development of microwaveof microwave brightness temperature … · rdi tadiometers mhz, 60 mhz, ....
TRANSCRIPT
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DevelopmentDevelopment Brightness Tempe
t Nat N
Dave Walker, Jim RanDazhen Gu, Katie MacR
ElectromagneNIST-B
NOAA/NESDIS Workshopfrom Satellite Microwave
of Microwaveof Microwave erature Standards
NISTNIST
da, Chriss Grosvenor, Reynolds, Amanda Cox,
etics DivisionBoulder
Electromagnetics Divisionp on Climate Data Records e Radiometry, 22 Mar 10
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OUT
Hi t d B k d• History and Background• Previous Activities
C t A ti iti• Current Activities– Standard Radiome
F• Free space r• Identifying an
St d d T t– Standard Target • Target chara• Materials me
• Additional Capabilitiesp
LINE
dd
eterdi t i tadiometric measurements
nd quantifying error sources
cterizationeasurements
Electromagnetics Division
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Traceability—FoundMMeasur
Property of the result of value of a standard wherstated references, usuallyinternational standards tinternational standards, tchain of comparisons all
t i tiuncertainties
(
dation for Accurate trements
a measurement or the reby it can be related to yy national or through an unbrokenthrough an unbroken having stated
Based on the SI International System of Units)
Electromagnetics Division3
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NIST N i RNIST Noise R
• Coaxial radiometers: 301 – 18 GHz• N.B. Coaxial primary stdp y
• Waveguide radiometers18 – 26 5 26 5 – 40 3318 26.5, 26.5 40, 33• Each waveguide radiom
reflectometer & heterodreflectometer & heterod
R di tRadiometers
0 MHz, 60 MHz,
d. only up to 12.4 GHzy ps: 12.4 GHz – 18 GHz, 3 – 50 50 – 65 GHz3 50, 50 65 GHz.
meter contains a full 6-port yne receiveryne receiver
Electromagnetics Division
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Electromagnetics Division
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Thermal Noise Pr• Ambient & cryogenic (liqAmbient & cryogenic (liq
standards.
uTCry ≈ 0.65
◄Coaxial
Waveguide►
uTAmb ≈ 0.1
rimary Standardsquid nitrogen)quid nitrogen)
5 K
K
Electromagnetics Division
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HistHistProgram to support micginitiated in 2001
− Arose out of historArose out of historNoise Project with
− Program ran until 2og a a u tlack of funding
Current program resurrCurrent program resurr− Funded through C
Change InitiativeChange Initiative− Essentially picked
torytorycrowave remote sensing g
rical Microwave Thermalrical Microwave Thermal 30+ years’ experience2005, then canceled due to 005, t e ca ce ed due to
rected in June 2009rected in June 2009Congressional Climate
up where we left off
Electromagnetics Division
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PreviousPrevious
Concept for brightness te• Concept for brightness te• Standard Radiometer• Standard Target
Antenna Pattern Charact• Antenna Pattern Charact• Target Characterization
• Absorber meas. in WR
Reflectivity measurem• Reflectivity measurem
• Infrared imaging
ActivitiesActivities
emperature standardemperature standard
terizationterization
R-90 (8-12.4 GHz) waveguide
mentsments
Electromagnetics Division
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Previous ActivPrevious Activ
N bi t i TNear-ambient noise T mRadiometer free space pModeling of target proxD t t li itDetector nonlinearityStandard Terminology gyMeasurement of noise for Aquarius instrumentfor Aquarius instrument
vities (cont'd)vities (cont d)
tmeasurementsmeasurements
ximity effects
Projectjdiode calibration sources tt
Electromagnetics Division
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Microwave Remote
Important question: w
TargetBrightness
T t
Anpa
PhysicalTemperature
TemperatureIncident
BrightnesTemperatuTemperatu
Cal Target
Want as much as posComplications:p– conditions & environme– absolute vs relative “ac– absolute vs. relative ac
e-Sensing Metrology
hat quantity is traceable?
IF
ntennaattern
Internal V’sor P’s
ReceiverIF,
Processing,etc.ss
ureNoise Temp,
Li iure Linearity
sible included.
entccuracy” (uncertainty)
Electromagnetics Division
ccuracy (uncertainty)
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Brightness TBrightness TemperatuFramework for standardFramework for standard
C T η=
Rad.
Cryo
Amb
MinAT , η=
∫Std.Ant.
TA, out
0TB= TA, in
∫
∫=
π
η
4
maiM
outA TT , α=
Temperatureure:d radiometersd radiometers
TT )1( η+ SLMML TT )1( η−+
Ωφθ )( dF),(),(∫
mainnB dFT
TΩφθφθ
Ωφθ
Ωφθ
),(
),(
dF
dF
n
inn
)()(
),(
∫
∫=
mainn
mainML
dFT
dFT
Ωφθφθ
Ωφθ
.),(
),(),(
∫
∫=
othern
othernB
SLdF
dFTT
Ωφθ
Ωφθφθ
ainA TT )1(, α−+
Electromagnetics Division
L/1≈α
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UncertaintiesMLT
Ta : ∼ 0.2 KTA, out : ∼ 0.3 – 0.5 K,α : ∼ 0.5 %ηM : ??
