit.
Proba-2
Orbital parameters:
• Mean altitude =
755.5 km
• Eccentricity =
0.001165
• Mean inclination =
98.416º
• Local Time Asc. Node =6 AM
• Argument of Perigee = 90º
• Mean Anomaly =
306.3º
Transformed
SS-19 missile
Note: The SUN is nearly always visible (97 % of the time) !!!
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ICMARS 2010
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4. MIRAS instrument
description
4.1. Array topology
Optical Splitter
LCF_A_21
ARM A
LCF_A_16
LCF_A_15
PD
LCF_A_10
LCF_A_09
CMN
• 69 antenna elements (LICEF)
• Equally distributed over the 3 arms and hub
• The acquired signal is transmitted to a central
correlator unit, which computes the complex crosscorrelations of all signal pairs.
Optical Splitter
LCF_A_04
LICEF
LCF_A_03
NS (DISTRIBUTED)
LCF_AB_01
LCF_A_02
LCF_A_01
PD
HUB
In the arms
In the Hub
3x3x6
3x4
66
-
3x1
3
CMN
3x3x1
3x1
12
CCU
-
1
1
3x3x1
-
9
Unit
LICEF
ST
CMN
1 SEGMENT
OF ARM B
PD
Optical Splitter
ST
LICEF/NIR
1 SEGMENT
OF ARM A
LICEF/NIR
NS (distributed)
CMN
LICEF/NIR
NS (centralised)
HUB
NS (CENTRALISED)
ARM B
ARM C
Optical
Splitter
CMN
ST
1 SEGMENT
OF ARM C
LICEF
Total
NIR_AB_02
-
1
1
PD (2 to 8)
3x3x1
3x1
12
Optical Splitter (1 to 8)
3x3x1
3x1
12
Optical Splitter (2 to 12)
-
1
1
TRANSMITTERS
-
2
2
FILTERS
-
2
2
X-ANTENNA
-
1
1
LICEF/NIR
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ICMARS 2010
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MIRAS consists of a central structure (hub) with 15 elements, and 3 deployable arms,
each one having 3 segments with 6 antennas each.
SMOS: Principles of Operation & First Results
ICMARS 2010
Jodhpur – India December 16th, 2010
[credits EADS-CASA]
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CAL  A  e j  UNCAL  Offset
4.2. Receivers’ architecture:
SLOPE
IF
ATTEN
CORR.
FILTER
1404-1423 MHz
ANTENNA SWITCH ISOL LNA
BPF RFAMP
1BIT
ADC
IF AMPs
I
DI
MIXER
TI
H
V
C
U
DICOS
8-27 MHz
TQ
TRF
Q
DQ
SYNTH
MAIN PATH GAIN = 100 dB
PMS PATH GAIN = 65 dB
REF
55.84 MHz
1396 MHz
DICOS
VCO
SLOPE
IF
ATTEN
CORR.
FILTER
1BIT
ADC
IF AMPs
PMS
• PMS acts as a total Power Radiometer in each LICEF
TA  aVout  b
• Needed to denormalize the “normalized” correlations (1 bit/2 level)
SMOS: Principles of Operation & First Results
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LICEF: the LIght and Cost Effective Front-end
[credits MIER Comunicaciones]
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4.3. NIR architecture
The Noise Injection Radiometer (NIR) is fully polarimetric and operates at 1.4 GHz
3 NIRs in the hub for redundancy.
Functions:
• precise measurement of Vpq(0,0) = TApq for mean value of TBpq(,) image.
• measurement of noise temperature level of the reference noise source of Calibration
Subsystem (CAS)  absolute amplitude reference
1st LICEF unit
(V-pol)
Correlated noise inputs
(from Noise Distribution Network)
allow phase/amplitude calibration of
receivers as LICEFs & for 3rd and 4th
Stokes parameters measurements
Controller unit
(switches, noise injection...)
2nd LICEF unit
(H-pol)
[credits TKK]
SMOS: Principles of Operation & First Results
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SMOS NIR:
[Colliander et al., 2005]
Normal mode of operation:
Calibrating internal noise source mode:
known
(cold sky)
T NA  + TA = TU
SMOS: Principles of Operation & First Results
