Barcelona, July 25, 2007 WATER HM Meeting Radiometer Concepts for Coastal and Inland Wet Path Delay...
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Transcript of Barcelona, July 25, 2007 WATER HM Meeting Radiometer Concepts for Coastal and Inland Wet Path Delay...
Barcelona, July 25, 2007WATER HM Meeting
Radiometer Radiometer Concepts for Coastal Concepts for Coastal and Inland Wet Path and Inland Wet Path
Delay EstimationDelay Estimation
Shannon Brown
Jet Propulsion Laboratory
Barcelona, July 25, 2007WATER HM MeetingRadiometer 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)
Barcelona, July 25, 2007WATER HM MeetingMain 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
Barcelona, July 25, 2007WATER HM MeetingRadiometer Concepts
Option 1: Maintain traditional channel set, but increase antenna dimensions
Real aperture Synthetic aperture > 2.5 m aperture required for < 5 km resolution
Barcelona, July 25, 2007WATER HM MeetingOption 1
NASA Aquarius Heritage for 2.5 m reflector
Lightweight Rainfall Radiometer – aircraft heritage for synthetic aperture radiometer technology
Visible Camera
LRR
Barcelona, July 25, 2007WATER HM MeetingRadiometer 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)
Barcelona, July 25, 2007WATER HM MeetingMove 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 (H2O)
55-60 GHz (O2)118 GHz (O2)
183.31 GHz (H2O)
Barcelona, July 25, 2007WATER HM MeetingOption 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
Barcelona, July 25, 2007WATER HM MeetingOption 2
Modeled Brightness Temperature to PD and CLW
23.8 GHz 90 GHz
130 GHz 160 GHz
90 GHz TB ~8x more sensitive to CLW than 23.8 GHz TB
Sensitivity to high PD decreases with frequency
10 km 2.6 km
2.1 km 1.5 km
dTB/dPD
Barcelona, July 25, 2007WATER HM MeetingOption 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)
Barcelona, July 25, 2007WATER HM MeetingOption 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
Hei
gh
t (k
m)
60 GHz Temperature Weighting Functions 183 GHz Water Vapor
Weighting Functions
Barcelona, July 25, 2007WATER HM MeetingOption 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
Barcelona, July 25, 2007WATER HM MeetingConclusions
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