If uη ~ uα , then at 20 GHz the 0.3 K – 0.8 K for TB between 2
So plan to develop stanSo, plan to develop stan18 – 26 GHz, 26.5 – 4
( )aoutAaL TTT −+= ,1 ( )aout
Ma ,αη
uncertainty in is 200 K & 300 K.
MLT
ndard radio-meters forndard radio meters for 40 GHz, & 50 – 65 GHz.
Electromagnetics Division
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Millimeter Wave Pla
Frequency Range - 1 to 75 GHzcurrently expanding to 110 GHz
(Could be up graded to 220+ GHz
Typical Uncertainties:
(Could be up graded to 220+ GHzUsing NIST probe position errorcorrection software and RF Equipment)
yp
1 - 26 GHzgain ± 0.20 dBpatterns ± 0.05 dB/dB to -40 dB
26 - 50 GHzgain ± 0.25 dBpatterns ± 0.07 dB/dB to -40 dB
50 75 GHz50 - 75 GHzgain ± 0.30 dBpatterns ± 0.10 dB/dB to -40 dB
nar Near-field Rangeg
Electromagnetics Division
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WR-42 StandaWR-42 Standa
Measured antenna patteMeasured antenna pattehorn (SGH) on the ne
rd gain hornrd gain horn
ern for a standard gainern for a standard-gain ar-field range.
Electromagnetics Division
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Electromagnetics Division
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Target reflecg
0.2
0.15
|
0 05
0.1|ΔΓ
0
0.05
ctivity effectsy
AIMR AntennaAIMR target, with cover
34 - 35 cm, 37 GHz
0 1 2 3 4 5 6 7 8 9 10Cart Position (mm)
Electromagnetics Division
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IR Thermal ImIR Thermal Immage of Targetmage of Target
Electromagnetics Division
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Noise Temperature Mea
Don’t normally measure neCheck of uncertainty near
Designed & built variable soDesigned & built variable sotemperature.
Measured it.
Tests entire system(except antenna)(e cept a te a)
asurements Near Ambient
ear ambient.ambient:ource with known noiseource with known noise
Electromagnetics Division
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0.02
0.015Typical Type BWR-42 System
unce
rtain
ty
0.01
Frac
tiona
l u
0.005
0 1000 2000
0
0 1000 2000
B Uncertaintym, 20 GHz
3000 4000 5000
Electromagnetics Division
3000 4000 5000T(K)
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Noise measurem
0.8
1
NFRad (Coaxial Radi
0.4
0.6
K)
8 GHz
0
0.2
.
Pred
icte
d (K
0 4
-0.2
0
Mea
sure
d - P
0 8
-0.6
-0.4M
260 270 280 290
-1
-0.8
60 70 80 90T
ents near ambient
iometer)
300 310 320 330
Electromagnetics Division
300 3 0 3 0 330T(K)
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Radiometric TargRadiometric Targ--Use existing NIST radionoise standards:
CryC
CryCryC
Rad. Am
C
aRad. AmAm
C
a
StdA t
a
x
0StdA t
a
x
0
NIST Noise Radiometer + Characte
Antx Antx
get Measurementget Measurementometer linked to primary
yoyoyo
mbmbmb
.t
Target.t
TargetTarget
erized Antenna
t.t.
Electromagnetics Division
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Standard radiometer w(NASA GSFC “Cry
with typical cal targetyo” target shown)
Electromagnetics Division
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Electromagnetics Division
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Radiometric TargRadiometric Targ(NOAA GS
360
350
360
K)
He
330
340
empe
ratu
re (K
320
Brig
htne
ss T
e
From targeMeasuredFrom targe
300
310
Targ
et
0 50 100 150 200 250Distance
290
Ambient
DistanceMeasured & predicted brightness temperatures vs
get Measurementget MeasurementSR target)
ated target
et temperature (e = 0.99)(error bars are std. unc., uc)et temperature (e = 0.98)
300 350 400 450 500(cm)
target
Electromagnetics Division
(cm)s. separation distance.