?
T NA + TA = TREF + TNR 
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[credits HUT]
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4.4. DIgital COrrelator System (DICOS)
1 bit ADC (comparator)
in each LICEF
Correlator =
= NOT-XOR + up-counter
Digital signals from each LICEF are transmitted to DICOS to compute
the complex cross-correlations of all signal pairs.
SMOS: Principles of Operation & First Results
ICMARS 2010
Jodhpur – India December 16th, 2010
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• Lower half: II-correlations: Nr,Nc  Zr  r  Vr
• Upper half: IQ-correlations: Ni,Nc  Zi  i  Vi
• Diagonal:
IQ-correlations of same
element (q: quadrature errors)
• Correlations of I and Q signals with 0’s and 1’s
to compensate comparators’ threshold errors
• Correlations of 0’s and 0’s and 1’s and 1’s = Ncmax
• NCmax = 65437 for dual-pol mode (= fCLK ·  int)
NCmax = 43625 for full-pol mode
•Total number of products:
•2556 correlations Ik-Ij
•2556 correlations Ik-Qj
•72 correlations Ik-Qk
•72 correlations I-0
•72 correlations Q-0
•72 correlations I-1
•48 correlations Q-1
•36 control correlations between 1 and 0 channels (4 for each ASIC)
SMOS: Principles of Operation & First Results
ICMARS 2010
Jodhpur – India December 16th, 2010
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CCU: the Correlator and Control Unit
[credits EADS-CASA]
SMOS: Principles of Operation & First Results
ICMARS 2010
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4.5. CAlibration System (CAS)
Noise sources needed to calibrate the instrument.
HUB
SMOS: Principles of Operation & First Results
ARMS
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Centralized and distributed calibration
Correlated noise is injected to the receivers in two steps:
first the “even” sources and then using the “odd” ones
48
Overlapping between elements
(phase & amplitude tracking
along the arms)
* source 0
* source 2
* source 5
* source 8
B
Centralized Calibration
(separable & non-separable
errors can be corrected)
Distributed Calibration
(only separable errors
can be corrected)
49
A
24
1
25
C
These receivers belong to
the NIR (□: H-channel) and
do not form additional baselines
Overlapping between elements
(phase & amplitude tracking
among arms)
72
SMOS: Principles of Operation & First Results
ICMARS 2010
Jodhpur – India December 16th, 2010
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OVERALL SEGMENT ARCHITECTURE
SMOS: Principles of Operation & First Results
ICMARS 2010
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[credits EADS-CASA]
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6 LICEF / segment
SMOS: Principles of Operation & First Results
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[credits EADS-CASA]
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MOHA
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[credits EADS-CASA]
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CAS
SMOS: Principles of Operation & First Results
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[credits EADS-CASA]
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CMN
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[credits EADS-CASA]
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5. Instrument Performance
5.1. Angular Resolution
V (u, v ) =
1
12

