T. Bullet - lisn

High Frequency RadarsandIonospheric Soundingwith VIPIRDr. Terence BullettUniversity of Colorado BoulderCooperative Institute for Research in Environmental SciencesElectrical, Computer and Energy EngineeringTerry.Bullett@noaa.govSponsored by:Jicamarca Radio Observatory Radar SchoolNovember 2013With assistance from:Robert LivingstonRichard GrubbNikolay ZabotinIn Cooperation with:National Oceanic and Atmospheric AdministrationNational Geophysical Data CenterSolar and Terrestrial Physics Division

Agenda3. VIPIR Operations● Measurement Concepts1. Ionosonde Principles● Research Topics● Resources & Credits● Earth's Ionosphere●● Ionosonde Applications VIPIR Data● Propagation in Plasma● Data Formats● Ionospheric Sounding● VIPIR Operations2. Ionosonde hardware 4. VIPIR Calibration & Misc● Historical Ionosondes● Calibration Tests● Modern Ionosondes● Free Software● VIPIR● Hardware Tour

Earth's Ionosphere●●●●●Plasma of ionized atmospheric gases●NO, O2, O, H, HeProduced by solar EUV (mostly)~50 to ~1000 km altitudeStrong temporal variations●●●DailySeasonalSolar CycleStrong interaction with Earth's magnetic field●Solar produced magnetic disturbances●High, Middle and Low Latitudes

Ionosphere Vertical Electron Density ProfileThe F2 region variesby 3-5X diurnally,highest just after noon,lowest before dawn.The F1 region and Eregion dissipate at night.--------------------------IonosondesMeasure UpTo H maxThe D region is presentonly during daytime andin times of high activity.

Radio Waves in PlasmasPlane Wave Electric FieldE z=RE oe i t−kz Index of Refraction●●●Cool plasmaNo Collisionsn= ck No Magnetic Field=−i 2 =1− X =1− f 2Nf =1− N = e22f 2 4 2 o m 80.5Propagation near the speed of light whenf N ≪ f ;≈1Propagation slows dramatically when f N f ; 0Specular (total) reflection occurs whenf N = f ;=0After Davies, 1965

Propagation with a Magnetic FieldA magneto-plasma is birefringentThe index of refraction depends on the polarization of the radio waveA magneto-plasma is anisotropticThe index of refraction depends on the direction of propagationIndex of refraction: 2 2X 1− X =1−21− X −Y 2 T ±Y 4 T 41− X 2 2Y LWith respect to the direction of propagation:The + and – refer to the Ordinary andExtraordinary polarized radio wavesReflection occurs whenf N = fX =1−YX =1Y(Ordinary wave)Y L =Longitudinal component of YY T =Transverse component of Y(eXtraordinary waves)O&X are circularly polarized over most the EarthLinearly polarized at the magnetic equatorY = BemY = f Hfef H =∣B∣2 mAfter Davies, 1965

Appleton EquationA magneto-plasma is absorptiveThe radio wave amplitude decreases as energy is lost due to collisionsThe full Appleton equation with collisionsZ = f fn 2 X=1−2Y1−iZ− T21− X −iZ ± 4Y T41− X −iZ Y 2LWith propagation below 30 MHz in the Earth's Ionosphere,all of these factors can substantially influence the radio waveThis influence provides both Great Opportunity and Great Difficulty withRemote Sensing and Radio Science with IonosondesAfter Davies, 1965

Phase and Group VelocityPhase velocity is defined as:v= c ∴v=c∞as=10Which means the radio wavelength increases in a plasmaGroup velocity is: u= d d k u=c 0 as =10k 0Which means the propagation speed decreases in a plasmaGroup Refractive Index is: ' = c u =c d kd = f d d fWith no magnetic field: ' = 1 ∴ ' =1∞as=10After Davies, 1965

Virtual Height and Density Profiles●●●Ionosondes measure the time of flight of apacket of radio frequency energyVirtual Height or Group PathIntegral of the Group Refractive IndexVirtual heighth Rh' f =∫ ' f dh0For a parabolic electron density profile:N h= f 2[p80.5 1− h−h oy m2]Virtual Height (reflection):h' f =h o − y m y m2fln f p ff p f p − fVirtual Height (through the layer) h' f =h o − y m y mff pln f f pf − f pAfter Davies, 1965(no magnetic field)

