Aquarius Scatterometer Stability

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1 Aquarius Scatterometer Stability Greg Neumann, Simon Yueh, Alex Fore, Adam Freedman, Akiko Hayashi, Wenqing Tang 30 Oct 2012

2 Ancillary Data Correlations With Scatterometer Sigma0 Correlation calculated between [Sigma0-Expected sigma0] and the following parameters: Atmospheric Transmittance Surface Pressure Surface Temperature Wind Speed Scatterometer Faraday Rotation Radiometer Faraday Rotation Cloud Water Antenna Temperatures (avg of 8) Sea Surface Salinity Wave-Watch 3 Correlation calculated over various time scales from 7 days to entire mission. Correlations performed for sub-sets of the data: Ascending, Descending, Ascending and Descending Beam 1, Beam 2, Beam 3, All 3 Beams Correlations over longer periods of time give lower correlation coefficients.

3 Scatterometer Correlations Parameter All data H All data V Max over 7 days H Max over 7 days V Scatterometer Faraday Rotation Radiometer Faraday Rotation Atmospheric Transmittance Surface Pressure Surface Temperature Wind Speed Cloud Water Antenna Temperatures Sea Surface Salinity Wave Watch

4 Scatterometer Stability Double Difference - Establish a model function, difference the measured Sigma0 from the expected Sigma0. Generate Images to observe where the model function has more error. Plot average [s0-expected s0] over the mission. Daily average, 7-day averages Mode, 7-day average of mode. Engineering information LBC, Gain from CND

5 Notes V1.3.5 data used land fraction limit used to observe ocean only. Slight increase in scatterometer sigma0 is observed over the mission using 3 different methods of accumulation (each shown with a running average of 28 days): Differencing Sigma0 and Expected Sigma0 in db. Differencing Sigma0 and Expected Sigma0 as natural numbers and converting to db at the end. Tracking the mode (most likely value of the pdf) The following images show the spatial average and standard deviation of the data.

6 Average (s0 Expected s0) HH

7 Average (s0 Expected s0) VV

8 Std Dev (s0 Expected s0) HH

9 Std Dev (s0 Expected s0) VV

10 [s0 Expected s0] HH pol JPL V1.3.5 no rain, WW Avg 28 apd Beam 1 Avg 28 apd Beam 2 Avg 28 apd Beam 3 Avg 28 asc Beam 1 Avg 28 asc Beam 2 Avg 28 asc Beam 3 Avg 28 des Beam 1 Avg 28 des Beam 2 Avg 28 des Beam db :00: :00: :00: :00: :00: :00: :00:00

11 [s0 Expected s0] VV pol JPL V1.3.5 no rain, WW Avg 28 apd Beam 1 Avg 28 apd Beam 2 Avg 28 apd Beam 3 Avg 28 asc Beam 1 Avg 28 asc Beam 2 Avg 28 asc Beam 3 Avg 28 des Beam 1 Avg 28 des Beam 2 Avg 28 des Beam db :00: :00: :00: :00: :00: :00: :00:00

12 Mode of [s0 Expected s0] JPL V1.3.5 no rain, WW3 Avg 28 HH Beam 1 Avg 28 HH Beam 2 Avg 28 HH Beam 3 Avg 28 VV Beam 1 Avg 28 VV Beam 2 Avg 28 VV Beam 3 (db) :00: :00: :00: :00: :00: :00: :00:00

13 Mode of [s0 Expected s0] JPL V1.3.5 Avg 28 HH Beam 1 Avg 28 HH Beam 2 Avg 28 HH Beam 3 Avg 28 VV Beam 1 Avg 28 VV Beam 2 Avg 28 VV Beam 3 (db) :00: :00: :00: :00: :00: :00: :00:00

