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Assessing the Weather Observation Capabilities of a Spectrum Efficient
National Surveillance RadarMark E. Weber
NOAA OAR National Severe Storms Laboratory5 December 2017
5 December 2017 1
Fifteen Years of Meteorological Phased Array Radar (PAR) Research
5 December 2017 2
National Weather Radar Testbed
Storm Studies, Scanning Techniques
and Processing Algorithms
Forecasting Experiments
Technology Risk Reduction
Multifunction Phased Array Radar (MPAR) Concept
• Multiple stove‐piped radars• Rotating dish technology• Many nearing end‐of‐life
ARSR‐3 ARSR‐4ARSR‐1/2
ASR‐8 ASR‐9 ASR‐11
NEXRAD
Terminal Area
Long Range Aircraft
Long Range Weather
Weather
Current National Operational Radars
FPSMultifunction
Radar
Weather
Aircraft
Ground Based UAS Sense and Avoid
Non-Cooperative Target
Multifunction Phased Array Radar (MPAR)
• Has potential to lower cost by– Reducing number of radar units– Lowering O&M (no moving parts)– Streamlining support infrastructure– Simplifying training and logistics– Open systems procurement and
maintenance• Enhanced performance
TDWRAircraft
CARSR
5 December 2017 3
Radio Frequency Spectrum Implications
5 December 2017 4
Air‐Route Surveillance Radar (ARSR): 1.2‐1.4 GHz
Airport Surveillance Radar (ASR): 2.7‐2.9 GHz
Weather Service Radar(WSR‐88D): 2.7‐3.0 GHz
Terminal Doppler Weather Radar (TDWR): 5.5‐5.65 GHz
MPAR: 2.7‐3.0 GHz
Spectrum Efficient National Surveillance Radar (SENSR)
• “Spectrum Pipeline Plan” proposal– Participating agencies: FAA, NOAA, DoD, DHS– “Phase 1” approved by OMB and NTIA in January 2017
• Feasibility study for release of at least 30 MHz in the 1.30‐1.35 GHz band for non‐federal use– Accomplished by consolidating existing national operational surveillance radar networks
– Consistent with MPAR concept, but alternate approaches (“system‐of‐systems”) under evaluation
• Spectrum Pipeline Act mandates that auction occur by 2024
5 December 2017 5
SENSR Program Timeline (Unofficial)
5 December 2017 6
. . Phase 1 . . Feasibility Study
Research and DevelopmentPerformance Requirements
Concept of OperationsEngineering Analysis
Analysis of AlternativesMarket Survey & RFI
Establish JPO
. . . Phase 2 . . . . . .System Maturation
Industry ContractsDesign / Development
Fly‐off / Vendor Evaluations
. . . Phase 3 . . .
SolutionImplementation
Limited Production ContractTest / Evaluation
Prep for Spectrum Auction
Spectrum Auction Mature Requirements
2016 2017 2018 2019 2020 2021 2022 2023 2024
Spectrum Decision andSENSR Solution Implementation Contract Award
Pending SENSR Architecture Decisions
*Conway et al., 2015 7
Active Array Single Beam
Up/DnConv
TR Modules
Analog Beamformer
Digital Receiver/Exciter
Analog
Digital
Digital Subarray
Analog
Digital
Up/DnConv
Up/DnConv
Analog Overlapped Subarray Network
Digital Receiver/Exciter
Digital Beamformer
Beam Cluster
Analog
Digital
Up/DnConv
Up/DnConv
Digital Receiver/Exciter
Digital Beamformer
Full Beam Set
All‐Digital
Up/DnConv
5 December 2017
Antenna Configuration Level of Digitization
Cost*Single‐ or Multi‐Mission Radars
TR Modules
TR Modules
A/D A/D
A/D
A/D
A/D A/D
Preliminary SENSR Performance Requirements
• Five mission areas– Near‐/Short‐/Long‐range aircraft
surveillance (DoD, DHS, FAA)– “Air traffic control” weather (FAA, DoD)– “High resolution” weather (NOAA, FAA, DoD)
• High resolution weather requirements derived from WSR‐88D capabilities– Include goals for one minute volume scan
updates and flexible, adaptive scanning
• NOAA SENSR feasibility study goals– Assess/refine requirements and provide
justification– Demonstrate technical approaches to
meeting them
5 December 2017 8
Outline
• Introduction• NOAA Research Activities• SENSR Program Directions• Summary