 T  ,   T

B
ph rec
F
n1
( , )Fn*2 ( , )
1  2  2
 2  2 1
 u  v  -j 2  u +v 
d d
r n12  
e
f0


• The “ideal” brightness temperature image is formed by an inverse
(discrete) Fourier transform of the measured visibility samples (B = 0):

1
j 2 u   v 
Tˆ  ,   s  W  umn , v mn  V 0 umn ,v mn  e  mn mn    T  ' , '
K
m n
 ' 2  ' 2 1

AF 0    ',   '  d ' d '
Equivalent Array Factor:
same response as for an array of elements at (u,v) positions
(except for the |(.)|2)
j 2  umn   '  v mn   '  
3 2
s 
d
2
AF 0    ',   '   s  W umn , v mn  e
m
n
• The retrieved Τ̂  ,  image is the 2D convolution of the original T(,) image
with the instrument’s impulse response or equivalent array factor:
Τ̂  ,  = FH1  W u,v  V 0 u, v   = AF 0  ,  * Τ  ,  
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Response with
rectangular window
 rect
3 dB 
 2
umax
; e  10% for umax  15
umax  2 3NEL d
MBE  43%
Response with
Blackmann window
(rotational symmetry)
 Blackmann
 1.48 rect
3 dB
3 dB
MBE  90%
TA'  MBE  Tmain lobe  1  MBE   Tsec ondary lobes
SMOS: Principles of Operation & First Results
ICMARS 2010
Jodhpur – India December 16th, 2010
W(umn,vmn): window
to weight the visibility
samples:
• reduces side lobes
• widens main lobe
• increases main beam
efficiency (MBE)
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5.2. Radiometric Performance: definition of terms
Error maps: TB(,,t)
Random errors
(noise due to finite
integration time)
Systematic errors
(instrumental errors)
Temporal average
Zero
Temporal standard
deviation
Radiometric
sensitivity
Spatial average
Radiometric bias
(scene bias)
Spatial standard
deviation
Radiometric accuracy
(pixel bias)
SMOS: Principles of Operation & First Results
ICMARS 2010
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0
M
Tsensitivit y 
Tbias 
 T̂ , , t   T̂ , , t  
 B


i
B
t
i1 
M 1
2
1 N 

 T̂B i , i , t   TB i , i 

N i1 
t

N
Taccuracy 
 
i 1
T̂B  i , i , t 
2
t
 TB  i , i  

N 1
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Radiometric Sensitivity over ocean
Dashed lines. Theoretical formula:
TB ( , ) 
3 2 TA  TR  a
d
1   2  2 w N
2
B eff t ( , )
Cut for =0
[credits I. Corbella]
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Galaxy
Alias
Moon
Cosmic Background Radiation at
3.3 K
Scene Bias < 0.1 K
Accuracy < 0.5 K
Sun
Alias
Galaxy
(yellowish)
Galactic radiosource (TBC)
[credits DEIMOS]
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Incidence angle dependence
Singularity in the transformation
antenna to Earth reference frame
(dual-pol mode)
• 45 deg singularity
discarded
• All points with the
same incidence angle
averaged
TX  cos 2  sin 2   TH 

T    2
2 
 Y   sin  cos   TV 
Fresnel
[credits I. Corbella]
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5.3. Image Formation Through a Fourier Synthesis Process
Even in the ideal case:
- Antenna spacing > /3  aliasing
- Gibbs phenomenon near the sharp transitions (mainly alias borders)