14 Avg/Mode of NCEP Wind Speed JPL V1.3.5 no rain, WW3 Avg 28 Beam 1 Avg 28 Beam 2 Avg 28 Beam 3 Mode 28 Beam 1 Mode 28 Beam 2 Mode 28 Beam 3 (m/s) :00: :00: :00: :00: :00: :00: :00:00

15 Scatterometer Block Diagram (simplified) BPF: Fc=1260 MHz To ADC BPF BW=4 MHz Frequency down-converter Phase Locked Multiplier Frequency up-converter Reference Digital Oscillator Chirp Generator Phase Locked Multiplier Limiter + Step Low noise attenuator amplifier Power supply Solid State power Amplifier Loop-Back switch Loop-Back attenuator 1H 2H 3H Beam switch Test load 1V To radiometer Diplexer Test Port Noise Diode Directional coupler H Ortho-mode Transducer (OMT) V Diplexer To radiometer Scatterometer Back End (SBE) calibrated Not calibrated by Loopback by Loopback Scatterometer Front End (SFE) 2V 3V

16 Scatterometer Loop-Back Cal Stability B1HV B1VV B1VH B1HH B2HV B2VV B2VH B2HH B3HV B3VV B3VH B3HH Power (db) Daily Average :00: :00: :00:00 UTC Time :00: :00:00

17 Scatterometer CND Gain Gain Beam 1V (db) Gain Beam 2V (db) Gain Beam 3V (db) Gain (db) Daily Average :00: :00: :00: :00: :00:00 UTC Time

18 Scatterometer LBC/CND Gain Ratio Beam 1 Beam 2 Beam Ratio (db) Daily Average :00: :00: :00:00 UTC Time :00: :00:00

19 LBC/(CND Gain) Stability Possible contributors to LBC/(CND Gain) change: Transmit Power is changing downward. (Sigma0 would not be affected, SNR would increase) Loop-back calibration loss is changing upward. (Sigma0 would increase, SNR would not be affected) The CND The Beam Switch Cable loss, connectors between the CND and the scatterometer. Diplexers Scatterometer step attenuator Something else? The relative change in LBC/CND is nearly the same for all 3 Scatterometer Beams using 3 physically different paths, each of which contains: A different CND Different Front end cables, connectors A different Diplexer The Beam Switch (through different paths) Most likely cause is a common element behind the beam switch.

20 [s0 Expected s0] HH pol JPL V1.3.5 no rain, WW apd Beam A asc Beam A des Beam A LBC/CND (Relative) db :00: :00: :00: :00: :00: :00: :00:00

21 [s0 Expected s0] VV pol JPL V1.3.5 no rain, WW apd Beam A asc Beam A des Beam A LBC/CND (Relative) db :00: :00: :00: :00: :00: :00: :00:00

22 [s0 Expected s0] HH pol JPL V1.3.5 no rain, WW day Avg apd Beam 1 1 day Avg apd Beam 2 1 day Avg apd Beam 3 1 day Avg asc Beam 1 1 day Avg asc Beam 2 1 day Avg asc Beam 3 1 day Avg des Beam 1 1 day Avg des Beam 2 1 day Avg des Beam 3 LBC/CND (relative) db :00: :00: :00: :00: :00: :00: :00:00

23 [s0 Expected s0] VV pol JPL V1.3.5 no rain, WW day Avg apd Beam 1 1 day Avg apd Beam 2 1 day Avg apd Beam 3 1 day Avg asc Beam 1 1 day Avg asc Beam 2 1 day Avg asc Beam 3 1 day Avg des Beam 1 1 day Avg des Beam 2 1 day Avg des Beam 3 LBC/CND (relative) db :00: :00: :00: :00: :00: :00: :00:00

24 Conclusion Slight increase in sigma0 over the mission observed using double-difference. Most of the increase toward the beginning of the mission (2 to 3 months). There may be a contribution to Sigma0 stability (.05 db) from the instrument. This needs further investigation. If confirmed, may recommend an exponential drift correction for the first 2 to 3 months of data.

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