Airborne Phased Array Radar (APAR) – The Next Generation Airborne Polarimetric Doppler

radar

NCAR Earth Observing Laboratory APAR Team

(Wen-Chau Lee Presenting) 27 May 2015 [1]

Where are we now in Tropical Cyclone Forecast?

3 Sweep out 2 helical surfaces

Can synthesize 3-D wind field by flying by a phenomenon.

ELDORA in BAMEX, St. Louis, 2003 NRL P3 (2002-2012)

ELDORA was the only airborne radar that resolved convective scale weather phenomena.

NOAA P3

ELDORA Observations of Hurricane Rita (2005)

Eyewall Conceptual Model

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Vertical Structure of Rita (2005)

The unprecedented concentric eyewall structure in Hurricane Rita deduced from ELDORA observations was published in Science (Houze et al. 2007)

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1. Lower Atmospheric Observing Facilities Workshop: Meeting the Challenge of Climate System Sciences (Smith et al. 2013) 2. NSF Community Workshop on Radar Technologies (Bluestein et al. 2014).

• “A critical gap is that ELDORA (Electra Doppler Radar), which has been used by NSF-funded investigators to study mesoscale convective systems, fronts, other mesoscale phenomena and tropical cyclones, needs a new aircraft platform.”

• “Airborne radar systems are relatively expensive to develop, put in the field, and maintain, but are critical for observations from areas otherwise not accessible.”

• “…ELDORA-like airborne Doppler radars, …, polarimetric radars, …, are required to answer key current and emerging science questions.”

• “The emerging radar technologies that would be most helpful in answering the key scientific questions are: phased-array technology, which can improve temporal resolution without reducing data quality …”

Community Voices about APAR:

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• Hazardous Weather – Hurricane, Tornado and severe weather, Winter storms, Flash flood

• Weather/Climate Interface – Convection in tropics, MJO, Easterly waves

• Radiation and Global Energy Cycle - Particle type/size and radiative transfer

• Air Chemistry - Transport of aerosol, Water vapor and chemical species, Interaction of chemical species and cloud

• Polar Frontier (Arctic & Antarctic) - Mixed phased clouds, Chemistry, Energy balance

• Radar and NWP - Radar data assimilation, Model verification

Scientific Frontiers for Airborne Radars:

EOL Airborne Phased Array Radar (APAR)

• Seven-year development schedule • University and industry partnerships

key to successful design and build • Deployable on NSF/NCAR C-130

aircraft or similar platforms • 20+ year operational lifetime • APAR can be implemented in

operational storm measurements (e.g. flown on US Air Force C-130 Hurricane Hunters)

Antenna Radome

Antenna Array

Transmit/receive modules (T/R) modules

Backplane

•Electronically scanned (no moving parts) •4 Phased-array antennas on the aircraft •3-D Volume scanning from the aircraft •Operates at C-band (look deep into storms) •Dual polarization, high resolution

• Enabling focused scientific research in high-impact weather, cloud microphysics, storm dynamics, radiation and climate

• Compliment a suite of existing instruments on NSF/NCAR C-130

• Addresses specific objectives in NSF and NCAR Strategic Plans

• Data at spatial/temporal scales that match numerical models

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Surveillance radar.

APAR horizontal scans

Radar Beam Resolution Matters

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BAMEX Squall Line Observed by Three Wavelengths

X-band

S-band C-band

X-band

NOAA P3 LF

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APAR Improvement in along track scanning resolution

Comparison of ELDORA flat plate antenna 300m along-track fore/aft beam resolution (black dashed lines) and

C-130 APAR designed 150m Active Electronically Scanned Array (AESA) along track resolution (red dashed

lines)

Performance Comparison: Airborne Research Radars Parameter NOAA

G-IV TDR

NOAA P-3 TDR

ELDORA APAR

Frequency (GHz) 9.3 9.3 9.3 – 9.8 5.35 – 5.45

# Elements (El/Az) n/a n/a n/a 64/56

# Total elements per panel

n/a n/a n/a 3584

Beamwidth (El/Az) (degrees)

2.7 1.35/1.9 1.8/2.0 1.6/1.8

Antenna Gain (dB) 36.5 40 39 41

MDR @ 10 km (dBZ) -9 0 -11 -15

Peak Transmit Power (KW)

8 60 40 14.3

Polarization Linear Horizontal

Vertical Horizontal Dual Linear

Spatial Resolution @ 10 km (m)

471 314 314 314

Along track spacing (m)

1125 1500 300 130

Pulse width (µsec) .41 0.25-0.5 0.25 to 4.0 0.5 to 50

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APAR combines reflectivity, velocity and measurements. Attenuation at C-band

frequency is lower in heavy rain.

