AMSR2 characterization and calibration

X-cal Working Group Meeting

University of Central Florida/Orlando

1 1

AMSR2 characterization and

calibration

Marehito KASAHARA

Japan Aerospace Exploration Agency

GCOM Project Team

21 February 2013

Overview of GCOM-W1

2

GCOM-W1

Orbit Sun synchronous

sub-recurrent orbit

Recurrence cycle 16 days

Altitude 700 km

Inclination 98.2 deg

Local sun time of

descending node

1:30

mass <1,991kg

power > 3,880W

Design life 5 years

AMSR2

Control Unit

(CU)

AMSR2

Sensor Unit

(SU)

GCOM-W1 orbit Identical to that of Aqua

Joining Afternoon constellation

Located in front of Aqua

(AMSR-E)

(AMSR2)

Overview of AMSR2

• AMSR2 Characteristics

3

Center

frequency

[GHz]

NEDT

[K]

Beam width

[degree]

(Ground resolution

[km])

6.925 / 7.3 < 0.34/0.43 1.8(35 x 62)

10.65 < 0.70 1.2(24 x 42)

18.7 < 0.70 0.65(14 x 22)

23.8 < 0.60 0.75(15 x 26)

36.5 < 0.70 0.35(7 x 12)

89.0 A/B < 1.20/1.40 0.15(3 x 5)

Rotation(40 rpm)

Off-nadir angle47.5 degrees

Altitude700 km

Incident angle55 degrees

Rotation(40 rpm)

Off-nadir angle47.5 degrees

Altitude700 km

Incident angle55 degrees

Scan type Conical scan

Swath width >1450 km

Antenna Offset parabolic antenna

with deployment mechanism

2-meter-diameter aperture

Incidence angle 55 degree

Dynamic range 2.7K-340K

Scan Geometry

Overview of AMSR2

4

Launch Lock

for SU

Stowed Deployed

Launch Lock for

Main Reflector

Feed-horn Array

Main Reflector

Orbital Balancing

Mechanism (OBM)

Stationary

part

Rotating

part

Cold Sky Mirror

(CSM)

calibration target

Feed-horn

Array

High-Temperature

Noise Source

(HTS)

• AMSR2 Sensor Unit Configuration

Overview of AMSR2

• Field of View (FOV)

FOV of CSM

(Fixed)

FOV of Main Reflector

(Rotating)

Cold Calibration

Target

(Cold Space)

Earth Observation

Target

5

In-orbit performance

GCOM-W1 Attitude Stability

6

Roll < ±0.002°

Pitch < ±0.003°

Yaw < ±0.005°


7

SU rotation stability Peak to peak variation is approximately 0.04 rpm (3LSB).

Fluctuation of Rotation Rate monitored every 1.5 sec.

39.96

39.97

39.98

39.99

40

40.01

40.02

40.03

40.04

0:57 1:12 1:26 1:40 1:55 2:09 2:24 2:38

Ro

tata

ion

rat

e [

rpm

]


Receiver Gain/Offset Control Automatic Gain Control (AGC) function works well.

8

-2100

-1400

-700

0

700

1400

2100

0

50

100

150

200

250

300

2:34:05 3:02:53 3:31:41 4:00:29

CSM

/HTS

co

un

t

Gai

n /

off

set

com

man

d c

ou

nt

89GA OFFSET(V) 89GA GAIN(V)

89GA(V) CSM count 89GA(V) HTS count

CSM nominal count range HTS nominal count range

Offset

Gain

HTS Count

CSM Count

Variation of AGC Command

9

HTS Thermal Stability (1/2) Variation of average temperature is within 0.6℃ over one orbit.

Temperature difference among 10 measurements is less than 0.6℃.


10

Image of thermal gradient 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

17

17.2

17.4

17.6

17.8

18

18.2

18.4

18.6

18.8

19

0:57 1:12 1:26 1:40 1:55 2:09 2:24 2:38

Max

. dif

fere

nce

［℃］

Pt-

sen

sor[℃］

2013/01/27 191D-191A

HTS TMP 1

HTS TMP 2

HTS TMP 3

HTS TMP 4

HTS TMP 5

HTS TMP 6

HTS TMP 7

HTS TMP 8

HTS TMP 9

HTS TMP 10

Average

Difference

Max-Min

290

295

300

305

310

0 500 1000 1500 2000 2500 3000 3500 4000

Tem

pe

ratu

re [

K]

Scan Number (3956 scans per orbit)

AMSR-E (8 points)

AMSR2 (10 points)


HTS Thermal Stability (2/2)

Considerable improvements was achieved from the

previous instrument, AMSR-E.

