ARL

Applied Research Laboratories The University of Texas at Austin

LWA Ionospherically Related Work at ARL:UT

Dr. Gary S. Bust

ARLApplied Research Laboratories The University of Texas at Austin

Outline

Ionospheric Calibration of LWA History and Capabilities of IDA3D Results from IDA3D IDA3D applied to LWA Future Directions at ARL:UT as they apply to LWA

ARLApplied Research Laboratories The University of Texas at Austin

Ionospheric Calibration of LWA

~ 50 stations spaced over a 300 - 400 kilometer region. Each station consists of ~256 antennas over a 100 x 100

meter region. The primary beam of a station is ~2 degrees x 2 degrees (~

12x12 km at 300 km) Know phase to ~ 1 degree everywhere in beam.

ARLApplied Research Laboratories The University of Texas at Austin

Ionospheric Requirements

1 degree phase requirement: Know TEC to ~ 10-4 TECU (~ 100 times greater accuracy than GPS phase measurements)

At this sensitivity, need measurements every few seconds Possibly need to specify TEC on scales of 1 km or less Need to specify some kind of ionospheric map at each of 50

stations over a 300+ km baseline

ARLApplied Research Laboratories The University of Texas at Austin

Measurement Equation Simple version of visibility integral equation between two stations: Actual equation includes effects of polarization, projection,leakage,electronic

gain etc. And also integration in time and bandwidth.

€

rαβ u,v( ) = I l,m( )∫∫ A l,m( )e−i2π lu+mv( )e−i φα

I l,m( )−φβI l,m( )( )dldm (1)

u = Dλ ⋅ ˆ x

v =Dλ ⋅ˆ y

l = sin(θ)cos(φ)

m = sin(θ)sin(φ)

τ = lu + mv

ARLApplied Research Laboratories The University of Texas at Austin

Issues Regarding Calibration

Astronomers need the ionospheric phase calibrated for each station, and everywhere within each station primary beam.

~ 50 stations. Say we need it every 1 km in a 10 x 10 km beam Direct approach ~ 100 parameters per station ~ 5000

unknowns. But, if we have 50 stations we have 50*49/2 ~ 1,250

visibilities per calibrations source.

ARLApplied Research Laboratories The University of Texas at Austin

Issues Regarding Measurement Equation

Non-linear forward integral model in the ionospheric phases Cannot necessarily bring ionospheric phases outside integral Cannot do synthesis via fourier transform of visibility Need ~ 100 sources in primary beam. Need to solve for visibilities for all 100 sources, between all

stations For 50 stations ~ 125,000 visibilities

ARLApplied Research Laboratories The University of Texas at Austin

Inversion Approaches

Use visibility data and measurement equation Must solve for a non-linear integral equation to estimate

ionospheric phases ~ 100,000 measurements, ~ 5000 unknowns. That is good!!! Waves: If we require 2D spatial from 1-300 km we have ~

1e5 unknowns -- not good!!! So, be more clever - wavelets? Different waves at each station?

Elevation / station Pixels

ARLApplied Research Laboratories The University of Texas at Austin

VLA Calibration

ARLApplied Research Laboratories The University of Texas at Austin

Calibration Plan and Schedule

FY07 Develop forward simulation of visibilities including ionospheric simulations

and simulated sky map Develop initial inversion algorithm Test algorithm on simulated data

FY08 Test algorithm on historical VLA data and data with Pie Town Improved forward simulation Refined inversion algorithm

FY09 Test algorithm on new VLA / Pie Town experiments with LWA stations

added Collaborate / Exchange results and ideas with LOFAR

Good working collaboration with Jan Noordam ASTRON Netherlands

ARLApplied Research Laboratories The University of Texas at Austin

From MACE’93 to IDA3D: Ionospheric Imaging at ARL:UT

Ionospheric Imaging Algorithms at AR:UT Simulations 1992 Mart 2D tomography 1992-1994 First 3D/4D algorithm (1995-1998)

GPS + CIT + Ionosondes 3D First 3D algorithms in the literature Origins of IDA3D

True development of IDA3D as assimilation began in 1998 3DVAR objective analysis Development continuing at present