Parabolic EDP and Virtual Heighth'(0.834foF2) = hmF2hmF2foF20.834*foF2

Propagation through a LayerhmEfoE

Movie● U.S. Army Training film from 1960●●●Very basic introduction to radio wavesSurprisingly good explanation of the ionosphereand its effects on radio wave propagation45 minutes

What is an Ionosonde and what does it do?ARTISTScaling●●●●●●MF-HF Radar (1-20 MHz)A acre or ten of antennasMeasures ionospherereflection height at a precisedensity (sounding frequency)Feature recognition softwareneeded in an often compleximageInversion process requiredto obtain bottom-sideelectron density profileValleys and Topside aremodeled or extrapolated

Ionosondes: Reversed Independent Variables●●●●With most ionosphere sensors, the observationlocation is selected by the instrument●●Radar look directionSatellite orbitThe plasma density is measured●●●Radar ReflectivityLocal Plasma probeTEC along a known pathWith an ionosonde, the plasma density is set bythe frequency of observation.The measurement is the location (range, direction)of the ionosphere which has that density.

Courtesy IPSClassic Ionogram

Classic Ionogram ScalingCourtesy IPS

Digisonde 256 DataIonogram data with polarization,Doppler and autoscalingDaily plot of maximumreceived signal

Dynasonde21Jicamarca, Peru : VIPIR ionogram : Dynasonde21 AnalysisCourtesy JRO and DSL

Dynasonde21Dynasonde Ionogram AnalysisStructure Functions3D EcholocationClassical URSI scaled characteristicsEDP Time HistoryDynasonde21©Dynasonde Solutions Ltd(Courtesy Wright & Zabotin)Vector Velocities

Applications of the Modern IonosondeWright & BullettAdv Sp. Res. 2000Auto-ProcessedDynasondeIonogramGroup and 'True' Ranges / km500400300200150120100Echo Recognition by PRETEC; Trace Classes by ECL; N(h) by POLAN-x x--zzz oo o o oo ooo ooo ooo oz z- -oo o oo o zzoo o oo o oooo- -- - -- ---- - --- -- ------- - - -- ----- --- - -- ---

●●Plasma Physics with IonosondesCareful examination of changes in transmittedradio wave properties:●Amplitude, Range, Frequency, Doppler, Direction, PhaseDetermine the plasma properties●●●●●●DensitiesWavesTurbulenceStructureCompositionPhysical Processes●NaturalIrregularity Amplitude ΔN/N0.11E-21E-31E-41E-5● Artificial1E-2 0.1 1 1E+1 1E+2 1E+31λMultipleScattering(AnomalousAttenuationEffect;Range Spread;Lacuna Effect)Diffraction(PhaseStructure FunctionMethod)L FMultibeamReflections(Spread F;Δf/f Method;PolarizationDistortions;S 2, S 3Indices)Tilts, AGWs(Echolocation;Doppler)Small Intermediate Mid LargeIrregularity Scales, kmCourtesy Wright & Zabotin

Modern Data AnalysisData Analysis Techniquesfor use onModern Ionosondes“Making sense of an ocean of raw data”

Analysis Background●●High SNR values allow for several options●●●Build a small and/or cheap radarIntegrate / pulse compress to get your SNR backDigisonde, CADI, AIS, etcBuild a good radar and exploit the opportunities●●●●●Stable single-pulse statisticsPrecision techniquesRapid measurementsScientific DiscoveryDynasonde, FAR, VIPIR

Polarization●●Ordinary and eXtraordinarypolarizations are circular and ofopposite rotation●Except very near the magneticequator, it is linearTwo orthogonal, linearly polarizedantennas can form a circularlypolarized antenna●●Digisondes do this in hardwareat the antennaVIPIR and Dynasonde do this inthe analysis softwareSan Juan, Puerto Rico

Circular Polarization

Circular Polarization ExampleRx2-X+90Rx1-X-90Rx1-ORx2-OSJJ18_2010308180508.RIQ●●●●●●●●Two orthogonal antennasSeparate receiversO and X mode signalsMagnitude [dB]Phase [deg]-90 for O-mode+90 for X-modePhase shift even receiverdata +90 and – 90 andsum with odd receiverdataEquatorial O/X Polarizations are orthogonal linear!