11


NEDT All channels meet the requirements and most of the channels

achieved the targets.

12

0

0.2

0.4

0.6

0.8

1

1.2

1.4

H V H V H V H V H V H V H V H V

6.9G 7.3G 10G 18G 23G 36G 89GA 89GB

AMSR-E on-orbit （2002/6-2003/1） AMSR2 on-orbit (2012/7) Spec. Target

0

0.2

0.4

0.6

0.8

1

1.2

Jul Aug Sep Oct Nov Dec Jan

NED

T [K

]

6.9GHz-H

6.9GHz-V

7.3GHz-H

7.3GHz-V

10GHz-H

10GHz-V

18GHz-H

18GHz-V

23GHz-H

23GHz-V

36GHz-H

36GHz-V

89GHzA-H

89GHzA-V

89GHzB-H


Gain and detector stability Gain and detector output level of all the channels are stable.

13

Detector output (HTS) Gain

0

50

100

150

200

250

300


Det

ect

or

ou

tpu

t [m

V]

6.9GHz-H

6.9GHz-V

7.3GHz-H

7.3GHz-V

10GHz-H

10GHz-V

18GHz-H

18GHz-V

23GHz-H

23GHz-V

36GHz-H

36GHz-V

89GHzA-H

89GHzA-V

89GHzB-H0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45


Gai

n [

mV

/K]

6.9GHz-H

6.9GHz-V

7.3GHz-H

7.3GHz-V

10GHz-H

10GHz-V

18GHz-H

18GHz-V

23GHz-H

23GHz-V

36GHz-H

36GHz-V

89GHzA-H

89GHzA-V

89GHzB-H


Gain variation over one orbit

14

0.2455

0.246

0.2465

0.247

0.2475

0.248

0.2485

0.249

0.246

0.2465

0.247

0.2475

0.248

0.2485

0.249

0.2495

0.25

0.2505

0.251

0:57 1:12 1:26 1:40 1:55 2:09 2:24 2:38

V-p

ol.

Gai

n [

mV

/K]

H-p

ol.

Gai

n[m

V/K

]

6GHz-H Gain 6GHz-V Gain

0.212

0.2125

0.213

0.2135

0.214

0.2145

0.215

0.2155

0.215

0.216

0.217

0.218

0.219

0.22

0.221

0.222

0.223

0:57 1:12 1:26 1:40 1:55 2:09 2:24 2:38

V-p

ol.

Gai

n [

mV

/K]

H-p

ol.

Gai

n[m

V/K

]


0.203

0.2035

0.204

0.2045

0.205

0.2055

0.206

0.2065

0.207

0.2755

0.276

0.2765

0.277

0.2775

0.278

0.2785

0.279

0:57 1:12 1:26 1:40 1:55 2:09 2:24 2:38

V-p

ol.

Gai

n [

mV

/K]

H-p

ol.

Gai

n[m

V/K

]


0.392

0.3925

0.393

0.3935

0.394

0.3945

0.395

0.3955

0.396

0.3965

0.397

0.3975

0.3365

0.337

0.3375

0.338

0.3385

0.339

0.3395

0.34

0.3405

0.341

0.3415

0:57 1:12 1:26 1:40 1:55 2:09 2:24 2:38

V-p

ol.

Gai

n [

mV

/K]

H-p

ol.

Gai

n[m

V/K

]


0.289

0.2895

0.29

0.2905

0.291

0.2915

0.292

0.2925

0.41

0.411

0.412

0.413

0.414

0.415

0.416

0.417

0:57 1:12 1:26 1:40 1:55 2:09 2:24 2:38

V-p

ol.

Gai

n [

mV

/K]

H-p

ol.

