Results indicate successful performance of beam forming radiometer. Successful implementation of real-time calibration with emitted and injected Gaussian noise. Opportunities for improvement

Al-Hamdan, M.

Crosson, W.

Laymon, C.

Limaye, A.

McCracken, J.

Meyer, P.

Richeson, J.

Sims, W.

Srinivasan, K.

Varnevas, K.

NASA Technical Reports Server

MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 1
National Aeronautics and Space Administration
SCIENCE & MISSION SYSTEMS
MAPIR: An Airborne Polarimetric Imaging Radiometer
in Support of Hydrologic Satellite Observations
C. Laymon1, M. Al-Hamdan2, W. Crosson2, A. Limaye2, J. McCracken1, 
P. Meyer1, J. Richeson3, W. Sims1, K. Srinivasan2, K. Varnevas1
1George C. Marshall Space Flight Center, NASA, Huntsville, Alabama
2Universities Space Research Association, Huntsville, Alabama
3Integrated Concepts & Research Corporation, Huntsville, Alabama
https://ntrs.nasa.gov/search.jsp?R=20100033283 2019-08-30T11:41:01+00:00Z
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 2
Science Motivation
Earth Science
Vision 2030
March 2004
NASA Science Plan
2007
National Research Council
Earth Science and 
Applications from Space
January 2007
Reports contain common theme of need for 
measurements of precipitation, soil moisture, 
and sea ice and provide measurement goals.
SMAP
Soil Moisture Active Passive
2014-
Shortage of available airborne simulators and 
instruments to produce data for algorithm development, 
validation, and for applied science activities.
SWOT
Surface Water 
Ocean Topography
2020-
GPM
Global Precipitation Mission
2013-
ICESat-2
2015-
DESDynI
Deformation, Ecosystem 
Structure, Dynamics of Ice
2017-
N
A
SA
 E
ar
th
 S
ci
en
ce
 T
ec
hn
ol
og
y 
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ic
e
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 3
Science Applications
Irrigation  Scheduling
Agricultural Productivity
L-band RFI
Surveillance
Flood Water
Monitoring
Hydrologic
Modeling
National Defense
Applications
Weather
Forecasting
Supported NASA Missions:
SMAP
DESDynI
HyspIRI
NPOESS
GPM
Human Health &
Air Quality
Precipitation
Validation
Drought 
Detection
Landslides
Biomass & 
Ecosystem Health
L-band 
Instrument
Performance
Capabilities
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 4
System Architecture
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 5
Phased Array Antenna
The f ront side comprises 
passive antenna 
elements.
Behind the antenna 
elements are the 
electronic control 
components.
Each antenna 
element has a circuit 
board  that  steers 
the beam and 
switches RF 
polarization.
Frequency L- band (2 passbands)
Antenna Type Real aperture planar phased array
Array 81 element (9x9) electronic beam steering
Dimensions 102 x 102 x 18 cm
Weight 57 kg
Beamwidth 15 deg  (3dB at nadir)
Polarizations Horizontal, Vertical
Beams 2 simultaneous acquisition
Scan Type Push-broom, Conical, Staring at any angle
Control In-flight reprogrammable scan mode
Electronics Programmable Integrated circuit (PIC)
Calibration Emitted Gaussian noise source, 
50 ohm termination
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 6
Receivers
Four receivers acquire data at 
two narrow bands and two wide 
bands simultaneously.
The wide band receivers developed in-
house observe a wider spectrum for 
possible RFI that may ef fect observations.
All four receivers are integrated into 
a common enclosure with required 
splitters, f ilters and amplif iers.
shown
Theses radiometers are a byproduct of a 
Phase I and Phase II SBIR
Type Hach
No. Channels 4
Array 81 element (9x9) electronic beam steering
Narrow Wide
No. Receivers 2 2
Antenna Inputs 2 ea. 2 ea.
Passbands 1401-1425 MHz 1350-1450 MHz
Integration Time 10 ms (min.) 10 ms (min.)
Dimensions 7.6 x 7.6 x 7.6 cm 8.9 x 8.9 x 5 cm
Internal Cal. Loads Warm: 300 K
Cold: 210 K
Warm: 300 K
Cold: 210 K
Down Convert Freq. 8-32 MHz 10-110 MHz
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 7
Correlator & Digital Back End
Developed by Univ. of Michigan, 
Space Physics Research Lab
Correlator Module: 
Nallatech BenADC-V4 
firmware with Xilinx Spartan 
FPGA
Control Computer: 
RTD PC/104-Plus Stack
Dimensions 48 cm x  69 cm x  22 cm
Filters 16 subbands for each channel
Subchannel
Bandwidth
1.625 MHz (narrowband receiver)
7.8125 MHz (wideband receiver)
Clock 125 MHz oscillator
Digitizer 12 bit ADC; internal processing to 7 bit
Correlator Nallatech BenADC-V4 with Xilinx FPGA
RFI Processing ADD method: Computes I & Q moments
Control RTD PC/104-Plus stack
Storage 11 Mb packets
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 8
Command and Control
Key
Platform Altitude & Speed
No. Beams & Scan Angles
Maximum Allowable 
Integration Time
DBE Clock Speed
Minimum Allowable 
Integration Time Operational 
Integration 
Time
Antenna Switch Time
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 9
Calibration Method
Motivation: In-flight real-time continuous calibration
• Two diode calibration
• End-to-end calibration for a phased array system