Polarization Example

●●Precision vs ResolutionResolution is the ability to separate 2 objects●●Closely spaced in some dimension (i.e. Range)Determined by waveform (bandwidth)Precision is the ability to measure a resolved object●Mostly determined by SNR

●Radar TimingT 0is the start of a Pulse Repetition Interval● Waveform is started some time after T 0●Waveform has finite duration● Receiver sampling is started some (other) time after T 0●●The PRECISE range of the received waveform is definedas the peak of the receiver impulse responseThe ACCURATE values of the range gates aredetermined by multi-hop Sporadic-E●Therefore:●●A calibration factor RANGE0 is provided as the “correct”range of the 0 th (non-existent) range gateSome range gates can have negative range if they startbefore the peak of the transmitted waveform

Waveform Timing

●●●Precision RangeUse the high SNR and precise receiver responseProperly sampled receiver outputFit a raised cosine function to the amplitude data● Ao, Ro, W Ax=Ao[ 1 x−Ro1cos2 W]4

Impulse Response FittingAo=58.6 ; Ro=166.7Ax=53.3 ; Rx=176.9Precision is about 0.1 range gate (150m)Depending on SNR and echo separation

Doppler Shift●●●Doppler shift is a change inradio phase with time due tothe change in phase pathDetails are beyond thescope of this presentationFor ionosondes, this meansa change in the ionosphereplasma●●●MotionPhotochemistryIrregularities● WavesResearch Opportunity

Doppler Example●Doppler is the first moment of the phase vs time.Higher order moments due to ionosphere structureResearch Opportunity●

Interferometry k 1 2DResearch Opportunity 2 − 1 =∣k∣D sin●●●●The phase differencebetween spacedantennas related to theangle of arrival of aplane radio waveIssues:●●●2π ambiguityNon-plane waveMutual CouplingMultiple antennas andspacings aid to resolvethis problemRoom for Improvement

Receive Array: San JuanAntennas at locations:-9 -3 -1 0 +4Gives separations of1 2 3 4 5 6 7 8 9 13Units of 7mCan use any 8 antennassimultaneously

End of Section 1Questions?

Sondrestrom (AFRL)Ascension Island (AFRL)IonosondesBear Lake (USU)Cocos Island (IPS)Scott Base (IPS)Nuie Island (IPS)Stanley, Falklands (RAL)Pakistan (SUPARCO)

Ionosonde History● The first radar, invented in 1926●●●●●Used to measure the height of the ionosphereBi-static “chirp” and mono-static “pulse” varietiesLongest ionosphere climate record~ 100 Vertical Incidence ionosondes worldwideNew technologies have evolved the ionosonde:●●●●●High power electronicsData display and recordingAntennasComputersDigital Signal Processing

Ionosonde ComponentsIonosphereTx AntennaRx Antenna(s)FrequencySynthesisReceiver(s)DataTransmitterTimingControlAnalysis

Courtesy Manila Ionosphere ObservatoryHistorical IonosondesC3 – Circa 1955 IPS42 – Circa 1975

Analog Ionogram on FilmDate and TimeFrequency MarkersReceiverOutputRange Markers

Manual Scaling SheetsA month (Jan 1946) of foF2 data from Washington DC

Digisonde – Circa 1990Recent IonosondesDynasonde – Circa 1990

NOAA Dynasonde DataCourtesy of British Antarctic SurveyCourtesy of EISCAT

Canadian Advanced Digital IonosondeSvalbardCADIAreciboCourtesy SIL

Expert System forIonogram ReductionESIRESIR-CADIESIR- Jicamarca VIPIRCourtesy Space Environment Corporationand Boston College

INGV-AISItalian Advanced Ionospheric Sounder

Autoscala●●●●●Italian automaticionogram scalingsoftwareBasic URSI scaledcharacteristicsElectron DensityProfileWorks on VIPIR,AIS,PARUSCADI?