Gai

n[m

V/K

]23GHz-H Gain 23GHz-V Gain

0.28

0.2805

0.281

0.2815

0.282

0.2825

0.283

0.29

0.2905

0.291

0.2915

0.292

0.2925

0:57 1:12 1:26 1:40 1:55 2:09 2:24 2:38

V-p

ol.

Gai

n [

mV

/K]

H-p

ol.

Gai

n[m

V/K

]


0.122

0.123

0.124

0.125

0.126

0.127

0.128

0.129

0.13

0.118

0.119

0.12

0.121

0.122

0.123

0.124

0.125

0:57 1:12 1:26 1:40 1:55 2:09 2:24 2:38

V-p

ol.

Gai

n [

mV

/K]

H-p

ol.

Gai

n [

mV

/K]

89GHzA-H Gain 89GHzA-V Gain

0.114

0.115

0.116

0.117

0.118

0.119

0.12

0.121

0.113

0.114

0.115

0.116

0.117

0.118

0.119

0.12

0:57 1:12 1:26 1:40 1:55 2:09 2:24 2:38

V-p

ol.

Gai

n [

mV

/K]

H-p

ol.

Gai

n [

mV

/K]

89GHzB-H Gain 89GHzB-V Gain

(20120719 path191)


Spatial resolution

15

6.9GHz 7.3GHz 10GHz 18GHz 23GHz 36GHz 89GHzA 89GHzB

Nominal 61km 61km 41km 22km 26km 12km 5km 5km

H-pol. 65km 60km 40km 25km 25km - - -

V-pol. 65km 60km 40km 20km 20km - - -

6.9GHz 7.3GHz 10GHz 18GHz 23GHz 36GHz 89GHzA 89GHzB

Nominal 35km 35km 24km 13km 15km 7km 3km 3km

H-pol. 36km 36km 23km 14km 14km 10km 3.1㎞ 3.7㎞

V-pol. 36km 36km 23km 14km 14km 10km - 3.1㎞

Azimuth direction （half-power beamwidth）

Elevation direction （half-power beamwidth）

Elevation

Azimuth

Along Track

Footprint

Scan Direction

*The evaluation method is not applicable to high resolution channels since sampling gap

is large compared to spatial resolution.

Radiometric calibration

Flow of radiometric calibration

16

RFI removalLunar intrusion removal

OBS/CAL output count (raw data)

Observation DataCSM Data HTS Data

DC Gain/Offset

RFI removal

CSM Ta

HTS effective Bt

Deep Space Bt

Increased by PDL/STR

Increased by Earth radiation

HTS Pt measurements

HTS temperature correction

Linearity correction

MREF Ta

Brightness Temperature

Scan bias correction

Conversion to Bt

Detector input-output curve

Scan bias

Cross-polarization couplingMREF spill over ratio

computed

Detector output voltage

CSM spill over ratio

Linearity correction Receiver LinearityN/A

N/A

Ancillary Data

Constant

Analytical or Measured Value

Intermediate Data

Derived from OBS Data

CSM (Lunar intrusion)

17


20120826 Path 185A

234

234.5

235

235.5

236

236.5

237

237.5

238

154

154.5

155

155.5

156

156.5

157

157.5

158

1

87

17

3

25

9

34

5

43

1

51

7

60

3

68

9

77

5

86

1

94

7

10

33

11

19

12

05

12

91

13

77

14

63

15

49

16

35

17

21

18

07

18

93

HTS

Ou

tpu

t V

olt

age

[m

V]

CSM

Ou

tpu

t V

olt

age

[m

V]

Scan Number

CSM 0

CSM 1

CSM 3

CSM 3

CSM 4

CSM 5

CSM 6

CSM 7

CSM 8

CSM 9

CSM 10

CSM 11

CSM 12

CSM 13

CSM 14

CSM 15

CSM Avg.

HTS Avg.

Raw data Corrected data

Global CSM data with lunar intrusion

(36 GHz V)

After correction

155.2155.4155.6155.8

156156.2156.4156.6156.8

157157.2157.4157.6

1

81

16

1

24

1

32

1

40

1

48

1

56

1

64

1

72

1

80

1

88

1

96

1

10

41

11

21

12

01

12

81

13

61

14

41

15

21

16

01

16

81

17

61

18

41

19

21

CSM1

155.2155.4155.6155.8

156156.2156.4156.6156.8

157157.2157.4157.6

1

81

16

1

24

1

32

1

40

1

48

1

56

1

64

1

72

1

80

1

88

1

96

1

10

41

11

21

12

01

12

81

13

61

14

41

15

21

16

01

16

81

17

61

18

41

19

21

CSM1

North

South

CSM (RFI) Contaminated samples are detected, removed and linearly interpolated.

