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transcript
Usage and Protection of the Earth Exploration Satellite Service
J. Piepmeier
NASA Goddard Space Flight Center
Microwave Instrument Technology Branch
Greenbelt, Maryland USA
COSPAR Scientific AssemblyMontréalJuly 14, 2008
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Earth Exploration Satellite Service
• Since 1972, spaceborne microwave radiometers have provided all-weather day-night observations of our planet
• Over 25 environmental variables are estimated from microwave data• Data used in operational and research weather prediction, climatology
research and monitoring, and environmental observation.• NASA’s Earth Observing System covers 6.9 GHz – 2.5 THz
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JAXA’s AMSR-E on NASA’s EOS Aqua
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6.9, 10.7, 18.7, 23.4, 36.5, 89 GHz
Oceanographic Data Products
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1998 Hurricane Bonnie
Sea Surface Temperature
From TRMMMicrowaveImager
http://earthobservatory.nasa.gov/Newsroom/NewImages/Images/trmm_sst.jpg
1998 Hurricane Danielle
Aircraft sortie
Danielle Microwave Imagery (10.7 – 325 GHz)
X K wv
Ka W
Imaged from NASA’s DC-8 and ER-2 on August 30, 1998
Air Temperature Decadal Trend
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Decadal trends (1979-2007) in Microwave Sounding Unit channel for Lower Troposphere (~<5km) Temperature (oC).
Data poleward of 82.5° North and 70° South, as well as areas with land or ice elevations above 3000 meters, are not available and are shown in white.
Frequencies for Observing over Ocean
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Frequencies for Observing over Land
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RFI Index: TB6H - TB10H
Global Radio Frequency Interference (RFI)
RFI contamination occurs at both 6.9 GHz (widespread in U.S., Middle East, Asia) and 10.7 GHz (mainly in England, Italy, Japan)
MicroRad-2004 - Rome, Italy Ashcroft/Li/Njoku/WentzCourtesy: E. Njoku, JPL
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RFI in Spaceborne Radiometers
Frequency Band
Confirmed or Potential
Instruments Nature of RFI
L-band Potential SMOS/MIRASAquarius/SAC-D, SMAP
Likely to be OOB emissions from terrestrial radars
C-band Confirmed
Expected
SMMR on SeaSat and Nimbus 7 AMSR-E on EOS AquaWindSat on Coriolis MIS on NPOESS
Majority is likely fixed service (FS) communcations. Mobile service (MS) and radiolocation possible. Proliferation of Part 15 UWB devices expected.
X-band Confirmed Potential
AMSR-E, WindSat GMI on GPM core satellite MIS
Allocation shared with FS. WindSat uses extended band up into Direct Broadcast Service (DBS).
K-band 24 GHz Potential MIS and GMIATMS on NPP (and NPOESS)
Allocation shared with Fixed Satellite Service (FSS) S-E links and FS. No confirmed cases. Shared with UWB vehicular radars. No RFI experienced.
Ka-Band Potential MIS and GMI Allocation shared with FS and MS. No confirmed cases.
V-band Potential ATMS PATH from NRC Decadal Survey
Part-15 devices growth explosion expected. Allocation shared with inter-satellite service links visible from GEO.
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Engineering Approach – SOE
• Survivability: avoid damage from RFI• Operability
– Measure without error in the presence of interference– Receiver selectivity
• Excisability– Receive interference but can remove it– Detection and excision
• Spectral (sub-banding)
• Temporal (pulse blanking)
• Statistical or amplitude (kurtosis)
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Spectrum Allocation
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Terrestrial Long-Range Radars
• Operate in radio-location service• Highest power with widest
spectrum• List of U.S. L-band radars used
– Aerostat (L-88): 12 radars– AN/FPS-108: 1 radar– AN/FPS-117: 31 radars– AN/FPS-124: 39 radars– ARSR-1: 23 radars– ARSR-2: 17 radars– ARSR-3: 14 radars– ARSR-4: 42 radars
• Multiple military (Army, Navy, USMC) radars not included– No technical data available on most– No location data available on all
(mobile)
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AN/FPS-108 COBRA DANE
worst case = 1 W at Aquarius ~ 1012 K
MUST LIMIT POWER
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Frequency Analysis for Operability
• How much selectivity is enough?
• Use worst offender – AN/FPS-117 within U.S.– 25 kW peak (4 kW average)
transmitter– 39 dBi gain antenna– 1383 MHz maximum frequency in
NTIA filings
• Frequency Dependent Rejection method– Transmitter spectrum– Receiver bandpass response– Rejection based on frequency
offset
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AQUARIUS FPS-117 FDR - 25 MHz BW 7-Pole, 9-Pole & Brick Wall Filter Comparison
1385 MHz
1400 MHz
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Filtering is not enough!
Aquarius West Coast PathStart: Lat=-125, Lon=-3 deg
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AQUARIUS Radiometer
Radars start to be
visible
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0.1 K0.01 K0.001 K
AQUARIUS Radiometer
• Detect pulses• 3 x Nyquist sampling of
radar azimuth beam
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0.1 K
0.01 K
0.001 K
10 ms
-240 -220 -200 -180 -16010
-5
10-4
10-3
10-2
10-1
100
CC
DF
P int (dBW)
Real Life Aquarius RFI in Ground Experiment
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0 200 400 600 800 1000 1200-20
0
20
40
60
80
time (s)
T
B
0 200 400 600 800 1000 1200-2
-1
0
1
2
3
time (s)
T
B
10-ms integration
2.88-s integration
Prediction is 1000X worse over land!
100 K10 K1 K0.1 K0.01 K
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L-band Interference Suppressing Radiometer
256K FIFO10-bit A/D’s
Digital filters/ APB/FFT/Integrator
Threshold
NBLANK
NWAIT
NSEP
Real-time removal of pulsed interference
APB off APB on
• Two 200 MSPS, 10 bit ADC’s: can sample either a 100 MHz channel or 2 pols at 50 MHz each, real-time “asynchronous pulse blanking” (APB) algorithm
• Su 05 Canton campaign results
Courtesy: J. Johnson, Ohio State
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Agile Digital Detector - University of Michigan
ADD Specifications and Performance• Direct sampling digitizer of V-pol and H-pol 1413 MHz
radiometer RF signals (no LO required)• Flight qualified FPGA processor
– <V*H> complex correlator forms 3rd and 4th Stokes TBs– 2nd moment provides fully polarimetric TB– 2nd and 4th central moment provides kurtosis– 16 frequency subbands over full 24 MHz radiometer passband
permits frequency domain RFI mitigation– Nyquist+ oversampling (x600) permits time domain RFI
mitigation
Aircraft prototype ADD and automated C&DH for scientific demonstrations in a relevant environment
Flight line for Texas WB-57 demonstration flight
Images of TB (left) and kurtosis (right) at Galveston coastal crossing during demo flight. Kurtosis responds only to non-thermal signals.
ADD spaceflight prototype brassboard. Analog signal RF and clock inputs at right.
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Soil Moisture-Active/Passive
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NASA’s first Decadal Survey MissionLaunched scheduled for 2013
L-band microwave radiometer and SAR
Regulatory Approach - EESS
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RAS Regulatory Framework
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EESS and RAS - Common Organizations
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Closing Thoughts
• EESS and RAS have differences (up vs. down, global vs. local)
• EESS and RAS have similarities (broad spectrum usage, need for spectrum outside of allocations)
• Collaboration possibilities exist– Spectrum surveys– EESS must put RAS technologies into space– WRC-11 agenda item for f>275 GHz
• Solution space– Regulatory– Technological
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