Transcript Document 7601531

NASA High-Altitude Precipitation/Wind
Radars for Hurricane Research
Gerald Heymsfield
NASA/Goddard Space Flight Center
([email protected])
Lihua Li /University of Maryland Baltimore/GEST
James Carswell /Remote Sensing Solutions, Inc.
Outline:
• Current high-altitude radars for hurricane
research with NASA ER-2
• Future directions with tropospheric wind
measurements and surface winds from highaltitude aircraft and high-altitude long
endurance UAS (HALE).
GODDARD SPACE FLIGHT CENTER
Science Drivers
Targeted observations and real-time
information from hurricanes & other extreme
weather events in remote regions.
Tropospheric wind measurements with higher
spatial and temporal resolution than currently
available from lower altitude aircraft
HALE such as Global Hawk currently provide
long-duration (>24 hours), high-altitude (>18
km) capability.
More than a decade of high-altitude Doppler
wind measurements from ER-2 aircraft over
weather systems including tropical storms
GODDARD SPACE FLIGHT CENTER
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Current Hurricane Research Using
ER-2 Doppler Radar (EDOP)
X-band (9.6 GHz)
•Nadir pointing beam -> derive vertical motions
•Fixed forward pointing beam (30 degrees) for
derivation of along-track winds and cross-polarization
measurements.
•First flown 1995, developed early 1990’s.
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Cloud Radar System (CRS)
W-Band (94 GHz)
CRS (94 GHz)
EDOP (9.6 GHz)
-->Dual-frequency (X, W>CloudSat simulator
Band) provides information
>Strongly attenuated by
on hydrometeors
precipitation, large ice.
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Radar Wind Measurements
Motivating Factors for Conical Scan
Radar Wind Sensor (RAWS) (Moore
et al., 1992)
Spaceborne radar wind measurement
study (X- and Ka-band) with 30o,
35oconical scan funded by NASA to
complement Lidar Wind Sounder
(LAWS)
Imaging Wind and Rain Airborne
Profiler (IWRAP) (Esteban,
Carswell..2005)
P3-based C- and Ku-band, four incidence
angle, conical scanner flown in
hurricanes the past seveal years
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NASA Conical Scan Radars in
Development
High-Altitude Imaging Wind and Rain
Profiler (HIWRAP)
Ku, Ka-Band (14 and 35 GHz) radar funded by
NASA Instrument Incubator Program (IIP)
Aircraft: WB-57, Global Hawk
Completion of basic system: 15 months
UAV Radar (URAD)
X-Band (9.3, 9.4 GHz) funded IR&D Goddard
Space Flight Center
Aircraft: ER-2?, Global Hawk
Completion of basic system: 6 months
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NASA High-Altitude Aircraft and HUAS
WB-57
ER-2
Global Hawk
WB57
Not Yet Operational
70
631
Maximum
Duration (hrs)
8
51
Maximum
Payload (lbs)
2,900
Altitude (kft)
Max. Microwave
Aperture (ft) 2
2.5
6,000
4.2
60 to 65
30
2,000-3,000
4.3
1Improvements
in progress TBD
2Conical scan requires large opening
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URAD Measurement Concept
 Initial development: 2004 Atlantic
Seedlings and Hurricane
Experiment (ASHE) proposal
using Global Hawk to study TS
cyclogenesis off the coast of Africa
 Nadir capabilities of EDOP, plus a
second conical scanning beam to
provide estimates of horizontal
winds in cloud and the ocean
surface winds.
X-Band, separate nadir (9.4
GHz) and scanning radar
(9.3 GHz) subsystems, fully
scanable antenna up to 35
degree elevation.
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 Conical scan provides 3-D
surveillance of precipitation,
horizontal winds in precip. and
surface winds.
 Low cost solution using existing
radar technologies.
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URAD Configuration in Global
Hawk
URAD was designed for installation with minimal GH modifications
Interface for
Global Hawk
Two-axis positioner
to achieve conical
scan and elevation
adjustment.
Scanning and fixed
nadir antenna
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URAD Hardware
Nadir Magnetron Subsystem
TWT transmitter, high voltage power
supply and modulator
Two axis
positioner to
achieve elevation
and azimuth scan
Scanning Receiver hardware
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HIWRAP Development
Technology development
emphasis.
*3D winds (grid point
retrieval) and reflectivity
*Two frequencies and two
incidence angles to increase
the number independent
wind measurements
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Utilize low power solid-state
transmitter instead of high
power tube-based
transmitter - more suitable
for high-altitude and space
Develop single aperture
antenna for two beams and
two frequencies.
Develop high altitude, power
efficient real-time digital
receiver and processor
 GPM frequencies
HIWRAP Measurement Concept
Two look angles and two frequencies
Many independent radial wind
measurements within grid
volume are used to calculate
wind vector
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HIWRAP Measurement /Accuracy
Requirements
Parameter
Reflectivity
Doppler
Retrieval Products:
(resolution 1 km x 1
km x 60m)
Surface wind speed,
direction
Horiz. wind
speed/direction in
precip/cloud regions
Vertical Wind
Precipitation Rate
Range
0-60 dBZe
0-150 ms-1
Accuracy
1dB
<0.5 ms-1,
SNR=10
0-60 ms-1, 0360o
1.5 ms-1 or 10%
of magnitude,
15o
1.5 ms-1 or 10%
of magnitude,
15o
2 ms-1
1 mmh-1
0-100 ms-1, 0360o
-20 – 20 ms-1
0 – 100 mmh-1
Based on 10 W Ka-band and 30 W Ku-band power amplifiers
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HIWRAP in Global Hawk
Scanner, slip ring & fiber
optical rotary joint
Aircraft floor
Power amplifiers &
RF front end
Mounting frame
Radar RF/IF
Antenna reflector
Antenna feeds
Radome
HIWRAP was designed for installation in GH with minimal modifications
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WB-57 Test Flights
Planned Summer 2008
Radome for Kuand Ka-band
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WB-57 6-foot pallet
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Summary
Radar-based winds using conical scan from above
hurricanes and other extreme weather events is
promising approach for high-altitude aircraft,
HALE, and space.
HIWRAP hardware completion and flight testing
on WB-57 aircraft -> Summer 2008.
Completion of basic URAD system by Fall 2007
Migrate both radars to Global Hawk when one
becomes available.
Lidar-based wind instrument (TWiLiTE) due for
completion for WB-57 about same time as
HIWRAP---> opportunity to remotely measure
winds in precipitation-filled and clear regions.
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Tropospheric Wind Lidar Technology Experiment
(TWiLiTE) Instrument Incubator Program
• TWiLiTE will demonstrate, for
the first time, downward
looking wind profiles from 18
km to the surface obtained with
an airborne direct detection
scanning Doppler lidar
• Serves as a system level
demonstration and as a
technology testbed
Rotating
telescope
Doppler Receiver
• Leverages technology
investments from multiple
sources
• TWiLiTE is a collaboration of
government (NASA/NOAA),
university and industry partners
UV Laser
TWiLiTE system integrated on WB57 3 foot pallet
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Source: Bruce Gentry, NASA/GSFC
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