time stability of the k-band catalog sources · using the allan variance to determine noise floor...

Time stability of the K-band catalog sources

K.LeBail(1),A.deWi1(2),C.S.Jacobs(3),D.Gordon(1)(1)NVI,Inc.,NASA/GSFC(code61A),Greenbelt,MD,U.-S.

(2)SARAO/HartRAO,Krugersdorp,SouthAfrica(3)JetPropulsionLaboratory,CaliforniaInst.Technology/NASA,Pasadena,CA,U.-S.

24thMeeUngoftheEuropeanVLBIGroupforGeodesyandAstrometry(EVGA)March17-192019,LasPalmas,GranCanaria,Spain

Acknowledgements: Copyright ©2019. All Rights Reserved. U.S. Government sponsorship acknowledged for work done at JPL-Caltech under a contract with NASA. The VLBA is managed by NRAO, funded by the National Science Foundation, and operated under cooperative agreement by Associated Universities. The authors gratefully acknowledge use of the VLBA under the USNO’s time allocation. This work supports USNO’s ongoing research into the celestial reference frame and geodesy. HartRAO is a facility of the National Research Foundation (NRF) of South Africa. The Hobart telescope is operated by the University of Tasmania and this research has been supported by AuScope Ltd., funded under the National Collaborative Research Infrastructure Strategy (NCRIS).

Outline

• K-bandinICRF3• BriefreviewonhowtousetheAllanvariancetodeterminenoisefloorofsourceUmeseries

• NoisefloorofthelatestGSFCK-bandUmeseriessoluUonandcomparisonwiththelatestGSFCS/XUmeseriessoluUonon3differentsets

2/1624thMeeUngoftheEuropeanVLBIGroupforGeodesyandAstrometry(EVGA)March17-192019,LasPalmas,GranCanaria,Spain

K-band

K-bandinICRF3

3/16

Ksolu'on S/Xsolu'on

Source# 906 4775

Session# 65 6271

ObservaUonperiod

05/2002–11/2018

08/1979–01/2019

Source#(≥10sessions)

354 788

SeeposterP306:A.deWi1etal.,“TheK-band(24GHz)CelesUalReferenceFrame”.

Thispaper:StudyofthelatestGSFCUmeseriessoluUonsforKandS/X.

−80 −60 −40 −20 0 20 40 60 800

20

40

60

80

100

Declination (deg)

Sour

ce n

oise

(µas

)

ICRF3 decimation test − Right Ascension

S/X noise floorK noise floor

−80 −60 −40 −20 0 20 40 60 800

20

40

60

80

100

Declination (deg)

Sour

ce n

oise

(µas

)

ICRF3 decimation test − Declination


310commonsources


0

20

40

60

80

100

-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90

S/Xnoisefloor Knoisefloor

0

20

40

60

80

100

-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90

S/Xnoisefloor Knoisefloor

K-band and S/X-band Position time series examples

DifferentwaystolookattheseUmeseries:

•  StandarddeviaUon=>staUcquanUty;

•  NoisefloordeterminedwiththeAllanvariance=>takesintoaccounttheUmevariable.

4/16

1980 1985 1990 1995 2000 2005 2010 2015 2020−1

−0.5

0

0.5

1

RAcosDEC (mas) 0552+398

S/X Standard dev: 1.512 K Standard dev: 0.139

S/XK

1980 1985 1990 1995 2000 2005 2010 2015 2020−1

−0.5

0

0.5

1

DEC (mas) 0552+398


S/XK

1980 1985 1990 1995 2000 2005 2010 2015 2020−1

−0.5

0

0.5

1

RAcosDEC (mas) 3C120


S/XK

1980 1985 1990 1995 2000 2005 2010 2015 2020−1

−0.5

0

0.5

1

DEC (mas) 3C120


S/XK


Using the Allan variance to determine noise floor (1/2)

-1 Whitenoise

0 Flickernoise

+1 Randomwalk

5/16

•  TheAllanvarianceisastaUsUcaltoolthatgivesthelevelandtypeofnoiseofUmeseries.

•  IfarethemeasurementsandτthesamplingUme,theAllanvarianceis:

•  Typeofnoisedeterminedbytheslopeofthecurve:€

xi( )i=1,n

€

σ2 τ( ) =12

xi+1 − xi( )2

€

log10 σ2( ) = f log10 τ( )( )


Whitenoise Flickernoise Randomwalk

Realdata:sourcesnotobservedregularly=>difficulUesinstaUsUcaldeterminaUonduetogapsinbetweenobservaUons,numberofobservaUons,…PreprocessingoftheUmeseries.•  Step1:Keepsourceswith10ormoreobservaUons.•  Step2:Averaging(yearlyandmonthly)andinterpolaUon.Thresholdcut-offwheninterpolaUng.