In the real case:
- Antenna patterns are different
- Receivers’ frequency responses are different (  FWF different)
- Antenna positioning errors  (u,v,w)real different from (u,v,0)ideal
IHFFT cannot be used as image reconstruction method
More sophisticated algorithms must be devised
But it will be good that the second ones tend to IHFFT in ideal
conditions
… and obviously instrumental errors must be calibrated first!
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Real Aperture Radiometer:
1 step calibration
TB imaging pixel by pixel
through antenna scan:
1)
Aperture Synthesis Radiometer:
2 step calibration
TB imaging in a single snap-shot
(1 integration time = 1.2 s / polarization in dual-pol):
1) Receivers relative calibration (image “contrast”)
- Error model (distorsions, artifacts, blurring…)
- Internal references (Tcorr, Tuncorr,…)
Absolute calibration
External references:
Thot, Tcold
*** Imaging by (e.g.) conical scan ***
*** Image Reconstruction Algorithm ***
2) Absolute Calibration (image accuracy)
- External references (FTT, OTT…)
- Thot/Tcold, ground truth, external calibration…
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Calibration Concept: Brief sketch
•
•
Items that need calibration:
-
NIR Gain and Offset
-
PMS gain and offset (receiver and baseline amplitude errors)
-
Fringe-washing function FWF (amplitude and phase errors)
-
Noise that is injected to receivers during calibration
-
Correlator Offsets
Types of Calibration:
– Internal: injection of correlated or uncorrelated noise to the receivers
–
External: observation of known target:
• NIR absolute calibration
• Flat-Target Transformation: to calibrate antenna pattern errors
–
CAS Calibration: performed by NIR during internal calibration
–
Correlator Calibration: injecting known signals
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a. MIRAS internal calibration
Instrumental errors correction: set of
measurements and mathematical
relations to remove instrumental
errors
INTERNAL
INSTRUMENT
CALIBRATION
Error model
• Characterizes the instrument behavior independently of the input signal.
• It can be characterized by suitable internal known signals injected at its
input: correlated/uncorrelated and hot/cold noise injection.
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MIRAS Internal calibration
PMS gain PMS offset
LICEF
PMS
Matched load
Hot
Mixer
i
ADC
IF-i
H
CC
vk  GkTsys
 voffk
k
To correlator matrix
Antenna
switch
U
v
L
RF
V
C
q
ADC
IF-q
TS1
TS2
Noise
distribution
network
0
N
LO
distribution
C
Reference receiver
(Noise Injection
Radiometer)
H
Noise
source
V
NIR
Warm
(*)
Clock
distribution
Tˆkj  Sk 0 S *j 0TS  Sk 0 S *j 0Tn
CC
sysk
T
 T T
C
Nk
C
Rk
2
TN k  S k 0 TS  Tn (1  S k 0 )
2
SMOS: Principles of Operation & First Results
(*)
Tˆkj Gkj
M 
C
kj
Correlation
amplitude
CC CC
Tsys
T
k sys j
Calibrated visibility:
TN
Vˆkj 
AC
sysk
T
ICMARS 2010
Jodhpur – India December 16th, 2010
1
*
SCAk SCA
j