18


7.3 GHz V-pol.

Detected RFI Contaminated with RFI

CSM (Earth radiation)

19


Earth radiation

Feedhorn

CSMCSM

spillover

Deep Space (3 K)

MREF

Deep Space

Deep Space

CSM data(6.9 GHz H)

Earth radiation comes into CSM

backlobe (spillover) from MREF.

Increase of Antenna Temperature

ΔTc[K] = α×Tb[K]－β

Frequency Pol. α β

6.9 GHz V 0.33% 0.07 K

H 0.35% 0.07 K

7.3 GHz V 0.20% 0.04 K

H 0.30% 0.06 K

10, 18, 23, 36, 89GHｚ H/V N/A

Sing of coefficients is inconsistent

with algorithm in current Level-1

processing .

It will be revised in next version.

North

South

CSM (FOV interference)

20


View from CSM focal point

-1792

-1790

-1788

-1786

-1784

-1782

-1780

-1842

-1840

-1838

-1836

-1834

-1832

-1830

CSM 0

CSM 1

CSM 2

CSM 3

CSM 4

CSM 5

CSM 6

CSM 7

CSM 8

CSM 9

CSM 10

CSM 11

CSM 12

CSM 13

CSM 14

CSM 15

6GHz-H 6GHz-V

No detectable impact of FOV interference on CSM antenna temperature

Scan position

CS

M o

utp

ut co

un

t

HTS • Effective brightness temperature TH

TH = Tave - ΔThts

Tave ：physical temperature of HTS derived by averaging 10

measured temperature.

ΔThts:Bias estimated from an effect of reflection

21


Frequency Reflection

effect

Bias

Correction

ΔThts

6.925 GHz 0.79% 2.3K

7.3 GHz 0.74% 2.1K

10.65 GHz 0.50% 1.4K

18.7 GHz 0.27% 0.8K

23.8 GHz 0.21% 0.6K

36.5 GHz 0.13% 0.4K

89.0 GHz 0.05% 0.1K

3D analytical model for an effect of reflection

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

17

17.2

17.4

17.6

17.8

18

18.2

18.4

18.6

18.8

19

0:57 1:12 1:26 1:40 1:55 2:09 2:24 2:38

Max

. dif

fere

nce

［℃］

Pt-

sen

sor[℃］

2013/01/27 191D-191A

HTS TMP 1

HTS TMP 2

HTS TMP 3

HTS TMP 4

HTS TMP 5

HTS TMP 6

HTS TMP 7

HTS TMP 8

HTS TMP 9

HTS TMP 10

Average

Difference

Average among 10

measurements

to be revised

Non-linearity correction

22


quadratic approximation of non-linear relationship

between detector input power and detector output

voltage from measurements (6.9GHz H-pol.)

amount of detector non-linearity correction

(corrected TA)－(lineary calibrated TA)

at a temperature of 5℃

-5

-4

-3

-2

-1

0

1

2

3

4

5

0 50 100 150 200 250 300 350

No

n-l

ine

arit

y C

orr

ect

ion

[K

]

Antenna Temperature [K]

6.9G-H

6.9G-V

y = 90224x2 + 9715.3x + 60.637R² = 1

y = 84243x2 + 9665.1x + 60.94R² = 1

80

90

100

110

120

130

140

150

160

170

180

0 0.002 0.004 0.006 0.008 0.01 0.012

Vo

ut

[mV

]

Pin [mW]

6.9 GHz H-pol.

0℃

+10℃

多項式 (0℃)

多項式 (+10℃)

23


-5

-4

-3

-2

-1

0

1

2

3

4

5

0 50 100 150 200 250 300 350

No

n-l

ine

arit

y C

orr

ect

ion

[K

]


