Title: Radiometer Concepts for Coastal and Inland Wet Path Delay Estimation
1- Radiometer Concepts for Coastal and Inland Wet
Path Delay Estimation - Shannon Brown
- Jet Propulsion Laboratory
- Shannon.T.Brown_at_jpl.nasa.gov
2Radiometer Land Contamination
- Land contamination can be divided into three
categories - Far sidelobe contamination
- Near sidelobe contamination
- Main beam contamination
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)
Mainbeam
Near sidelobes
3Main 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
20 km approach estimated for worst case for AMR
10 km approach at Harvest estimated for AMR
4Radiometer Concepts
- Option 1 Maintain traditional channel set,
but increase antenna dimensions - Real aperture
- Synthetic aperture
- gt 2.5 m aperture required for lt 5 km resolution
5Option 1
Lightweight Rainfall Radiometer aircraft
heritage for synthetic aperture radiometer
technology
Visible Camera
LRR
- NASA Aquarius Heritage for 2.5 m reflector
6Radiometer Concepts
- Option 1 Maintain traditional channel set,
but increase antenna dimensions - Real aperture
- Synthetic aperture
- gt 2.5 m aperture required for lt 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)
7Move 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
8Option 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
9Option 2
- Modeled Brightness Temperature to PD and CLW
- 90 GHz TB 8x more sensitive to CLW than 23.8
GHz TB - Sensitivity to high PD decreases with frequency
23.8 GHz
90 GHz
2.6 km
10 km
dTB/dPD
130 GHz
160 GHz
2.1 km
1.5 km
10Option 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 lt 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)
11Option 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
60 GHz Temperature Weighting Functions
183 GHz Water Vapor Weighting Functions
Height (km)
12Option 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 lt 5 km
- Cons
- Reduced accuracy in clouds
- Reduced sensitivity to PD in moist conditions
- Uncertain with what accuracy this can be done
13Conclusions
- 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