•  Step3:Allanvarianceprocessingforeachsource,eachcoordinate,eachaveragedUmeseries.

•  Step4:NoisefloordeterminaUonforeachsourceandeachcoordinate.WelookatthenoisetypedeterminedbytheslopeoftheAllanvariancecurve:

•  Whitenoiseorflickernoise:thenoiseflooristhelowestAllanvariancevalue.•  Randomwalk:sourcerejected.

6/16

Using the Allan variance to determine noise floor (2/2)


Comparison 1/3 310 common sources – Period 1979-now

TheKnoisefloorstendtobesmallerthantheS/Xnoisefloors.

7/16

StandarddeviaUonNoisefloordeterminedby

theAllanvariance

500 1000 1500 20000

20

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100

120

140

Source standard deviation (µas)

Sour

ce n

umbe

r

RAcos(DEC) − K−band

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120

140DEC − K−band


Sour

ce n

umbe

r

500 1000 1500 20000

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120

140


Sour

ce n

umbe

r

RAcos(DEC) − S/X−band

500 1000 1500 20000

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40

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100

120

140DEC − S/X−band


Sour

ce n

umbe

r

100 200 300 400 5000

10

20

30

40

50

60RAcos(DEC) − K−band

Source noise floor (µas)

Sour

ce n

umbe

r

100 200 300 400 5000

10

20

30

40

50

60DEC − K−band


Sour

ce n

umbe

r

100 200 300 400 5000

10

20

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60RAcos(DEC) − S/X−band


Sour

ce n

umbe

r

100 200 300 400 5000

10

20

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40

50



Sour

ce n

umbe

r


Comparison 1/3 310 common sources – Period 1979-now

Noisefloorcomparisonin

10odeclinaUonbands

8/16

−80 −60 −40 −20 0 20 40 60 800

100

200

300

400

500

Declination (deg)So

urce

noi

se fl

oor (µ

as) RAcos(DEC)


−80 −60 −40 −20 0 20 40 60 800

100

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500

Declination (deg)

Sour

ce n

oise

floo

r (µ

as) DEC



Comparison 2/3 87 common sources – Period 11/2016-11/2018

FocusonsameperiodofobservaUon:

November2016toNovember2018.

9/16

1980 1985 1990 1995 2000 2005 2010 2015

S/X sessionsK sessions

Ksolu'on S/Xsolu'on

Source# 901 4728

Session# 44 391

Source#(≥10sessions) 254 431

87commonsources



10/16

2016.5 2017 2017.5 2018 2018.5 2019 2019.5−1

−0.5

0

0.5

1



S/XK

2016.5 2017 2017.5 2018 2018.5 2019 2019.5−1

−0.5

0

0.5

1

DEC (mas) 0552+398


S/XK

2016.5 2017 2017.5 2018 2018.5 2019 2019.5−1

−0.5

0

0.5

1



S/XK

2016.5 2017 2017.5 2018 2018.5 2019 2019.5−1

−0.5

0

0.5

1

DEC (mas) 3C120


S/XK



TheS/XnoisefloorstendtobesmallerthantheKnoisefloors.

11/16

500 1000 1500 20000

5

10

15

20

25

30

35

40


Sour

ce n

umbe

r

RAcos(DEC) − K−band

500 1000 1500 20000

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35

40DEC − K−band


Sour

ce n

umbe

r

500 1000 1500 20000

5

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Source standard deviation (µas)So

urce

num

ber


500 1000 1500 20000

5

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25

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35



Sour

ce n

umbe

r

100 200 300 400 5000

5

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Sour

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umbe

r

100 200 300 400 5000

5

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20DEC − K−band


Sour

ce n

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r

100 200 300 400 5000

5

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Sour

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umbe

r

100 200 300 400 5000

5

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Sour

ce n

umbe

r


theAllanvariance



12/16

−80 −60 −40 −20 0 20 40 60 800

100

200

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500

Declination (deg)So

urce

noi

se fl

oor (µ

as) RAcos(DEC)


−80 −60 −40 −20 0 20 40 60 800

100

200

300

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500

Declination (deg)

Sour

ce n

oise

floo

r (µ

as) DEC



10odeclinaUonbands


Comparison 3/3 31 common sources - VLBA sessions

•  UDsessions:24-hourVLBAsessionsatK-band.•  UF001andUG002sessions:24-hourVLBAsessionsatS/Xband.Goals:improvingtheprecisionofICRF3,ICRF3maintenance,andfutureupdatesoftheICRFatradiofrequencies.Approximately3300oftheweakestICRF3sourceswillbere-observedduringthesesessions.