M kjA TsysACk TsysACj
Gkj
vk  voffk
Gk
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Formulation of the Problem:
Instrument Equation After Internal Calibration
pq
12
V
1
12




  1
2
2
Tpq  ,   Trec pq
1  2 2
Fnp1  ,  F
*
np 2
fore
exp  j 2 u12  v12  w12 1   2   2
2
 u  v  w
2
12
12
12 1  
 ,  r12  
f0

 d d
Phase of fringe-washing function
Amplitude of fringe-washing functions
8
1.05
To be corrected using
the Flat Target Response
1
4
0.9
pp
ij
2
0.85
Deg
pp
ij
6
0.95
V (u,v )  V (u,v )  V (u,v )
pp
ij




0
0.8
0.75
W u, v  V u,v   G  T dec  ,  
-2
0.7
-4
0.65
0.6
-30
-20
-10
0
time (ns)
10
20
30
-6
-30
-20
-10
0
time (ns)
10
20
[credits I. Corbella]
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30
The Flat Target Response:
-The Flat Target Response is defined by:
Vij ,pq (u,v;1) 
1
i  j

Fn,i,p ( , )Fn, j,q * ( , )
  2 1
2
 u  v   j 2 (u v )
rij  
d d
e
2
2
fo 
1   

1
Vijpq (u,v;To  Tr )  To  Tr  Vij ,pq (u,v; 1)
defining:
TBpp  Tr pp
V (u,v ) 
Vij (u,v ; TP  Tr)
TP  Tr
pp
ij
Then the differential visibilities to be processed are:
Vijpp (u,v )  Vijpp (u,v )  Vijpp (u,v )
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External calibration
• Once in a month (every week during commissioning) the platform rotates
to point to the cold sky
• External calibration is used to correct for elements not included in
internal calibration: switch and antenna losses
• Also the Noise Injection Radiometer (NIR) is calibrated and the Flat
Target Response (FTR) measured
HERE IT GOES THE ANIMATION.
T_X_skylook2.gif
HERE IT GOES THE ANIMATION.
T_Y_skylook2.gif
Tx and Ty while satellite is turning up
SMOS: Principles of Operation & First Results
ICMARS 2010
Jodhpur – India December 16th, 2010
[credits I. Corbella]
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5.4. Imaging Modes: Dual-polarization and full-polarimetric
Dual-polarization radiometer:
MIRAS has dual-pol antennas, but only one receiver
 polarizations have to be measured sequentially,
with an integration time of 1.2 s each
[credits M. Martin-Neira]
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Jodhpur – India December 16th, 2010
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Full-polarimetric mode: (selected as operational mode for SMOS)
[credits M. Martin-Neira]
SMOS: Principles of Operation & First Results
ICMARS 2010
Jodhpur – India December 16th, 2010
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6. Geolocalization and Retrieval
of Geophysical Parameters
6. Geolocalization: from director cosines grid to Earth reference frame grid
• ISEA family of grids seem to be the best option for the SMOS Products, but EASE-Grid has
come to be popular amongst many of the Earth Observation missions of the USA, namely AQUA
(NASA/NASDA) and AQUARIUS (NASA), which are particularly interesting for comparison with the SMOS
products.
• Spatial partitioning of EASE-Grid is square-based and ISEA can be triangular,
hexagonal or diamond-based:
- In its hexagonal form, ISEA has a higher degree of compactness, quantize the plane with the smallest
average error and provides the greatest angular resolution.
-ISEA hexagonal possesses uniform adjacency with its neighbors, unlike the square EASE-Grid.
• Both grids have uniform alignment and are based on a spherical Earth assumption.
• ISEA hexagonal at aperture 4 and resolution 9 (15km) is made up of 2,621,442 points
and the EASE-Grid at 12km has 3,244,518 points.
• EASE-Grid is congruent, whereas ISEA is not congruent, being impossible to decompose
a hexagon into smaller hexagons or aggregate hexagons into larger ones. This would be a
negative feature for real-time re-gridding, but in SMOS the grids will be pre-generated.
SMOS: Principles of Operation & First Results
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Auxiliary data
Snap-shot 1
OS map
(1 overpass)
Spatio-temporal
averaging
Snap-shot 2
Snap-shot 3
Multi-angular
emission models
SM map
(1 overpass)
Snap-shot 4
L1 processor
L2 processor
L3 processor
• Atmospheric and foreign sources corrections
• Use of multiangular information:
1. Th & Tv or Tx and Ty + Faraday and geometric rotations corrections:
Earth  Antenna: retrieval in antenna ref frame,
Antenna  Earth: retrieval in Earth ref frame,
2. First Stokes parameter: I = Tx+Ty=Th+Tv. (invariant to rotations)
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• Sample SMOS data: Pixel in different positions of SMOS swath
(pin 3)
(pin 5)
SMOS: Principles of Operation & First Results
ICMARS 2010
Jodhpur – India December 16th, 2010
OS retrieval:
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• Sample SMOS data over Australia: Murrumbidge catchement
40 km SMOS soil moisture [m3/m3]
60
km
1 km downscaled SMOS soil moisture [m3/m3] using MODIS VIS/IR data
(a) Murrumbidgee catchment
(b) MODIS NDVI [m3/m3]
(c) MODIS LST [m3/m3]
(a) 60 x 60 km Yanco
site
in
the
Murrumbidgee
catchment,
SouthEastern Australia, (b)
1 km MODIS NDVI,
and (c) and LST [K]
on January 19, 2010.
SMOS: Principles of Operation & First Results
Sample results of the application of the downscaling algorithm to a
SMOS image covering the Murrumbidgee catchment, South-Eastern
Australia, on January 19, 2010 (6 am). First row: 40 km SMOS soil
moisture [m3/m3] over Murrumbidgee (left), and zoom into Yanco site
(right). Second row: 1 km downscaled soil moisture [m3/m3] over
Murrumbidgee (left), and zoom into Yanco site (right). Dots indicate
the location of the soil moisture permanent stations within the
Murrumbidgee catchment used for validation purposes with colors
representing their measurement at the exact SMOS acquisition time
(only within Yanco site). Empty areas in the images correspond to
non-retrieved soil moisture or clouds masking MODIS Ts
measurements.
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Thanks for your attention!
SMOS: Principles of Operation & First Results
ICMARS 2010
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