Courtesy Hermanus Magnetic ObservatoryDPS-4D

ARTISTDirectogramVelocitiesSkymapIonogram

Vertical Incidence Pulsed Ionospheric RadarWorld Class Research Ionosonde Station, Wallops Island, VA, USATransmit AntennaVIPIRReceive Array

VIPIR Radar FeaturesVery high interference immunity: IP3 > 40 dBmHigh Dynamic Range: 115(I) +30(V) dBDirect RF sampling 14 bits at 80 MHzFully digital conversion, receiver and exciterWaveform Agility: 2 µs to 2 ms pulse/chip widthUSB-2 Data and Command/Control Interfaces8 coherent receive channels; Frequency: 0.3 – 25 MHz4 kW class AB pulse amplifier: 3rdharmonic < -30 dBcPrecise GPS timing for bi-static operationRadar software Open Source C code; runs under LinuxDesigned for extreme performance and flexibility

Upgrades for the VIPIR Mark II●●●●●●●FPGA based digital receiver16 bit, 120 MHz ADCUSB3 data transferImproved analog front endImproved receive antenna pre-amplifiersContemporary computers and data storageOptions:●●●High power low pass transmit harmonic filterRubidium oscillator for oblique phasemeasurementsLoop Receiving Antennas

Wallops Island VIPIR hardwarePower Conditioner4kW RF AmplifierKVMExciterReferenceReceiverFront EndBalunControl ComputerAnalysis ComputerUPS

Wallops Island Overview150mx250m37,500 sq. m9 acres100 m

What makes a World Class Ionosonde?Large, Efficient Transmit antennaLarge receive arrayModern, powerful sounderCo-located InstrumentsDedicated ScientistsJicamarca Incoherent Scatter RadarDelta vs Log Periodic Transmit patternsSounding Rocket

Wallops Log Periodic Transmit AntennaHeight: 36mSize: 75x75m

Transmit Antenna Performance

Typical Transmit Antenna Pattern

Receive Antennas4m dipoles , 5m high

WI937 Signal and Noise Spectrum50 dB

Radar Engineering

Radar EquationThe basic radar equation for a “small” target: (ignoring losses, etc)S= P t G t4 R 24 R 2 A r(Power_at_Target) x (Power_at Receiver) x (Effective Rx_Area)S= P G t t A r = 24 G r4 R 24 R A 2 rS= P t G t G r 24 3 R 4Target1 m wavelength1 sm target400 km range14 3=−33dB 2R 4 =−224dBhttp://www.radartutorial.eu/01.basics/rb13.en.htmlRadar

Fresnel ZoneD, AThe area over which radio reflections return “in phase”and contribute to the radar returnD= RRA== 4 RExamplesS= P t G t G r 3256 2 R 3●●R=100 km, λ=15m●D=1.2 km, A=60 dBsmR=400 km, λ=15m1256 2 =−34dB●●D=2.5 km, A=66 dBsmR=100 km, λ=300m 3R 3=−94dB●●D=5.5 km, A=75 dBsmR=400 km, λ=300mHF Radar300 m wavelength400 km range●D=11.0 km, A=80 dBsm

Specular ReflectionThe ionosphere spectacularly reflects “all” of the incident energyThe power density at the ground is equivalent to that at Range = 2HP i = P tG t4 H 2ReflectingLayerHeight =HP g = P tG t16 R 2IonosondeS= P t G t 2 G r16 R 2 4S= P tG tG r64 2 R 2164 2=−28dB 2R 2=−63dB300 m wavelength400 km range

Atmospheric Noise Factor at HF●Noise below 30 MHz is dominated by atmosphere and man-made sourcesA) Atmospheric 99.5%tileB) Atmospheric 0.5%tileC) Man-made (Quiet)D) GalacticE) Man-made (City)At =300mF a70dBAt =100mF a50dBAt =15mF a30dBSource:ITU-R P.372-10 (2009)

InterferenceNOAA Table Mountain FacilityBoulder, ColoradoOther spectrum users often set the “noise” level