13/16

Ksolu'on S/Xsolu'on

Source# 819 4145

Session# 27 40

Source#(≥10sessions)

149 132

2016.5 2017 2017.5 2018 2018.5 2019 2019.5−1

−0.5

0

0.5

1



S/XK

2016.5 2017 2017.5 2018 2018.5 2019 2019.5−1

−0.5

0

0.5

1

DEC (mas) 0552+398


S/XK

31commonsources



TheKnoisefloorsandtheS/Xnoisefloorsseemtobeequivalent.

14/16

500 1000 1500 20000

5

10

15


Sour

ce n

umbe

r

RAcos(DEC) − K

500 1000 1500 20000

5

10

15DEC − K−band


Sour

ce n

umbe

r

500 1000 1500 20000

5

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15


Sour

ce n

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r


500 1000 1500 20000

5

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Sour

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r

100 200 300 400 5000

5

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Sour

ce n

umbe

r

100 200 300 400 5000

5

10

15DEC − K−band


Sour

ce n

umbe

r

100 200 300 400 5000

5

10



Sour

ce n

umbe

r

100 200 300 400 5000

5

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Sour

ce n

umbe

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theAllanvariance



15/16

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Declination (deg)So

urce

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oor (µ

as) RAcos(DEC)


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Declination (deg)

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as) DEC



10odeclinaUonbands


Conclusions

•  K-bandUmestability•  TheK-bandobservaUonshavereachedalevelofstabilityequivalenttothelevelofcurrentS/XobservaUons.

•  ThestrengthoftheS/Xdatasetisinitsbroaddiversityofbaselinesandsessions.

•  WeneedtoconUnuemonitoringtheK-bandobservaUonsandcomparingthestabilityoftheframerealizedbytheK-bandobservaUonswiththeS/Xframe.

16/16

•  ThankstotheVLBA,K-bandobservaUonshaveincreasedgreatlyinthepasttwoyears,prompUngmanystudies.Atthe2019EVGA:

•  BenediktSoja:“IonosphericcalibraUonforK-bandcelesUalreferenceframes”.•  HanaKrásná:“EarthorientaUonparametersesUmatedfromK-bandVLBA

measurements”.•  AlethadeWi1:“TheK-band(24GHz)CelesUalReferenceFrame”.


Thank you


And more…

Structure,propermoUon?

1980 1985 1990 1995 2000 2005 2010 2015 2020−1

−0.5

0

0.5

1



S/XK

1980 1985 1990 1995 2000 2005 2010 2015 2020−1

−0.5

0

0.5

1

DEC (mas) 3C418


S/XK


Noise floor comparison Individual sources

StandarddeviaUon

0 500 1000 1500 20000

500

1000

1500

2000

RAcos(DEC)

S/X source standard deviation (µas)

K so

urce

sta

ndar

d de

viat

ion

(µas

)

0 500 1000 1500 20000

500

1000

1500

2000

DEC


K so

urce

sta

ndar

d de

viat

ion

(µas

)

0 100 200 300 400 5000

100

200

300

400

500

RAcos(DEC)

S/X source noise floor (µas)

K so

urce

noi

se fl

oor (µ

as)

0 100 200 300 400 5000

100

200

300

400

500

DEC


K so

urce

noi

se fl

oor (µ

as)

0 100 200 300 400 5000

100

200

300

400

500

RAcos(DEC)


K so

urce

noi

se fl

oor (µ

as)

0 100 200 300 400 5000

100

200

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400

500

DEC


K so

urce

noi

se fl

oor (µ

as)

0 500 1000 1500 20000

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1500

2000

RAcos(DEC)


K so

urce

sta

ndar

d de

viat

ion

(µas

)

0 500 1000 1500 20000

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1500

2000

DEC


K so

urce

sta

ndar

d de

viat

ion

(µas

)

0 500 1000 1500 20000

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RAcos(DEC)


K so

urce

sta

ndar

d de

viat

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(µas

)

0 500 1000 1500 20000

500

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DEC


K so

urce

sta

ndar

d de

viat

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(µas

)

NoisefloordeterminedbytheAllanvariance

0 100 200 300 400 5000

100

200

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500

RAcos(DEC)


K so

urce

noi

se fl

oor (µ

as)

0 100 200 300 400 5000

100

200

300

400

500

DEC


K so

urce

noi

se fl

oor (µ

as)

(157

/142

sou

rces)

En'reperiod

(310

sou

rces)

(74sources)

2-yrpe

riod

(87sources)

(24/28

sou

rces)

VLBAsession

s(3

1sources)


time stability of the k-band catalog sources · using the allan variance to determine noise floor...

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