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Alternative: StAlternative: St
AIMR Target
andard Targetandard Target
GSFC “Cryo” Target
Electromagnetics Division
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Proposed ComRadiometer
I d d t li tiIndependent realizations oIndependent, full uncertainCombined (full) standard wof the two
− Possible √2 uncertain
Transfering the TB standarg B
− A second (portable) tstandard
− Measuring a customewith the full standard
bined Standardr and Target
f Tof TB
nty analyseswould be a weighted average
nty improvement vs. single std.
rd would involve either:target calibrated with the full
er’s target or radiometer at NIST
Electromagnetics Division
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Detector nonliDetector nonli
0.45T = 10 °CT = 30 °CT = 20 °C
ZL
0 43mV/μW
)
0.43
nsiti
vity
(m
0.41
Se
0.390.1 10.1 1
Input P
inearity studyinearity study
= 125 Ω
10
Electromagnetics Division
10
ower (μW)
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St d d tStandard termmicrowavemicrowave
(a.k.a. “Diction
Developed in cooperation(W ki G C l(Working Group on Cal-
Link (including all relevan( ghttp://www.nist.gov/eeel/e
ronics/noise project cfmronics/noise_project.cfm
i l fminology forradiometryradiometrynary Project”)
n with CEOS WGCV V l)-Val)t publications) at:p )
electromagnetics/rf_electmm
Electromagnetics Division
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Current ACurrent A
R fl ti it MReflectivity Measureme− 2 horns, 3 targets,− Additional absorbe
Expanded RadiometerExpanded Radiometer Measurements
Additional horns a− Additional horns a− Better alignment (
transit)transit)
ActivitiesActivities
tents, 2 temperatureser materialsFree-SpaceFree Space
and targetsand targetsfixturing and surveyor’s
Electromagnetics Division
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Current ACurrent A
Ab b• Absorber measuremen• Three WG bands (WR -9
• Fixturing up to WR-10
• Five concentrations of fe
• Plans for measuring cast
• Free-space absorber m• Multiple absorber samples
• Ensemble detection ex
ActivitiesActivities
t i idts in waveguide90, 62, 42)
errous-doped epoxy (machinable)
table material
measurementss
periments with GSFC
Electromagnetics Division
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MIR Calibration Targets (Coourtesy P. Racette, GSFC)
Electromagnetics Division
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Radiometer MMeasur
/ Reflectivity trements
Electromagnetics Division
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Reflectivity MeasurementsC i l dConical and Pyramidal Standard G i HGain HornsVector Network AnalyzerMultiple Horn-to-Multiple Horn totarget distancesAmbient & heatedAmbient & heatedNext: full emissivity
Electromagnetics Division
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GSFC “Cryoo” target |Γ|
Electromagnetics Division
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GSFC “Cryoo” target |Γ|
Electromagnetics Division
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GSFC “Cryo” tarrget: flat plate |Γ|
Electromagnetics Division
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Radiometric setuup – GSFC target
Electromagnetics Division
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Target AbsorberTarget Absorber
I idIn waveguide− Measuring perm
frequencies bey− Discovered batc
sample set− Plans to measu
Free spaceMeasurement te− Measurement te
− Several sample
r Measurementsr Measurements
meability and permittivity for yond those provided by mfr.ch-to-batch variation in one
ure castable material
echnique verifiedechnique verifiedes obtained for testing
Electromagnetics Division
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Permittivity M(showing batch-to
Measurements o-batch variation)
Electromagnetics Division
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Additional CAdditional C
C l bilit dComplex permeability andmaterials (in waveguide)
S lid ( i t− Solids (e.g., moist so− Liquids (e.g., salt wat
G (− Gasses (e.g., greenh
Noise diode and cold-FETh t i ti (T t bilitcharacterization (T; stabilit
Detector nonlinearityAntenna characterization (field pattern transformation
CapabilitiesCapabilities
itti it f permittivity of many
il)oil)ter)
)house gases)
T internal cal source t )ty)
(pattern, gain, near-to-far-n)
Electromagnetics Division
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SummThe need for a national (i.e
standard is being recognstandard is being recognthe remote-sensing com
S b t ti l dSubstantial progress made“foundational” aspects o
Propose a combined standPotential reduction in uncertaintyProvides a means for checking a
Initial development would extend up to 65 GHz
Working on special test cho g o spec a test c
maryye., SI-based) TBnized and accepted innized and accepted in
mmunityt NIST ie at NIST on various
of a TB standarddard radiometer+target
ynd transfer
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Next: Special tes
Temperature MonitoringElectronics
Ambient
WaveguideRadiometer
Ambient Noise
Standard
Horn
Waveguide Switch
CryogenicNoise
Standard
st chamberTemperature Sensors
MountingPlate
Absorber
Housing
Ai Ci l
n
Air Circulator
Target
Temperature Control
Air circulator
pAnd Alignment Systems
Electromagnetics Division
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SummSummDevelopment of a microDevelopment of a microtemperature standard isNIST h l i lNIST has multiple capaand post-launch cal/valOther support tests andavailable in the interimYour input and suggest
“Th b tt d t“The better you understathe easier it is to analyzetransfer function” –D Kutransfer function D. Ku
marymaryowave brightnessowave brightness s non-trivialbili iabilities to support pre-efforts
d collaborations are
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