7.3G-H

7.3G-V

-5

-4

-3

-2

-1

0

1

2

3

4

5

0 50 100 150 200 250 300 350

No

n-l

ine

arit

y C

orr

ect

ion

[K

]


6.9G-H

6.9G-V

-5

-4

-3

-2

-1

0

1

2

3

4

5

0 50 100 150 200 250 300 350

No

n-l

ine

arit

y C

orr

ect

ion

[K

]


10G-H

10G-V

-5

-4

-3

-2

-1

0

1

2

3

4

5

0 50 100 150 200 250 300 350

No

n-l

ine

arit

y C

orr

ect

ion

[K

]


18G-H

18G-V

6.9 G 7.3 G

10 G 18 G

24


-5

-4

-3

-2

-1

0

1

2

3

4

5

0 50 100 150 200 250 300 350

No

n-l

ine

arit

y C

orr

ect

ion

[K

]


23G-H

23G-V

-5

-4

-3

-2

-1

0

1

2

3

4

5

0 50 100 150 200 250 300 350

No

n-l

ine

arit

y C

orr

ect

ion

[K

]


36G-H

36G-V

-5

-4

-3

-2

-1

0

1

2

3

4

5

0 50 100 150 200 250 300 350

No

n-l

ine

arit

y C

orr

ect

ion

[K

]


89GA-H

89GA-V

-5

-4

-3

-2

-1

0

1

2

3

4

5

0 50 100 150 200 250 300 350

No

n-l

ine

arit

y C

orr

ect

ion

[K

]


89GB-H

89GB-V

23 G 36 G

89 G

A

89 G

B

Scan bias correction (Ocean) Scan bias correction is applied to 6.9/7.3 and 10 GHz channels(except 10 GHz

H-pol.) with coefficient Cg derived from the long-term accumulated ocean

brightness temperature.

25


Correction coefficient Cg derived from

the ocean brightness temperature

0.99

1

1.01

1.02

1.03

1.04

1.05

0 27 54 81 108 135 162 189 216 243

Co

rre

ctio

n c

oe

ffic

ien

t C

g

Sample Number

6.9GHz-V Cg

6.9GHz-H Cg

7.3GHz-V Cg

7.3GHz-H Cg

10GHz-V Cg

raw data TA

corrected data TA’

TA’ = TA×Cg(i)

156

158

160

162

164

166

168

170

0 27 54 81 108 135 162 189 216 243

An

ten

na

Tem

per

atu

re [

K]

Sample Number

7.3 GHz V-pol.

76

78

80

82

84

86

88

90

0 27 54 81 108 135 162 189 216 243

An

ten

na

Tem

per

atu

re [

K]

Sample Number

7.3 GHz H-pol.

156

158

160

162

164

166

168

170

0 27 54 81 108 135 162 189 216 243

An

ten

na

Tem

per

atu

re [

K]

Sample Number

6.9 GHz V-pol.

76

78

80

82

84

86

88

90

0 27 54 81 108 135 162 189 216 243

An

ten

na

Tem

per

atu

re [

K]

Sample Number

6.9 GHz H-pol.

166

168

170

172

174

176

178

180

0 27 54 81 108 135 162 189 216 243

An

ten

na

Tem

per

atu

re [

K]

Sample Number

10 GHz V-pol.

80

82

84

86

88

90

92

94

0 27 54 81 108 135 162 189 216 243

An

ten

na

Tem

per

atu

re [

K]

Sample Number

10 GHz H-pol.

Scan bias correction (Land) • Cg derived from the ocean brightness temperature was applied to

the data of land area.

• The residual bias are shown.

TA’ overestimated in V-pol.

TA’ underestimated in H-pol.