SignalS= P t G t 1 2 G r16 R 2 L p 4S= P tG tG r64 2 R 2Radar Equation for IonosondesIgnoring propagation lossesP t1 kW =60dBmG t G r 3 dBS 3810 log 10 R 2[dBm]NoiseN =k T 0 B F n F aB=15kHzF n 6 dBAt =300mF a 70dBAt =100mF a 50dBActive PreampAt =15mF a 30dBk T 0 B F n =−124 dBm

SNR Examples (20 and 3 MHz)●●●●R=100 km, λ=15m (20 MHz)● S=-38dBm ; N= -96 dBm ; SNR=+58 dB±10 dBR=400 km, λ=15m (20 MHz)● S=-50 dBm ; N=-96 dBm ; SNR=+45 dBR=100 km, λ=100m (3 MHz)● S=-22 dBm ; N= -76 dBm ; SNR=+54 dBR=400 km, λ=100m (3 MHz)● S=-34 dBm ; N= -76 dBm ; SNR=+41 dB±20 dBFor sites with “reasonable” noise,very high SNR can be obtained with “modest” antennas

SNR Example (1 MHz)●●●Antenna gains are no longer constant●●Transmit antenna is small and inefficient (-10 dBi)Receive antenna is close to the ground (-15 dBi)R=100 km, λ=300m (1 MHz)●S=-37 dBm ; N=-56 dBm ; SNR= +19 dBR=400 km, λ=300m (1 MHz)● S=-49 dBm ; N=-56 dBm ; SNR= +6 dB±30 dBEven “large” antennas become electrically small at low frequenciesInefficiencies and atmospheric noise take over.This ignores propagation loss, which is significant!

Polarization●●Ordinary and eXtraordinarypolarizations are circular and ofopposite rotation●Except very near the magneticequator, it is linearTwo orthogonal, linearly polarizedantennas can form a circularlypolarized antenna●●Digisondes do this in hardwareat the antennaVIPIR and Dynasonde do this inthe analysis softwareSan Juan, Puerto Rico

End of Section 2Questions?

VIPIR Operations

SPGR●●●●●●The virtual height of the ionosphere can bemeasured using the phase differences betweentwo closely spaced frequencies.The result is called Stationary Phase GroupRange or Precision Group HeightAssumes the actual height of reflection is constant●Can be relaxed by using multiple values of ΔfSubject to 2π ambiguitiesSubject to Doppler shifth'= c4 Range precision becomes related to phaseprecision: → 100 m f

●●●●●●Pulse SetsA pulset is a sequence of pulses at a nominalfrequency with a pattern of frequency offsetsintended to accomplish a desiredexperimental objective“Atomic”Stationary Phase Group Range (SPGR)●Precision Group HeightSpectral Analysis (i.e. FFT)Example: 8 pulse pulset for Dynasonde●+1, -3, +3, -1, -1, +3, -3 ,+1 {kHz}Controls the statistics of SPGR and Doppler

Ramps, Repeats and Ionograms●●●●A Ramp is a group of pulsets taken at asequence of nominal frequenciesRepeats are the number of times each Rampis repeated before going on to the next rampAn Ionogram is a continuous set of Ramps andRepeats which cover the entire specified set ofNominal FrequenciesThis concept is used to control the statistics ofthe observation sequence within thecoherency limitations of the ionosphere

Dynasonde Principles●Phase differences among several (4-8) pulsedsignals of a carefully designed pulse set, receivedthrough several (4-8) antenna/receiver channels,define, by a least squares solution, a radio “echo”with physical parameters:●●●●●“Doppler” or phase-path velocity V*, m/s“Stationary-Phase Group Range” R´, kmEastward XL and northward YL echolocations, kmPolarization rotation or “chirality” PP, degreesThe pulse set mean phase φ 0, degrees●●●A least-squares residual EP, degreesAn echo peak amplitude A, decibels, from signal magnitudePossible 2 nd order parameters with 8 antennas and receivers

TimeTimeTimeShuffle ModeInterleave a sweep frequency ionogram with a fixedfrequency HF radar observation on a pulse-by-pulse basisSweep Pulse 1Sweep Pulse 2Sweep Pulse 3Fixed Pulse 1Fixed Pulse 2Fixed Pulse 3Sweep Pulse N+Fixed Pulse N●●More efficient useof radar resourcesAddresses rapidscale dynamicsSweep Pulse 1Fixed Pulse 1Sweep Pulse 2Fixed Pulse 2Sweep Pulse 3Fixed Pulse 3Sweep Pulse NFixed Pulse N200GB per day!

