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Barcelona, July 25, 2007 WATER HM Meeting Radiometer Concepts for Coastal and Inland Wet Path Delay Estimation Shannon Brown Jet Propulsion Laboratory Shannon.T.Brown@jpl.nasa.gov
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Barcelona, July 25, 2007 WATER HM Meeting Radiometer Land Contamination Land contamination can be divided into three categories Far sidelobe contamination Near sidelobe contamination Main beam contamination Near sidelobes Mainbeam Far sidelobes Far sidelobe contamination Correctable to acceptable levels (~ 1mm) Near sidelobe contamination More difficult, but correction is possible (~2-4 mm) Main beam contamination Very difficult to correct (20- 40 mm)
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Barcelona, July 25, 2007 WATER HM Meeting Main Beam Contamination Along track averaging can improve coastal approach for preferred land/ground track orientations Additional improvements may be made through correction algorithms based on pattern weighted main beam land fractions 10 km approach at Harvest estimated for AMR ~20 km approach estimated for worst case for AMR
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Barcelona, July 25, 2007 WATER HM Meeting Radiometer Concepts Option 1: Maintain traditional channel set, but increase antenna dimensions Real aperture Synthetic aperture > 2.5 m aperture required for < 5 km resolution
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Barcelona, July 25, 2007 WATER HM Meeting Option 1 NASA Aquarius Heritage for 2.5 m reflector Lightweight Rainfall Radiometer – aircraft heritage for synthetic aperture radiometer technology Visible Camera LRR
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Barcelona, July 25, 2007 WATER HM Meeting Radiometer Concepts Option 1: Maintain traditional channel set, but increase antenna dimensions Real aperture Synthetic aperture > 2.5 m aperture required for < 5 km resolution Pros: Proven retrieval algorithm Retrievals in all non-precipitating conditions High sensitivity to PD over the range of PDs Cons: Complications from large real aperture required Synthetic aperture technique proven in aircraft demonstration, but not yet in space Difficult to get PD in inland areas (i.e. rivers)
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Barcelona, July 25, 2007 WATER HM Meeting Move to Higher Frequency Maintain 18-34 GHz channel set for open ocean retrievals Maintain AMR heritage 1m reflector Option 2: Include 1-2 higher frequency window channels for coastal PD extrapolation Option 3: Include temperature and vapor sounding channels for PD retrievals over land and ocean 22.235 GHz (H 2 O) 55-60 GHz (O 2 ) 118 GHz (O 2 ) 183.31 GHz (H 2 O)
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Barcelona, July 25, 2007 WATER HM Meeting Option 2 Add 1 or 2 channels between 90-150 GHz to improve the extrapolation of PD from the last uncontaminated ocean pixel to the coast
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Barcelona, July 25, 2007 WATER HM Meeting Option 2 Modeled Brightness Temperature to PD and CLW 23.8 GHz 90 GHz 130 GHz160 GHz 90 GHz T B ~8x more sensitive to CLW than 23.8 GHz T B Sensitivity to high PD decreases with frequency 10 km 2.6 km 2.1 km1.5 km dT B /dPD
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Barcelona, July 25, 2007 WATER HM Meeting Option 2 Add 1 or 2 channels between 90-150 GHz to improve the extrapolation of PD from the last uncontaminated ocean pixel to the coast Pros: Relatively small perturbation to add two channels in this frequency range These channels will have < 5 km resolution with 1 m reflector Cons: These channels will loose sensitivity to PD for high PD values Performance can be affected in variable cloud conditions near coast Not likely to be able to get PD in inland areas (i.e. rivers)
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Barcelona, July 25, 2007 WATER HM Meeting Option 3 Add temperature and water vapor sounding channels to retrieve PD over land and coast (channels near 50 or 118 GHz and channels near 183 GHz) Will likely need 2-3 temperature sounding channels and 4 water vapor sounding channels 183 + 1 183 + 3 183 + 7 166 Height (km) 60 GHz Temperature Weighting Functions 183 GHz Water Vapor Weighting Functions
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Barcelona, July 25, 2007 WATER HM Meeting Option 3 Add temperature and water vapor sounding channels to retrieve PD over land and coast (channels near 50 or 118 GHz and channels near 183 GHz) Pros: Should be able to retrieve PD over land or water High resolution < 5 km Cons: Reduced accuracy in clouds Reduced sensitivity to PD in moist conditions Uncertain with what accuracy this can be done
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Barcelona, July 25, 2007 WATER HM Meeting Conclusions Option 1: Large antenna Scientific Risk: Low Engineering Risk: Medium Option 2: Higher frequency window channels Scientific Risk: Medium Engineering Risk: Low Option 3: Temperature and water vapor sounding channels Scientific Risk: Medium Engineering Risk: Medium
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