Preparation for Vicarious Calibration of SMOS using Takelimgan Sand Desert

1. Preparation forVicarious Calibration of SMOS using Takelimgan Sand Desert Weiguo ZHANG, Ji WU, Heguang LIU, Chuandong XU, Dihui LI, Hao LIU, Jingshan JIANG

2. Contents 1. Revisit of AMSR-E data over the desert 2. The first Takelimgan field experiment 3. Consideration for commissioning phase campaign

3. AMSR-E data over the desert (AMSR-E data nicely provided by NSIDC.org by ftp) Stdev of errors: V Pol. 0.98K Stdev of errors: H Pol. 1.40K Data of the 2nd half year of 2005,10GHz The same dataset as used in optimization

4. Calibration AMSR-E data over the desert Data of the 2nd half year of 2005 Comparison of observed and simulated Tb AFTER calibration of H Pol. 10GHz Bias: -0.51083 Stdev of Errors: 0.82356K Comparison of observed and simulated Tb BEFORE calibration of H Pol. 10GHz (Stdev of errors: H Pol. 1.40K)

5. 250 2006 whole year H pol. 240 Simulation Something Wrong! 230 220 Something Wrong! 220 230 240 250 AMSRE Observation Calibration AMSR-E data over the desert Data of the whole year of 2006 More scattered Less scattered after calibration The Simulation method and calibration formula can be extended in time scale readily provided the instrument is stable.

6. Something Wrong Here! Quick Response to Spaceborne Radiometer Behavior

7. Can this simulation method and parameters be extended to other frequencies? 6.9GHz data simulated with the same method and parameters as for 10GHZ V. Pol. H. Pol.

8. Can this simulation method and parameters be extended to other frequencies? 19GHz data simulated with the same method and parameters as for 10GHZ V. Pol. H. Pol.

9. Implication to SMOS Cal/Val Activities • By excluding rainy days and obviously unreasonable observations, Tb of the desert can be simulated with an accuracy within 1K both for V and H pol. Currently at 10GHz. L band is supposed to be more stable. • Some unreasonable fluctuation (such as that exists in AMSR-E H pol.) can be identified and calibrated. Strange behavior of the sensor can be easily identified. • The simulation, calibration method and parameters can be readily extended in time scale. An intensive commission phase activities can do very much works to monitor its whole life cycle. • The simulation, calibration parameters for one frequency should not be extended to other frequencies without further investigation. But it seems the methods can be readily adopted by other frequencies. Investigation specially designed for L band is urgently needed.

10. The first Takelimgan field experiment • The experiment is carried out during 20/07/2007-22/08/2007, actual works was done during 25/07/2007-11/08/2005, 18 days. • The main purpose of the experiment is to measure soil moisture profile and distribution in an extent that can represents an average status near the center of the desert. Soil temperature profile is measured for obviously reason. • Two frequencies(6.6, 10.7GHz) radiometer is used to measure Tb of the desert in order to find what would be necessary and important with an L band campaign in mind.

11. Partner with tough job

12. Background info about the site

13. Sand Dunes

14. Soil moisture profile measurement

15. Soil temperature profile measurement Calibration curves

16. Soil Moisture and temperature sample points

17. Radiometer Setup

18. Ground Truth

19. Data Process ongoing

20. Consideration for Commissioning phase Campaign

21. Multiple angular simulation Roughness not considered

22. 50Km 50Km Commissioning phase campaign Three sets of Soil temperature profile sensors at every points. (100 sets in all, 10 for backup) Equipped before radiometer Operation. Data should be Recorded by automatic recorder. Wire based data recorder is preferred. Soil moisture profile beyond 2 m Should be investigated. Truck mounted radiometer needs to continuously observe sand dunes with different observation angle, azimuth angle and position at every points for two days. All 90 points may take 2 months to complete. Then tower observation. After that, soil temperature profile data should be collected from the data recorder once a week until commissioning phase finished. 50Km It may cost 3million RMB$. The scale may not be exact.

23. L-band Radiometer Architecture Prospect System Parameter: • Central Freq： 1.4135 GHz • 3db Bandwidth： 19 MHz （1.404~1.423 GHz） • Noise Figure： 3 dB • Antenna Beamwidth: ～15o ( In development ) Nicely provided by Hao LIU

24. Summary • We aim at provide an absolute brightness temperature tie point to be used for SMOS calibration, including long term and short term, especially at hot end. The accuracy is expected to be 1K according to AMSR-E analysis. It is possible but much works need to do. • Intensive commissioning phase campaign with an stable and accurate L band radiometer is necessary for absolute brightness temperature evaluation. Drift, unreasonable fluctuation during the whole life cycle can be readily monitored after a successful campaign.

25. Thanks for attention!