1. WindSat:
Passively Measuring
Ocean Vector Winds
(and other things)
Ian S. Adams
Michael H. Bettenhausen
Peter W. Gaiser
Li Li
Remote Sensing Physics Branch
Naval Research Laboratory
1

2. Mission Status
• Demonstrate passive wind
vector measurements from
space
• Risk reduction for
NPOESS MIS
• 7 years of successful ops
• NRL Responsible for
Science, Payload
Development, Mission
Management, Vehicle
Integration, and Cal/Val
2

3. WindSat Band Descriptions
Freq. BW EIA IFOV
Channels
11 (GHz)
feedFeedhorn Location Requirements
horns (MHz) (deg) (km)
6.8 v/h 125 54.0 39 x 71
Feed Freq.
(GHz)
6.8
22 measured
Polarization
V/H
X
Location
0.206
Y
Location
9.963
Z
Location
0.261
Notes:
10.7 v/h, +/– 45, lc/rc
Feed Bench View From Main Reflector
300 50.3 25 x 38
10.7
10.7
antenna ±45
CP
3.137
2.995
4.492
0.000
-0.033
0.182
18.7Bench Coordinate45, lc/rc GHz 750
Feed v/h, +/– Origin At 37 55.9 16 x 27
CP Horn Phase Center
10.7
18.7
temperatures
V/H
±45
3.137
-2.157
-4.492
2.712
-0.033
-0.013
23.8 Sets Located on Four “Great
Horns v/h 500 53.5 20 x 30
18.7 CP -2.202 0.000 -0.216 Circles” Resulting in Four Different EIA’s
18.7 V/H -2.157 -2.712 -0.013 37.0 Hornv/h, +/– 45, lc/rc
Offset Lateral Locations Not Critical2000 53.5 8 x 13
23.8 V/H 0.448 -8.102 0.413 As Long As They Remain on, or Can Be
37.0 ±45 0.034 2.249 0.036 Adjusted to, Great Circles
37.0 CP 0.000 0.000 0.000
37.0 V/H 0.034 -2.249 0.036
+ XF
Warm Cold
Load 10.7GHz ±45 10.7GHz CP 10.7GHz V/H Load
Side Side
6.8GHz V/H
37GHz CP
+ YF - YF
37GHz ±45 0,0 37GHz V/H
23.8GHz V/H
18.7GHz ±45 18.7GHz CP 18.7GHz V/H
990922_WS_CDR_AntSys.16
Spin Axis - XF
3

4. WindSat Data Usage
• Assimilation
• NOGAPS
• NCEP
• UK Met Office
• ECMWF
• Testing
• Tropical Cyclone
Monitoring
• NRL Monterey
• CIMSS (UW-Madison)
• GPM Satellite Cross-
Calibration Work
4

5. Dr. Jones and WindSat
• Involvement in early development
• Systems Requirement Review
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• Active participation in launch / post-launch activities
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6. WindSat Warm Load Anomaly
PRT PRT PRT
18.7 37 10.7
Sun reflecting into warm
load produces thermal
gradients in the warm load
not a problem during Feb.,
Mar., Oct. and Nov.
worst in late May through
mid July
CANISTER DECK (Silver teflon tape)
• PRT measured warm load temperature is not what
the radiometer measures
MHB - IGARSS 2007.
• Details of the problem found in Twarog (2006)
• Correction a function of solar beta angle
6

7. Cold Calibration Intrusions
• Space-based RF
contamination from
geostationary satellites
• 10.7 GHz
• 18.7 GHz
• Lunar contamination
occurs with lunar cycle
• 3-4 days in duration
• Centered on full moon
• Statistical detection and
correction
7

8. Along Scan Variations
• Result of changes in the field of view of the feeds
• Power from the Earth scene, CMB, spacecraft, sensor
• Scan dependent spillover and bias corrections
• TA = ηT'A + (1 – η) TCMB + β
• TA is the antenna temperature
• η is spillover
• TCMB is cold space temperature
• β is a constant bias term
• Changes in cross polarization may also be present
• Difficult to correct accurately
• Tp ≈ (1 – a) T'Ap + a(T'Av – T'Ah) where a << 1
• Analysis must consider EIA variations
8
• Pitch offset = 0.19o and roll offset = -0.14o

9. Vicarious Calibration
• Minimum ocean Tb for cold calibration temperature
• Ruf et al. (2000, 2006); McKague et al. (2008, 2009)
• Tropical Forest as hot calibration reference
• Brown and Ruf (2005); Mo (2007)
• Two months of data
• Over 4000 orbits
Tropical Forest
Mask for 18.7 GHz
9

10. Pitch Maneuvers
• Similar to maneuver
performed with TRMM
480 IEEE TRANSACTIONS O
• WindSat pitched +/-45o
• Main reflector views
cosmic microwave
background (CMB)
• Useful for diagnosing
azimuthally-dependent
radiometer variations
Jones et al. 2006
Fig. 11. Locus of main beam pointing into space during the positive 45 pitch
• Isotropic CMB removes
EIA dependence
maneuver. Also shown are the azimuth blockage ranges for the hot and cold
calibration loads.
Fig. 14.
measure
10 swath e
south to

11. Along-Scan Bias: Vicarious versus
NES et al.: DEEP-SPACE CALIBRATION OF THE WINDSAT RADIOMETER
18.7 3rd Stokes, Forest, Vicarious
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11

12. WindSat Retrievals
• Ocean retrievals
• Three Resolutions
• Low: 50 km x 71 km
• Medium: 35 km x 53 km
• High: 25 km x 35 km
• Near-surface vector winds
• Water vapor
• SST
• Cloud
• Precipitation (GPROF)
• Soil moisture
• Sea ice concentration Parma
12