Experimental campaigns and instrumentations 12 experimental campaigns since 1992 Took over operations of Transit (now NIMS) for Navy (1996) Developed CIDR – replacement for Magnavox 1502 (2000)

ARLApplied Research Laboratories The University of Texas at Austin

ARL:UT Tomography Data Assimilation Experiments

Mace: Days 181-349 1993 9 receivers ICMT1: Days 24-46 1995 2 5 receiver arrays ICMT2: Days 80-110 1996 3 5 receiver arrays RadWhite: Days 267-355 1996 (ICMT1 Config) Traits: Days 183-365 1997 (Caribbean)

Days 28-35 1998 PR Heater Days 21-28 1998 (8 receivers @ PR) CIC1 Days 173-182 1998 (Caribbean) PrairieDog Days 190-278 1998 (West and East Cst) CIC2 Days 250-273 1999 (Caribbean) Alaska Day 285 - ? 2000 - Current Greenland Day 278 - ? 2000 - Current NECA Day 325 - ? 2002 - Current

ARLApplied Research Laboratories The University of Texas at Austin

Overview of IDA3D Solves spatial 3D tomographic inverse problem - maximum

likelihood solution Equivalent to 3DVAR in meteorology Solution also known as Kalman gain Important inverse imaging math and development is in the choice of

background model, model error covariance and data error covariance

Solution updated at user selected intervals (typically 5-15 minutes)

Verified and validated many times IDA3D has validated against altitude distribution of plasma

density in addition to TEC validation

ARLApplied Research Laboratories The University of Texas at Austin

Capabilities of IDA3D Flexible

User can input customized irregular grid User can input any model empirical or physical Flexible error covariance data base inputs Entire program designed to be customized by user

Global globally and regionally Storms and quiet times

Data types Accepts large number of different data types currently Designed modularly to make easy to add new data sets.

ARLApplied Research Laboratories The University of Texas at Austin

IDA3D Current Status of Development

Data Sources Ground Based

GPS TEC Tomography: Greenland, Alaska, NECA, Equatorial CIDR arrays EISCAT, Sondrestrom, Millstone Hill ISR’s

Space Based In-situ DMSP, CHAMP, ROCSAT Occultations: Champ, SACC, GRACE, IOX OSEC: Champ, SACC, GRACE TOPEX TEC

Models IRI, PIM, TIMEGCM, RIBG

Recent Improvements Now solve for state vector log10(Ne) Assimilate ionosonde virtual heights versus frequency Run in parallel on 24 processor cluster

ARLApplied Research Laboratories The University of Texas at Austin

Validation of Tomography and IDA3D

Mid-America Computerized Ionospheric Tomography Experiment (MACE): 1993 Comparisons with ionosonde virtual heights

Virtual height error ~ 6% foF2 error 1.9-3.2 %

Single Sight Location (SSL) experiments On 1650 km path, range error ~ 9% compared to 15% using classical

SSL methods

ARLApplied Research Laboratories The University of Texas at Austin

Ionosonde Virtual Height Comparisons MACE

Papers: 1) “Application of ionospheric tomography tosingle-site location rangeestimation” Bust et al.,1994, J. Imaging Sys. andTech.2) “Mid-America computerized ionospheric tomography experiment (MACE ‘93)”, Kronschnabl et al., 1995, Radio Science

ARLApplied Research Laboratories The University of Texas at Austin

Traits Campaign 1997

“Verification of ionospheric sensors”, C. Coker et al., 2001, Radio Science.

ARLApplied Research Laboratories The University of Texas at Austin

ISR Comparisons to IDA3D

Sondrestrom Sept 30, 2000 Oct 30, 2003

EISCAT Dec 12, 2001 Patches

Millstone Hill Nov 20, 2003 uplifts

ARLApplied Research Laboratories The University of Texas at Austin

IDA3D Sept. 30, 2000 compare to Sondestrom

Watermann et al., “Mapping plasma structures in the high-latitude ionosphere using beacon satellite, incoherent scatter radar and ground-based magnetometer observations”, Annals of Geophysics, 45, 2002

ARLApplied Research Laboratories The University of Texas at Austin

IDA3D Dec 12, 2001 compare to EISCAT

Bust, G.S. andG. Crowley, “Tracking of polar cap ionospheric patches”, submitted to J. Geophys. Res., 2006

ARLApplied Research Laboratories The University of Texas at Austin

IDA3D Oct. 30, 2003 compare to Sondestrom

ARLApplied Research Laboratories The University of Texas at Austin

IDA3D Nov. 20, 2003 compare to Millstone Hill

IDA3D sees extreme uplift in plasma 17-18 UT, as does Millstone Hill. Also notice the double E-F layers in IDA3D and Millstone Hill later.