95 December 2017
Framework and Synergies
Ten Panel Planar Array Demonstrator
Cylindrical Array
Demonstrator
Advanced Technology
Demonstrator
PolarimetricCalibration and Correction Technique Evaluation
Computational Electrodynamic
Modeling
Command and Control
Analysis and Simulation
Data Quality Analysis and Simulation
Data Assimilation and Warn on
Forecast Studies
KOUN Rapid Scan Dual‐Pol Data Collection and
Analysis
Radar NetworkAnalysis and Performance
Industry Studies
System Modeling
All‐Digital Array Architecture
Mission BenefitsCommand and Control andData Quality
Dual Polarization
Co/Cross Pol Error Models
Scan Strategy RequirementsDwell‐time
Requirements
Fundamental Research
29 August 2017 10Hardware Based Evaluation Numerical Simulation Data Analysis
Warn on Forecast Concept
• Use state‐of‐the‐art high resolution numerical weather prediction (NWP) models to warn public of severe weather threats– 1 km resolution, convection
resolving– ensembles to characterize
uncertainty• Continuously assimilate radar
and satellite data into model
5 December 2017 11
• Goal is to extend average tornado warning lead times to 40‐60 minutes
Truth
One
Minute Scan
s (PAR
)Five M
inute Scan
s (W
SR‐88D
)
Reflectivity (dBZ) Vertical Vel (m/s)
Analysis after 15 minutes of data assimilation
PAR Rapid Volume Scanning Benefit
5 December 2017 Figures from Yussouf and Stensrud, 2010
U (m
/s)
V (m
/s)
W(m
/s)
T (oC)
q (gm/kg)
12
Forecast Time (0‐50 min)
Forecast Errors for Following 50 Minutes
Enhanced Low Altitude Coverage Benefit
5 December 2017 Cho, J., “Revised MPAR Network Siting Analysis”, MIT Lincoln Laboratory ATC‐425, 2015 13
All Urban
Aircraft 29 84
Weather 15 49
All Urban
Aircraft 30 89
Weather 30 90
WSR‐88D coverageat 1000’ AGL
Legacy Networks Percent Coverage
MPAR coverageat 1000’ AGL
MPAR Network Percent Coverage
Planned Studies
• Warning enhancement benefits for high impact phenomena– Tornadoes, large hail, damaging wind– Flash flooding– Downbursts, convective turbulence, small hail
• Benefits of assimilation of rapid‐scan dual‐polarization observations
• Sensitivity of benefits to PAR data quality differences
5 December 2017
NSSL Experimental WSR‐88D (KOUN)
Phased Array Radar Testbed
14
WSR‐88D Volume Coverage Pattern (VCP) 12
5 December 2017 15
Elevation Angle (°)
Number of Tilts
CPI DescriptionMean Scan Time per Tilt (s)
0.5 – 1.3 3
Long PRT scan for range‐unambiguous surveillance
Short PRT scan for Doppler velocity30.8
1.8 – 6.4 6 Interleaved long PRT surveillance and short
PRT Doppler pulses12.8
8.0 – 19.5 5 Short PRT for Doppler and reflectivity 12.0
24.5 – 60.0 8 Short PRT for Doppler and reflectivity 8.0
Totals 22 293.2
PAR Rapid Weather Scanning Concepts
1Yu et al. (2007); 2Torres et al. (2013); 3Weber et al. (2017); 4Melnikov et al. (2015) 16
Widened Transmit Beam Multiple Receive Beams
Tx 1Tx 2
Tx 3
Receive
Beam Multiplexing1Adaptive Weather Scanning2
Receive Beam Clusters3 Multi‐beam Technique4
Time
5 December 2017
Angle1
Angle 2
Time
Angle 3
Angle 4
Data Quality Simulator
17
WWSR
WSR‐88D Base Data(Level II)
Data Conditioning
Spatial Sub‐sampling
Scattering Center
Simulation
Radar Sampling
WWSR
Simulated Time Series
Data
Digital Signal Processing
Simulated PAR
Base Data
PAR Parameters
5 December 2017
• Antenna Patterns• Co/Cross Polar• Transmit/Receive
• Range Sidelobe Patterns• CPI Structure• Single‐Pulse Sensitivity• Range‐Gate Spacing
• Pulse Phase Coding• Simultaneous or Alternate
H/V Transmit• Antenna Rotation• Volume Coverage Pattern• Split‐Cut Scans
Torres, Boettcher, Curtis, Nai and Schvartzman, IEEE Radar Conference 2018
Simulation of Angle‐SidelobeImpacts
5 December 2017 Torres, Boettcher, Curtis, Nai and Schvartzman, IEEE Radar Conference 2018 18
Input Data
Simulation‐64 dB min sidelobes