13. WindSat Ocean Retrievals
• Physically-based 10.7 GHz at 8 m/s Wind Speed
Directional Dependence (K)
0.6
• Parameterized forward
atmospheric RTM
0.4 Tv
Th
0.2
• Empirically-tuned sea-
surface emissivity model
0
-0.2
-0.4
• Optimal estimator 0 90 180 270
Relative Wind Direction (degrees)
360
•
Directional Dependence (K)
Minimize cost function 0.6
T3
0.4
• 0.2
T4
• Goodness of fit
0
-0.2
• -0.4
0 90 180 270 360
• Depends on # of channels Relative Wind Direction (degrees)
• Depends on # of retrieved
parameters
13

14. WindSat Extratropical Observation
Surface model tuned for
high wind speed retrievals
QuikSCAT
0352 UTC
12 January 2008
WindSat
0245 UTC
12 January 2008
14

15. WindSat Wind Vectors
Low Resolution High Resolution
15

16. Another Use for χ2
10.7 GHz
18.7 GHz
10.7 GHz 10.7 GHz
P(χ2)0.3
16

17. Soil Moisture
United States
Global soil moisture patterns are consistent with
climate zones and precipitation climatology
France
Mongolia
17

18. Summary
Hurricane Fabian
• Consistent calibration
across the scan
High Resolution (No 6.8 GHz)
• No inter-calibration with
other instruments
• Absolute calibration with
RTM at EDR level
• Investigating Tb stability
over mission
• Constant RFI monitoring
• Can mitigate in ocean
retrievals
• Produce a number of
EDRs
18

19. WindSat Related Talks
Title: WINDSAT SOIL MOISTURE AND VEGETATION WATER CONTENT OBSERVATIONS ASSOCIATED WITH THE 2003 EUROPEAN
HEAT WAVE
Topic: Land: Soils and Soil Moisture
Session: Soil Moisture and Vegetation Characterization Using Microwave I
Time: Friday, July 30, 14:55 - 16:00
Authors: Li Li, Sonia Seneviratne, Peter W. Gaiser, Gerald Nedoluha
Title: Time Evolution and Spatial Distribution of Ocean-Reflected Radio-Frequency Interference During the WindSat Era
Topic: Invited Sessions: Frequency Allocation for Remote Sensing and RFI Mitigation for Microwave Radiometry
Session: Frequency Allocation for Remote Sensing and RFI Mitigation for Microwave Radiometry
Time: Wednesday, July 28, 13:35 - 15:15
Authors: Ian S. Adams, Michael H. Bettenhausen, Peter W. Gaiser, William Johnston
Title: COMPARISON OF VEGETATION WATER CONTENT ESTIMATES FROM WINDSAT AND MODIS
Topic: Land: Soils and Soil Moisture
Session: Remote Sensing of Soil and Vegetation: Applications II
Time: Friday, July 30, 09:40 - 10:45
Authors: E. Raymond Hunt Jr., Li Li, M. Tugrul Yilmaz, Thomas Jackson
Title: ANTICIPATING THE VIIRS AND MIS SENSORS ABOARD NPOESS
Topic: 30th Anniversary: 30th Anniversary
Session: Education and Remote Sensing Posters
Time: Tuesday, July 27, 14:55 - 16:00
Authors: Thomas Lee, Jeffrey Hawkins, Arunas Kuciauskas, Kim Richardson, Michael H. Bettenhausen, Ian S. Adams, Steven D. Miller
19

20. WindSat Related Talks
Title: CORRECTION ON AMSR-E AND WINDSAT SST FOR LONG TERM TREND
Topic: Sensors and Platforms: Radiometer Instruments and Calibration
Session: AMSR-E II
Time: Thursday, July 29, 15:40 - 17:20
Authors: Akira Shibata
Title: CHARACTERIZATION OF K-BAND RADIO FREQUENCY INTERFERENCE FROM AMSR-E, WINDSAT AND SSM/I
Topic: Sensors and Platforms: Radiometer Instruments and Calibration
Session: Airborne and Spaceborne Measurements of Radio-Frequency Interference
Time: Wednesday, July 28, 15:40 - 17:20
Authors: Darren McKague, John Puckett, Christopher Ruf
Title: WINDSAT RETRIEVAL OF OCEAN SURFACE WIND SPEEDS IN TROPICAL CYCLONES
Topic: Student Paper Contest: Student Paper Contest
Session: Student Contest II
Time: Wednesday, July 28, 10:25 - 12:05
Authors: Amanda Mims, Rachael Kroodsma, Christopher Ruf, Darren McKague
Title: INTERSATELLITE CALIBRATION OF MICROWAVE RADIOMETERS FOR THE GLOBAL PRECIPITATION MEASURING MISSION
Topic: Invited Sessions: Microwave scatterometry, radiometery and ocean applications (honoring Dr. W. Linwood Jones)
Session: Microwave Scatterometry, Radiometry and Ocean Applications (Honoring Dr. W. Linwood Jones) I
Time: Tuesday, July 27, 13:35 - 15:15
Authors: Thomas Wilheit
Title: INTERCALIBRATION OF AMSR-E AND WINDSAT BRIGHTNESS TEMPERATURE MEASUREMENTS OVER LAND SCENES
Topic: Sensors and Platforms: Radiometer Instruments and Calibration
Session: AMSR-E I
Time: Thursday, July 29, 13:35 - 15:15
Authors: Thomas Meissner, Frank Wentz
20

21. Thank You Dr. Jones!
21