ARLApplied Research Laboratories The University of Texas at Austin

Statistical Validation of IDA3D with ISRs

4 days in 2003. Two closer to Equinox (2003, Oct 28, Oct 30) Two closer to Solstice (2003, Nov 19, Nov 20) Two magnetically quiet days (Oct 28, Nov 19) Two disturbed days (Oct 30, Nov 20)

Days need to have ISR coverage, and good data coverage Results

Quiet Times Standard deviations of 1.0E11 and 1.5E11 el/m3 in the F-region Mean offsets of -0.3E11 and -0.5E11 el/m3

Active Times Standard deviations: 2.2E11 and 3.8E11 el/m3

Mean: 0.08E11 and -0.91E11 el/m3

ARLApplied Research Laboratories The University of Texas at Austin

IDA3D Movies of Scientific Results

Oct 30, 2003 polar VTEC movie November 20, 3003 slice along 290 longitude Oct 30, 2003 VTEC Movie over the USA Oct 30, 2003 slice movie over the USA

ARLApplied Research Laboratories The University of Texas at Austin

Oct 30, 2003 Polar Movie

QuickTime™ and a decompressor

are needed to see this picture.

ARLApplied Research Laboratories The University of Texas at Austin

Oct 30, 2003 VTEC over the USA with data

coverage

QuickTime™ and aPNG decompressor

are needed to see this picture.

ARLApplied Research Laboratories The University of Texas at Austin

Oct 30, 2003 slice at 260 longitude. Log Density.

QuickTime™ and aPNG decompressor

are needed to see this picture.

ARLApplied Research Laboratories The University of Texas at Austin

IDA3D and LWA

Large scale imaging 300+ km horizontal ~ 10-25 km resolution ~ 100 look directions (maybe more) every 10 seconds, 50 stations ->

~ 5000 data points. Ingest into IDA3D and do high-resolution regional imaging every

few seconds Japan GPS network is similar in many ways

~ 1000 receivers separated by ~ 10 km. Currently see 6-10 satellites ~ 6000 data points Same amount of data, roughly same coverage area (somewhat larger)

IDA3D has already been successfully used to image results from Japan network.

This gives us great confidence in using it with LWA

ARLApplied Research Laboratories The University of Texas at Austin

Japan 2003, Nov. 4

Altitude-latitude slice at 138 Long. over Japan. 1040 UT Nov. 4, 2003

Re-integrated VTEC from IDA3Dover Japan. 1040 UT Nov. 4 2003

ARLApplied Research Laboratories The University of Texas at Austin

Future Directions: Mesoscale and LWA

Within a primary beam ~ 1 km resolution over 12-15 km regions By crossing beams possibly look at 3D + time variations in delta

Ne

Ionospheric Regional Assimilative Model (IRAM) 2nd of two year development funded by ONR Numerical data assimilation on regional scales Expand continuity equation, electron, ion momentum, divergence

of current in perturbations of background Keep non-linear terms Assume temperature perturbations are not drivers Transform to Fourier wave-vector/frequency space Iteratively solve non-linear terms Transform back into real space-time

ARLApplied Research Laboratories The University of Texas at Austin

Future Directions: Connecting LWA to Broader Community

GPS Workshop at ARL:UT (Sept. 30-Oct. 1) Introduce LWA to GPS TEC Community - closest to LWA,

experience, ideas, algorithms Third Meeting Last one had one member of modeling / DA community

Tim Fuller Rowell Univ. of Colorado

This time invite other modelers / DA groups Get them more involved in GPS TEC community Share expertise of GPS group