Simulation‐47 dB min sidelobes
Dual‐Polarization Basics
Polarimetric radar variables are sensitive to hydrometeor (1) size, (2) shape, (3) orientation, (4) density, and (5) water content
Differential reflectivity Zdr = Zh/Zv
Shape
Orientation
Phase composition
Zv Zh 1drZ
1drZ
icewater ( ) ( )water icedr drZ Z
5 December 2017 19
Phased Array Radar “Geometric Bias”
5 December 2017 20
Copolar (H)Relative Gain (dB)
Crosspolar (V)Relative Gain (dB)
60o
‐15o
0o
0o‐45o 45o0o‐45o 45o0o
Azimuth Angle (φ)
Elevation An
gle (θ)
ZDR Bias (dB)0
‐10
‐20
‐30
5
0
‐5
Polarization Patterns for Horizontal (H) Dipole Radiating Element
30o
F(φ,θ) = Felement(φ,θ) x Farray(φ,θ)
‐45o
0
‐5
‐1045o
Impact of Antenna Architecture
21
Reflector Antenna
• Well‐aligned H/V patterns
• H/V orthogonal at all scan angles
• Cross‐Pol independent of scan angle
Single Face Rotating PAR
• H/V patterns vary with elevation scan angle
• H/V orthogonal at all elevation scan angles
• Cross‐Pol independent of elevation scan angle
Cylindrical PAR
• H/V patterns vary with elevation scan angle
• H/V orthogonal at all elevation scan angles
• Cross‐Pol independent of elevation scan angle
Multi‐Face Planar PAR
• H/V patterns vary with az/el scan angle
• H/V are non‐orthogonal off principal plane
• Cross‐Pol dependent on scan angle
5 December 2017
Increasing Scan Flexibility, Increasing Dual‐Polarization Measurement Challenges
Calibration, Alignment and Bias Correction Research
• Dual polarization antenna element characterization• Cylindrical array benefits and challenges• In situ calibration and alignment techniques
– Near‐ and far‐field probes– Mutual‐coupling
• Small UAS far‐field calibration probe development• Computational electrodynamic modeling (CEM) correction approaches
• Waveforms and processing techniques that mitigate dual‐pol variable biases
5 December 2017 22
Polarimetric Calibration Research Infrastructure
23
Far‐Field RangeNear‐Field Range
Dual‐Pol Planar Array Demonstrator (1.6 m2 )
Dual‐Pol Cylindrical Array Demonstrator (1.4 m2)
Advanced Technology Demonstrator (12.2 m2)
Small UAS Calibration Probe
5 December 2017
Outline
• Introduction• NOAA Research Activities• SENSR Program Directions• Summary
245 December 2017
Status
• SENSR Joint‐Agency Program Office (JPO) established
• Industry responses to initial SENSR “Request for Information” have been received and evaluated
• Government review of requirements underway:– Scope– Technical risk– Mission impact
• Expanded interaction with industry planned during “Phase II”
255 December 2017
Importance
• SENSR likely to be the largest radar procurement in history– Aggregate aperture of radars it will replace is ~15,000 m2
• Offers unique opportunity to modernize national surveillance radar networks using funding from spectrum auction proceeds
• Significant potential mission benefits for NOAA/NWS– PAR rapid scanning supports enhanced severe weather warning
– SENSR network configuration may improve coverage at low altitude
265 December 2017
Challenges Imposed by Compressed Acquisition Timeline
• Validating technical requirements appropriate for PAR• Quantifying mission impacts of changes to legacy
capabilities• Assessing risks in achieving key performance
parameters (e.g. dual‐polarization variable estimate accuracies)– Can shortfalls be addressed through future planned product improvements?
• Reducing PAR costs well below those of current DoD systems
275 December 2017
Summary
• Multi‐agency SENSR feasibility study underway
• NOAA’s research program addresses SENSR weather observation requirements, mission benefits and relevant technologies
• Significant NOAA mission benefits possible, but aggressive timeline and evolving multiagency requirements pose challenges
285 December 2017