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
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
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
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
Electromagnetics Division
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
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
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
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
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)
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
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
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
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
Electromagnetics Division
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
IR Thermal ImIR Thermal Immage of Targetmage of Target
Electromagnetics Division
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
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)
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)
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
Standard radiometer w(NASA GSFC “Cry
with typical cal targetyo” target shown)
Electromagnetics Division
Electromagnetics Division
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.
Alternative: StAlternative: St
AIMR Target
andard Targetandard Target
GSFC “Cryo” Target
Electromagnetics Division
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
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)
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
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
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
MIR Calibration Targets (Coourtesy P. Racette, GSFC)
Electromagnetics Division
Radiometer MMeasur
/ Reflectivity trements
Electromagnetics Division
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
GSFC “Cryoo” target |Γ|
Electromagnetics Division
GSFC “Cryoo” target |Γ|
Electromagnetics Division
GSFC “Cryo” tarrget: flat plate |Γ|
Electromagnetics Division
Radiometric setuup – GSFC target
Electromagnetics Division
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
Permittivity M(showing batch-to
Measurements o-batch variation)
Electromagnetics Division
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
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
be 18-26.5 GHz band;
hamber…Electromagnetics Division
a be
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
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
tions are welcomedd th t f th tand the parts of the system,
e (or re-analyze) the system unkee
Electromagnetics Division
unkee