Shuffle Mode Ionogram

Shuffle Mode Fixed Frequency

Detailed ViewResearch Opportunity

Space Shuttle Modified IonosphereModifiedIonosphereSignatureSTS-135 Trajectory300 km113 km105 kmResearch OpportunityT+04:00T+08:00

Shuttle Modified Ionosphere

VIPIR Operation●●●Operating the VIPIR radar involves editing textfiles and loading these files into the radar.●●●●●●station.txt – Site specific informationfreq_settings.txt – Frequency settingstiming.txt – Timing settingsfrequency_table.txt – Arbitrary frequency tableddc_setting.txt – Receiver filter settingsduc_settings.txt – Transmitter filter settingsThe continents of these files fill the SCTMapping between these files and SCT values isstraightforward

RIQ Data Format●VIPIR data: Raw In-phase and QuadratureSCTPCT #1Data #1PCT #2Data #2...PCT #NData #N●●●SCT: Sounding Configuration Table●●Instrument settings (output)Instrument control (input)PCT: Pulse Configuration Table●Data Block●●●●Pulse-to-pulse variable settings16 bit valuesIn-phase and Quadrature8 receiversRequested number of rangegates

Sounding Configuration Table●●Binary object used to control the radar and record the instrumentsettingsC or FORTRAN structure! Top level Sounding Configuration Table, Version 1.2!TYPE :: SCTtypeINTEGER(KIND=4) :: magic! magic number 0x51495200INTEGER(KIND=4) :: sounding_table_size ! bytes in sounder configuration structure (this file)INTEGER(KIND=4) :: pulse_table_size ! bytes in pulse configuration structureINTEGER(KIND=4) :: raw_data_size ! bytes in raw data block (one PRI)REAL(KIND=4) :: struct_version ! Format Version Number. Currently 1.2INTEGER(KIND=4) :: start_year! Start Time Elements of the ionogram (Universal Time)INTEGER(KIND=4) :: start_daynumber !INTEGER(KIND=4) :: start_month !INTEGER(KIND=4) :: start_day !INTEGER(KIND=4) :: start_hour !INTEGER(KIND=4) :: start_minute !INTEGER(KIND=4) :: start_second !INTEGER(KIND=4) :: start_epoch! epoch time of the measurement start.CHARACTER(128) :: readme! Operator comment on this measurementINTEGER(KIND=4) :: decimation_method ! If processed, 0=no process (raw data)REAL(KIND=4) :: decimation_threshold ! If processed, the threshold value for the given methodCHARACTER(128) :: user! user­definedTYPE(STATIONtype) :: station ! Station info substructureTYPE(TIMINGtype) :: timing ! Radar timing substrutureTYPE(FREQUENCYtype) :: frequency ! Frequency sweep substructureTYPE(RECEIVERtype) :: receiver ! Receiver settings substructureTYPE(EXCITERtype) :: exciter ! Exciter settings substructureTYPE(MONITORtype) :: monitor ! Built In Test values substructure