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APAR Proposed Scan strategy from C-130. Simultaneous 4 beam transmit strategy for 3-D volume generation

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Animation of APAR single forward angle as it appears coming from 3 of the 4 APAR array faces. Maximum radar range ~75km

depending on attenuation at C-band

APAR ARCHITECTURE

LRU (8x8 radiating elements)

Up/Down

Converter Digital

Transceiver Host

Computer

Array antenna Front-end

• Antenna radiators • Balanced feed • RF beamformer • Power dist. board • Data dist. Board • Array antenna

calibration

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TR modules

• 56 LRUs x 64 elements •Total= 3584 TR modules

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Radar Processor/Display

• Moments generation • Composite radar display • Real-time dual Doppler

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Array antenna front-end 1 Array TR-modules 2

Array antenna back-plane 3

Radar back-end 4

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Radar processor/display 5

Radar scheduler 6

Radar back-end

• UP/DOWN converter

• Digital Transceiver • Host Computer • Waveform design • Data processing

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LRU (8x8 radiating elements)

Array antenna backplane

• Data & Control (Master FPGA)

• Power, DC/DC converters • RF Power Div/Comb board • Array Formatter board

Array Formatter controller

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Radar Scheduler

• Scan scheduler/optimizer • Set PRF, Pulse width, gate spacing, etc.

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APAR Development Timeline Present Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7

Full size APAR airborne prototype (7x8 LRU’s)

Four APAR systems NSF/NCAR C-130

~¼ size PAR prototype (4X4 LRU’S)

Acceptance Test and Evaluation

Phase 1 Phase 2 Phase 3

LRU Development (64 elements)

Funding Increment Required

6.5M

SHORT TERM

LONGTERM • Brick T/R mod.

• COTS RF parts • GaAs • Cost: > $200/TR mod. • Bulky

• Tile T/R mod. • MCC is required • SiGe or GaAs • Cost: < $100/TR mod. • Compact, low mass

Project Management Protocols (e.g., PDR, CDR, Acceptance Test, etc.)

Scientific and Societal Impacts of APAR on Hurricane Research and Prediction

• The C-band APAR with dual-pol and dual-Doppler capabilities will revolutionize hurricane research and prediction from genesis to landfall

• APAR provide 3D inner core kinematic and microphysical structures, critical for improving hurricane track and intensity monitoring and prediction via assimilating airborne radar data into operational and research models

• The APAR design can be cloned for other C-130s (e.g., Air Force Hurricane Reconnaissance fleet, and C-130 fleet in other countries).

• Three to four C-130s with APAR can provide continuous and routine inner core structures that cannot be achieved by the two NOAA P3s with TDRs.

Hurricane Sandy Rainfall forecasts by PSU stream-1.5 real-time 3-km WRF ENKF run

Questions?

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Engineering and Science Expertise Antenna Aeronautical Signal Processing Industry (e.g. PCB, chip, etc.) Mechanical Tropical Cyclone Severe Weather (tornado, MCS) Polar Boundary Layer Winter Storms Climate Systems

APAR Advisory Panel Membership 2015

Dr. Bob Palmer, Center for Applied R&D, Univ. of Oklahoma (OU) Prof. V. Chandrasekar, College of Engineering, Colorado State Univ. (CSU) Prof. Stephen Frasier, College of Engineering, Univ. of Massachusetts (UMass) Prof. Dejan Filipovic, Dept. of Electrical, computer and Energy Engineering, Univ. of Colorado (CU) Mr. David Conway, Massachusetts Institute of Technology (MIT) Dr. Chris Davis, Advanced Studies Program (ASP) NCAR Prof. Robert A. Houze, Univ. of Washington (UW) Dr. Frank Marks Hurricane Research Division (HRD)/NOAA Dr. Scott Braun Goddard Space Flight Center (GSFC), NASA Prof. Alan Blythe, School of Earth and Environment, University of Leeds (UK)

APAR Advisory Panel (AAP) 19-20 March 2015

APAR LRU DEVELOPMENT Brick (Short Term) vs. TILE (Long term)

8 channel brick TR module

Radome

Aperture Board - Radiator board

8-Channels brick TR mod. - TR modules - Heat sink - RF beamformer (Azimuth)

Backplane - Data distribution board - RF beamformer (Elev.) - Power supplies - Vertical connectors

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TR Module Architecture Considerations

ATT H-Pol

V-Pol

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DUAL POL. (ATAR)

Rx

LNA

ATTTT

PS

ATT PS

ATT PS

LNA

PA

LNA

Rx-H

Rx-V

Tx-H/V

H-Pol

V-Pol

DUAL POL. (ATSR)

Fewer components : • cheaper • consumes less power • weighs less due to

reduced heat sink req’s.

Allows for simultaneous Co-pol and Cross-pol measurements

Tx