The Next Generation Polarimetric Airborne Doppler Radar Wen Chau Lee, James Moore, J. Vivekanandan, Eric Loew, J. Salazar Peisang Tsai, and Vanda Grubišić National Center for Atmospheric Research* Boulder, Colorado 80307 USA * National Center for Atmospheric Research is sponsored by the National Science Foundation. This work sponsored by NSF Grant M0904552
Background 1977 NOAA WP 3D makes first atmospheric measurement of Hurricane Anita using scanning, airborne radar. 1982 NOAA P 3 radar makes first Doppler derived wind measurement inside Hurricane Debby. 1993 NSF/NCAR s ELectra DOppler RAdar (ELDORA) is available to university researchers. ELDORA offers improved sensitivity, spatial and temporal resolution compared with NOAA tail Doppler radars. 2001 NSF/NCAR s Electra aircraft retired. 2002 ELDORA moved to NRL P3 587 January 2013 NRL P3 587 decommissioned. ELDORA is without an airborne platform. ELDORA in FASTEX, Shannon, Ireland, 1997 NSF/NCAR Electra (1992 2001) ELDORA in BAMEX, St. Louis, 2003 NRL P3 (2002 2012)
Anatomy of ELDORA ELDORA remains the only airborne radar that resolves convective scale structures Sweep out 2 helical surfaces Can synthesize 3 D wind field by flying by a phenomenon.
The unprecedented concentric eyewall structure in Hurricane Rita ELDORAby Observations of Hurricane (2005) deduced ELDORA data was published inrita Science (Houze et al. 2007)
Community Voices: 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. 2013). A critical gap is that ELDORA (Electra Doppler Radar), which has been used by NSFfunded 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 otherwise 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 EAC Brief December 2013 5
The Science Drivers (NSF Community Workshop on Radar Technologies, November 2012): Tropical cyclones Genesis, intensification, asymmetry, landfall, storm surge and inland flooding Tropical convection and climate processes Convection in MJO, easterly waves, oceanic convection Water cycle/cloud/microphysics QPE, particle size and radiative transfer, mixed phased clouds Severe storms Dynamics and structures, convection initiation, flash flood Chemistry Transport of aerosol, water vapor and chemical species Winter storms Frontal dynamics, heavy precipitation Radar and NWP Radar data assimilation, model verification Red: topics will benefit from dual pol capability
Objective Replace ELDORA with a radar that has the following characteristics: Compatible with existing NSF/NCAR aircraft and compliment a wealth of existing insitu and remote sensing instruments Better spatial and temporal resolution Improved sensitivity; reduced effects from attenuation Improved reliability Polarimetric measurements capability Revolution, not Evolution
Solution Airborne Phased Array Radar Active Electronically Scanned Array (AESA) technology on NSF/NCAR C 130 TOP VIEW SIDE VIEW
Engineering Considerations Radar performance must be carefully balanced with aircraft performance and size constraints Airborne radars on C 130, in general, have to consider the following factors: Aperture size limited to 1.5m x 1.9m Weight limited to 270 kg per aperture Prime power availability < 5.5 kva/aperture Cooling Aerodynamic
APAR Characteristics Parameter Units ELDORA APAR Frequency GHz 9.3 9.8 5.35 5.45 # Elements (El/Az) n/a 64/56 # Total elements per panel n/a 3584 Beamwidth (El/Az) Deg. 1.8/2.0 1.6/1.8 Antenna Gain db 39 41 MDR @ 10 km dbz 11 15 Peak transmit Power KW 40 14.3 Polarization Horizontal Dual Linear Spatial Resolution m 314 314 @ 10 km Along track spacing m 300 130 C band suffers less from attenuation than X band Design Goal: Meet or exceed ELDORA capabilities Exceeds ELDORA sensitivity Exceeds ELDORA capability Meets ELDORA spatial resolution Exceeds ELDORA along track resolution Pulse width µsec 0.25 to 4.0 0.5 to 50
APAR Architecture LRU (8x8 radiating elements) Array antenna Front end Antenna radiators Balanced feed RF beamformer Power dist. board Data dist. Board Array antenna calibration 1 Host Computer Digital Transceiver Up/Down Converter Radar back-end 4 UP/DOWN converter Digital Transceiver Host Computer Waveform design Data processing Array Formatter controller TR modules 56 LRUs x 64 elements Total= 3584 TR modules 2 1 2 3 4 Array antenna front end Array TR modules Array antenna back plane Radar back end Array antenna backplane Data & Control (Master FPGA) Power DC/DC (1+1) RF Power Div/Comb Master board Array Formatter board 3
The Brick T/R Module PCB by the numbers Board will be 5.9 by 8.5 (15 by 21.6 cm) 11 layers, 75/1000 thick 1300 components (~8 times the number used for the CASA radar T/R board) 3 different RF distribution networks integrated in the single PCB Each PCB generates ~20 watts of heat.
The FACE of APAR Single PAR Array 1.6m / 1.8m face area 4 PAR Arrays make up APAR System 8x7 Line Replaceable Units (LRUs) in each PAR 64 elements per/lru 3,584 elements / PAR 14,336 elements / APAR
Proposed APAR Development Schedule Phased Approach to Minimize Risks Present Year 1 Year 2 Year 3 Year 4 Year 5 LRU Development (64 elements) ~¼ size PAR prototype (4X4 LRUs) Full size APAR airborne prototype (7x8 LRU s) Four APAR systems NSF/NCAR C-130 Phase 1 Phase 2 Phase 3 Acceptance Test and Evaluation 14
Summary APAR White Paper submitted to NSF early 2014 LRU design and build underway using EOL internal funds to be completed Spring 2015 Issued RFI for T/R module design/development Seeking funding for Phase 1 Will form APAR Advisory Panel Will seek partners (university, government agencies, industry, and foreign)
Thank You
Scientific and Societal Impacts of APAR on Hurricane Research and Prediction The C band APAR with dual pol and dual Doppler capabilities will revolutionize future hurricane research and prediction from genesis to landfall The APAR design can be cloned for other C 130s (e.g., Air Force Hurricane Reconnaissance fleet) to provide routine and near continuous 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
Airborne Phased Array Radar Concept on NSF/NCAR C-130 Antenna Size: ~2.0 m X 1.5 m >3500 elements ~ 2 deg beam dual-pol ~200 m along track resolution NSF/NCAR C 130 Composite surveillance scans