Feasibility Study for Reconstructing the Spatial-Temporal Structure - - PowerPoint PPT Presentation

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Feasibility Study for Reconstructing the Spatial-Temporal Structure of TIDs from High-Resolution Backscatter Ionograms

• Dr. L. J. Nickisch, Dr. Sergey Fridman, Dr.

Mark Hausman

NorthWest Research Associates, Monterey, California

• Dr. Geoffrey S. San Antonio

Naval Research Laboratory, Radar Division Presented at the 2015 Ionospheric Effects Symposium 12 May 2015

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Motivation

• Medium-scale TIDs can cause large geolocation

errors for over-the-horizon (OTH) radar

– Apparent target location swings of tens of kilometers in 5-10 minutes

Azimuth 80 km Time duration: 2.5 hours

• ROTHR-Virginia

return from stationary transponder in Jamaica

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Motivation (cont.)

• OTH radars routinely collect backscatter

soundings

– Wide Sweep Backscatter Ionogram (WSBI) – Surface clutter returns as a function of delay and transmission frequency for a span of azimuths

• Can information from WSBIs be used to infer TID

structure in real time?

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GPS Ionospheric Inversion (GPSII)

• The algorithm can assimilate diverse TEC-related data
• btained on transionospheric propagation paths

– GPS L1/L2 beacon signals ⇒ GPSII

> Dual frequency group delay data (absolute TEC) > Dual frequency phase delay data (relative TEC)

– TEC data obtained with LEO beacons – Occultation-type oblique TEC from space-based receivers (CHAMP, COSMIC, DORIS)

• Other data types

– Vertical/Oblique soundings (especially important for HF skywave applications) – HF backscatter soundings – On-board plasma density measurements from satellites (such as CHAMP, DMSP) – Doppler sounding data

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The Ionospheric Reconstruction Problem: Tikhonov Method

{ }

] [ Biases )}, , ( { ) , ( ) , (

) , (

U M Y t u U e t N t N

t u

≈ = = r r r

r

Y is the set of measured absolute/relative TEC values and data points from other types of ionospheric measurements.

• The nonlinear optimization problem is solved iteratively (Newton-

Kontorovich).

1 ) dim( ]) [ ( ]) [ (

1

≤ − −

−

Y U M Y S U M Y

T

min

1

→

− U

P U T

• The pseudo-covariance P matrix is defined in such a way that the

stabilizing functional tends to take on larger values for unreasonably behaving solutions (“reasonable”  “smooth”).

There are infinitely many such solutions: The smoothest solution is selected by minimizing the stabilizing functional The solution must fit the data within errors of measurements.

Error covariance matrix Pseudo-covariance matrix

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Synthetic Wide-Sweep Backscatter Ionogram

Generated by NWRA HiCIRF code

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Real OTHR Backscatter Ionogram

Encompasses ~10° azimuthal swath

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Can WSBI leading edge structure be assimilated to expose TIDs?

• ROTHR WSBIs are collected using only the end 28 elements
• f its 372 element receive array

– Yields ~10° azimuthal resolution

• Use of full aperture would allow WSBIs with ~1° spacing

– Allows detection of leading edge TID structure

• Assimilating WSBI leading edge data would be an excellent

way of mitigating TID effects on OTHR CR

– WSBIs are routinely collected by OTHR – WSBIs densely sample the OTHR operational field of view – Modern digital technology will allow next generation OTHR to collect WSBIs using the full receive aperture without impacting the surveillance mission of the radar

• Full-aperture WSBIs were collected on ROTHR by Dr. Geoff

San Antonio (NRL) in an experimental configuration of ROTHR

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High-Resolution Leading Edge Data

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1000 2000 3000 4000

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1000 2000 3000 4000 WSBI Leading Edge as Function of Frequency

Full aperture WSBI leading edge measurements collected by Dr. Geoffrey San Antonio (NRL) Simulated WSBI leading edges using NWRA ray tracing in TID model Color contours span 15 (blue) to 27 (red) MHz

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The Hooke TID model was incorporated into NWRA’s ray tracing code

• Hooke, W. H., “Ionospheric irregularities produced by internal

atmospheric gravity waves,” Geophysical Monograph Series, The Upper Atmosphere in Motion, Vol. 18, pp. 780-808, 1968

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Generated synthetic high-resolution WSBI leading edge data: Known truth data

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16 18 20 22 24 26 28 30 32 34

Longitude Latitude 15JAN14-1900 Leading Edge 10-24 MHz Blue → Red

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Modified GPSII to assimilate hi-res leading edge data

n n n n

U U U ν + γ + γ =

− − 2 2 1 1

s

t t

e T t e

τ ∆ − τ ∆ −

− = γ ∆ π = γ

2 2 1

2 cos 2

f s f s

t t t t

e e e

τ ∆ − τ ∆ − τ ∆ − τ ∆ −

− = γ + = γ

2 1

∑

− = α + α α +

        − − =

2 1 1

) (

i i i i

x x x x v f x F

            − + + − + − − + − =

− 2 3 2 3 2 3 2 3 ] 2 : 1 [

4 3 2 5 3 2 2 1 ) ( t t t t t t t t t t t v

                        − + + + − − + − + − + + + − + − + + − − + − − + + − − + − + =

+ + − − + + − − + + − − − − + + − − − − + + + − −

) ( ) 1 ( 1 1 ) 1 1 2 3 ( ) 1 1 2 ( 1 1 ) 1 1 2 3 ( ) 1 1 2 ( ) 2 ( ) 1 ( 1 ) (

2 3 2 3 2 3 2 3 ] 2 : 1 [

t t d d t d d t d d d d t d d d d t d d t d d d d t d d d d t t t d d t v

1 1 1 2 1 1 2 1 2 1 1 1 , ,

, , ) , , (

+ + + − = γ + γ − = β − = α + β + α γ + β + α +

< ≤ < ≤ < ≤         − −         − −         − − = ∑ ∑ ∑

k k k k i i k k k z j j j y i i i x k j i

z z z y y y x x x z z z z v y y y y v x x x x v f z y x F

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Sample Input Data

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Longitude Latitude 15JAN14-1920 Leading Edge 10-24 MHz Blue → Red

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16 18 20 22 24 26 28 30 32 34

Longitude Latitude 15JAN14-1924 Leading Edge 10-24 MHz Blue → Red

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16 18 20 22 24 26 28 30 32 34

Longitude Latitude 15JAN14-1928 Leading Edge 10-24 MHz Blue → Red

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16 18 20 22 24 26 28 30 32 34

Longitude Latitude 15JAN14-1932 Leading Edge 10-24 MHz Blue → Red

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16 18 20 22 24 26 28 30 32 34

Longitude Latitude 15JAN14-1936 Leading Edge 10-24 MHz Blue → Red

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16 18 20 22 24 26 28 30 32 34

Longitude Latitude 15JAN14-1940 Leading Edge 10-24 MHz Blue → Red

Samples separated by 4 minutes in time spanning 20 minute period of TID

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Sample Output: Plasma frequency (MHz) at 250 km altitude

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Comparison of Output to Truth Output Truth

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Future plans

• Result of synthetic feasibility study is

encouraging

• This work will continue over the next two years

– Collect full aperture WSBI data on ROTHR in conjunction with fixed transponder data – Add capability for assimilating surface clutter Doppler data – Field and ASTRA TIDDBIT system in the field of view of ROTHR to collect independent TID data for comparison (Dr. Geoff Crowley)