• Calibrate every scan angle in real time
• Utilize mutual coupling between antenna elements 
as a calibration source
Implementation:
• Radiate a noise source from the center element of 
the array
• Radiated diode (ENR = 40 dB) and an injected 
noise source (~300 K)
Features:
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 10
Calibration
Antenna Gain = 3
(1) Two radiometer loads – Goodberlet et al, 2006
(2) Two Diode method
Receiver Noise Temperature 400 K
Pre-detection Bandwidth 24 MHz
Antenna Noise Temperature 300 K
Total Dwell Time 1 sec
Radiometer Warm Load (1) 300K
Radiometer Cold Load (1) 210K
Antenna Injected Load (2) 300K
Antenna Radiated Diode(2) 300K
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 11
Performance Evaluation
• TB time series, 10 azimuth angles
• shows system stability relative to range 
of Earth observations
• RMSE at 10 msec = 2.5 K
• no system-generated RFI observed
Observations sorted by angle along 
with diode measurements
• TB observations sorted by angle
• larger variability at 60°, and 160° can be 
attributed to lack of separation of scene 
obs from either or both calibration 
diodes
Experimental Set-up
• NASA EMI chamber
• Antenna on table looking at ceiling
• Scanning forward half only (0-160° azimuth) 
in 20° increments at 40° look angle
• Control system in adjoining room
10080 16014012010 20 40 600
10080 16014012010 20 40 600
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 12
Performance Evaluation
Evaluation: Results:
Beam patterns Symmetric
3 dB nadir beamwidth 15 degrees
Side lobe characterization 1st side lobe: -20 dB
Functionality of scan modes Functionality of all modes confirmed
Cross polarization isolation 30 dB
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 13
NASA P3-B Orion UTSI Piper Navajo, PA-31
Adapter box provides interface between antenna and aircraft
Single GN2 tank installed in left wing locker
Belly pod fairings fabricated in-house at UTSI
Forklift raises antenna into bomb bay
Structural interface for antenna inside bomb bay
Aircraft Integration
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 14
Piper Navajo PA-31 (N11UT)
Airborne Platform Configuration
Instrumentation
Supporting Equipment
• MAPIR
L-band brightness temperature
• Infrared Pyrometer
Surface temperature
• Laser Altimeter
Precise platform altitude
Vegetation canopy height
• PAR (Up, Down)
Photosynthetically active radiation
• Total Solar Radiation Pyrometer 
Downwelling solar radiation
• GPS Antenna
Platform position and attitude
• Nitrogen Source Tank with Electronic Controller
Humidity control inside MAPIR antenna enclosure
• Forward and Nadir Digital Video
• Data Acquisition System
PAR (Down)
PAR (Up)
SP Lite (Up)
Nadir TIR
IR Pyrometer (Down)
Laser Altimeter (Down)
GPS Antenna
Nadir Digital Video
Forward Digital
Video
MAPIR
PAR (Down)MAPIR
PAR (Up)
Laser Altimeter
IR Pyrometer
GPS Antenna
Nadir TIR
Forward Digital Video
Nitrogen Purge Tank
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 15
Flight Mission Profile
Crossville
CHESS
Tullahoma, TN
Watts Bar 
Reservoir
Normandy 
Lake
Study area in central Tennessee
Normandy Lake used for 
water calibration Four flight lines intersect over 
instrument station
CHESS tower at Oak 
Ridge National Lab 
Typical Climate 
Reference Network 
station configuration 
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 16
Vertical polarization; conical 
scan mode at 5500 ft. msl
Demonstrated Performance
Watts Bar 
Reservoir
Vertical polarization; 
Nadir at 3540 ft. msl
Vertical polarization; single beam conical 
scan at 40° look angle; 4600 ft.AGL; raw 
observed TB data, not gridded
CRN Station
at Crossville
Landscape is gently rolling 
with a mix of woodland, 
pasture and cropland 
283 270 260
265
236
200
220
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 17
RF Interference Characterization
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Subband
%
%
%
625 m AGL
533 m AGL
442 m AGL
No. of Subband
with RFI Detected
Horizontal Polarization
Vertical Polarization
625 m AGL
MSFC SCIENCE & MISSION SYSTEMS
IEEE Geoscience and Remote Sensing Symposium, July 26-30, 2010, Honolulu, Hawaii 18
Conclusions & Future Work
Conclusions
Future Work
• Results indicate successful performance of beam forming radiometer
• Successful implementation of real-time calibration with emitted and 
injected Gaussian noise
• Opportunities for improvement
• Improve calibration method
• Implement angle (phase) specific calibration
• Refine gridded product production
• Conduct additional performance tests
• In situ observations
• Mapping
• Instrument intercomparisons
• Conduct more RFI analysis
FR2.L07.2 (10:45, Nautilus)  Phased array radiometer calibration using a radiated noise source; 
Srinivasan, Limaye, Laymon, and Meyer


MAPIR: An Airborne Polarimetric Imaging Radiometer in Support of Hydrologic Satellite Observations

MAPIR: An Airborne Polarimetric Imaging Radiometer in Support of Hydrologic Satellite Observations

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