Future tasks To revise the correction algorithm

To optimize the coefficients

for both ocean and land

26


TA’ = TA×Cg(i) + C0(i)

TA’ = TA×Cg(i)

260

262

264

266

268

270

272

274

276

0 27 54 81 108 135 162 189 216 243

An

ten

na

Tem

pe

ratu

re [

K]

Sample Number

6.9 GHz V-pol.

260

262

264

266

268

270

272

274

276

0 27 54 81 108 135 162 189 216 243

An

ten

na

Tem

pe

ratu

re [

K]

Sample Number

7.3 GHz V-pol.

262

264

266

268

270

272

274

276

278

0 27 54 81 108 135 162 189 216 243

An

ten

na

Tem

pe

ratu

re [

K]

Sample Number

10 GHz V-pol.

256

258

260

262

264

266

268

270

272

0 27 54 81 108 135 162 189 216 243

An

ten

na

Tem

pe

ratu

re [

K]

Sample Number

6.9 GHz H-pol.

256

258

260

262

264

266

268

270

272

0 27 54 81 108 135 162 189 216 243

An

ten

na

Tem

pe

ratu

re [

K]

Sample Number

7.3 GHz H-pol.

258

260

262

264

266

268

270

272

274

0 27 54 81 108 135 162 189 216 243

An

ten

na

Tem

pe

ratu

re [

K]

Sample Number

10 GHz H-pol.

raw data TA

corrected data TA’

need to be corrected?

Edge of the Earth

Spillover and Wide-angle sidelobe (Deep space)

27


Earth Deep Space STR

Frequency Deep Space

6.925 GHz 2.66%

7.3 GHz 3.29%

10.65 GHz 2.44%

18.7 GHz 1.99%

23.8 GHz 2.15%

36.5 GHz 2.21%

89.0 GHz 2.03%

Antenna pattern (6.9 GHz)

MREF Deep Space

Center of

MREF beam

Spillover

Antenna pattern of feedhorn (6.9 GHz)

to be revised

Wide-angle sidelobe

Conversion from TA into TB


28

V

VH

H

HV

V

VH

H

HV

VHV

H

V

H

H

V

V

H

H

V

VHVVHV

VHHH

B

B

AA

AA

11

1

111

1

1

11

1

111

1

1

　

　　

　　　

　　　　

　

　

CBHAVVHAHHHBH TBTATAT

CBVAVVVAHHVBV TBTATAT

Frequency AVV AHV BVTCB AHH AVH BHTCB

6.9 GHz 1.0304 -0.0031 -0.074 1.0303 -0.0030 -0.074

7.3 GHz 1.0435 -0.0095 -0.092 1.0418 -0.0078 -0.092

10 GHz 1.0277 -0.0028 -0.067 1.0275 -0.0025 -0.067

18 GHz 1.0229 -0.0026 -0.055 1.0229 -0.0025 -0.055

23 GHz 1.0247 -0.0027 -0.059 1.0250 -0.0031 -0.059

36 GHz 1.0250 -0.0025 -0.061 1.0251 -0.0025 -0.061

89 GHz (A) 1.0233 -0.0026 -0.056 1.0232 -0.0025 -0.056

89 GHz (B) 1.0230 -0.0022 -0.056 1.02313 -0.0024 -0.056

to be revised

Antenna losses (conduction and dielectric) emissivity of antenna surface ε < 0.25%

effective conductivity of VDA: 10MS/m

relative permittivity of SiO2 coating: 3.9

tanδ of SiO2 coating: 0.007

• Emissivity of 0.25% ⇒ Error of TB < 0.17K

29


-60

-50

-40

-30

-20

-10

0

10

20

30

2:00 2:10 2:20 2:30 2:40 2:50 3:00 3:10 3:20 3:30 3:40 3:50 4:00

Ph

ysic

al T

em

pe

ratu

re [℃

]

CSM TMP MREF TMP

-0.1

-0.05

0

0.05

0.1

0.15

0.2

2:00 2:10 2:20 2:30 2:40 2:50 3:00 3:10 3:20 3:30 3:40 3:50 4:00

Co

rre

ctio

n o

f B

t [K

]

CSM & MREF Reflection Loss Correction (Emissivity 0.0025)

Bt=80K Bt=150K Bt=290K Bt=340K

0.00%

0.05%

0.10%

0.15%

0.20%

0.25%

0.30%

0 15 30 45 60 75 90

Loss

/Em

issi

vity

Frequency [GHz]

εloss

σloss(pure Al)

Emissivity(pure Al)

σloss(sample)

Emissivity(sample)

Not corrected in

Level-1 processing

Antenna losses

31


PFM coupon BBM coupon

Vapor Deposited Aluminum


Summary of radiometric calibration

32

Item Amount of

correction Note

Cold calibration target

(CSM) < 1.2K

• an effect of the earth radiation from main reflector (< 0.35%) added

to TC

• not including occasional RFI and lunar intrusion removal

Hot calibration target

(HTS) < 2.3 K

• an effect of reflection (< 0.8%) subtracted from simple mean

temperature value for TH

• not including occasional low-frequency RFI removal

Input-output characteristic

(Detector non-linearity) < 5 K

• maximum at approximately 150 K

• large in 7-GHz bands compared to the other bands

Scan bias

(Scan non-uniformity) < 17 K

• proportional to antenna temperature (< 5%)

• only in scan edge of 7-GHz and 10-GHz bands

Spillover

（Cosmic background） < 11 K

• proportional to antenna temperature (< 3.3% including an effect of

cosmic background from wide-angle sidelobe of MREF)

Cross-polarization < 1 K • proportional to difference between TA of H-pol. and TA of V-pol.

Antenna loss N/A

• radiation from MREF and CSM surface (emissivity < 0.25% )

• error in antenna temperature due to the antenna loss < 0.17 K

(assuming that the surface characteristics of CSM is identical to

that of MREF)

Random Noise N/A • NEΔT, ΔG/G, 1/f noise

• circuit noise, quantization noise

Is there anything else we have to take into account?

Geometric calibration

Summary of geometric calibration • Geolocation parameters were corrected based on image matching between

observed Tb data and coastline database.

offnadir angle

AMSR2 SU alignment angle (Roll, Pitch, and Yaw)

relative registration coefficients between 89 GHz A-channel and other frequency

channels.

• Geometric error (RMSE) of each channel is within the half of each spatial

resolution.

33

Frequency

[GHz] Geometric Error

（RMSE） Along-track

Direction

Azimuth

Direction

6.9 10.2km 8.9km

7.3 9.5km 8.7km

10 6.5km 6.8km

18 3.8km 3.9km

23 3.3km 3.9km

36 2.3km 3.5km

89(A) 1.3km 1.1km

89(B) 1.4km 1.0km

Elevation

Azimuth

Along Track

Footprint

Scan Direction

Geometric calibration

Geometric error (89 GHz A-Scan)

34

y = 0.0003x - 0.0664-2

-1

0

1

2

0 100 200 300 400 500

Pixel(1pixel=10.227km)

Sample Number

89 GHz A-channel AT direction

y = 0.0002x + 0.0018-2

-1

0

1

2

0 50 100 150 200 250 300 350 400 450 500


Sample Number

89 GHz A-channel AT direction

y = 0.0005x - 0.0858-2

-1

0

1

2

0 50 100 150 200 250 300 350 400 450 500

Pixel

(1pixel=4.586km)

Sample Number

89 GHz A-channel AZ direction

y = 0.0005x - 0.0858-2

-1

0

1

2

0 100 200 300 400 500


Sample Number

89 GHz A-channel AZ direction

Ascending

Descending

Along track direction

(1[pixel] = 10[km])

Scan azimuth direction

(1[pixel] = 4.5[km])

Future Tasks

Ver. 1.1 of AMSR2 Level-1 products is to be released soon.

Continuous calibration activities to improve Tb and geolocation

accuracy by using long-term data.

Intercalibration in cooperation with JMA, NOAA, X-CAL team

and others. (Positive biases of AMSR2 Tb have been reported.)

Understanding root cause of the difference between Tb of

AMSR2 and other instruments from the viewpoint of

engineering.

35

Comparison with other

instruments The following information and evidences are very useful to analyze the root

cause of the difference.

I would appreciate if you could tell me available information sources or

contact person.

36

Item TMI1) Windsat2) SSMI/S3) AMSR2 GMI

Cold calibration target

(CSM) < 1.2K

Hot calibration target

(HTS) < 2.3 K

Input-output characteristic

(Detector non-linearity) < 0.1% ? < 5 K

Scan bias

(Scan non-uniformity) < 17 K

Feedhorn spillover < 10 K

Wide-angle sidelobe < 0.2K

Cross-polarization < 1 K

Antenna loss < 11 K ? < 2 K ?

at 50G

N/A

（< 0.17 K ）

other -

Thank you

37

Documents

AMSR2 characterization and calibration