SCT StationTYPE :: STATIONtypeCHARACTER(64) :: file_id ! name of station settings fileCHARACTER( 8) :: ursi_id ! URSI standard station ID codeCHARACTER(32) :: rx_name ! Receiver Station NameREAL(KIND=4) :: rx_latitude ! Position of the Receive array reference point [degrees North]REAL(KIND=4) :: rx_longitude ! [degrees East]REAL(KIND=4) :: rx_altitude ! meters above mean sea levelINTEGER(KIND=4) :: rx_count ! Number of defined receive antennasCHARACTER(32),DIMENSION(32) :: rx_antenna_type ! Rx antenna type text descriptorsREAL(KIND=4),DIMENSION(3,32) :: rx_position ! X,Y,Z = (East,North,Up) Positon [m] of each RxREAL(KIND=4),DIMENSION(3,32) :: rx_direction ! X,Y,Z = (East,North,Up) Direction of each RxREAL(KIND=4),DIMENSION(32) :: rx_height ! Height above ground [m]REAL(KIND=4),DIMENSION(32) :: rx_cable_length ! physical length of receive cables [m]REAL(KIND=4) :: frontend_atten ! Front End attenuator settingCHARACTER(32) :: tx_name ! Transmitter Station NameREAL(KIND=4) :: tx_latitude ! Position of the Transmit Antenna reference point [degrees North]REAL(KIND=4) :: tx_longitude ! [degrees East]REAL(KIND=4) :: tx_altitude ! meters above mean sea levelCHARACTER(32) :: tx_antenna_type ! Tx antenna type text descriptorsREAL(KIND=4),DIMENSION(3) :: tx_vector ! tx antenna direction vector [m]REAL(KIND=4) :: tx_height ! antenna height above reference ground [m]REAL(KIND=4) :: tx_cable_length ! physical length of transmit cables [m]INTEGER(KIND=4) :: drive_band_count ! Number of antenna drive bandsREAL(KIND=4),DIMENSION(2,64) :: drive_band_bounds ! drive bands start/stop in kHzREAL(KIND=4),DIMENSION(64) :: drive_band_atten ! antenna drive atteunuation in dBINTEGER(KIND=4) :: rf_control ! ­1 = none, 0 = drive/quiet, 1 = full, 2 = only quiet, 3 = only attenCHARACTER(32) :: ref_type ! Type of reference oscillatorCHARACTER(32) :: clock_type ! Source of absoulte UT timingCHARACTER(128) :: user! Spare space for user­defined informationEND TYPE STATIONtype

SCT Timing! Timing of the measurementTYPE :: TIMINGtype ! Time values are in microseonds unless otherwise indicatedCHARACTER(64) :: file_id ! Name of the timing settings fileREAL(KIND=4) :: pri ! Pulse Repetition Interval (PRI) (microseconds)INTEGER(KIND=4) :: pri_count! number of PRI's in the measurementINTEGER(KIND=4) :: ionogram_count ! repeat count for ionogram within same data fileREAL(KIND=4) :: holdoff ! time between GPS 1 pps and startREAL(KIND=4) :: range_gate_offset ! true range to gate 0INTEGER(KIND=4) :: gate_count ! Number of range gates, adjusted up for USB blocksREAL(KIND=4) :: gate_start ! start gate placement [us], adjustedREAL(KIND=4) :: gate_end ! end gate placement [us], adjustedREAL(KIND=4) :: gate_step ! range delta [us]REAL(KIND=4) :: data_start ! data range placement start [us]REAL(KIND=4) :: data_width ! data pulse baud width [us]INTEGER(KIND=4) :: data_baud_count ! data pulse baud countCHARACTER(64) :: data_wave_file ! data baud pattern file nameCOMPLEX(KIND=4),DIMENSION(1024) :: data_baud ! data waveform baud patternINTEGER(KIND=4) :: data_pairs ! number of IQ pairs in waveform memoryREAL(KIND=4) :: cal_start ! cal range placement start [us]REAL(KIND=4) :: cal_width ! cal pulse baud width [us]INTEGER(KIND=4) :: cal_baud_count ! cal pulse baud countCHARACTER(64) :: cal_wave_file ! alternative baud pattern file nameCOMPLEX(KIND=4),DIMENSION(1024) :: cal_baud ! cal waveform baud patternINTEGER(KIND=4) :: cal_pairs ! number of IQ pairs in waveform memoryCHARACTER(128) :: user! Spare space for user­defined informationEND TYPE TIMINGtype!

SCT FrequencyTYPE :: FREQUENCYtype ! Values are in kilohertz unless otherwise indicatedCHARACTER(64) :: file_id ! Frequency settings fileREAL(KIND=4) :: base_start ! Initial base frequencyREAL(KIND=4) :: base_end ! Final base frequencyINTEGER(KIND=4):: base_steps ! Number of base frequenciesINTEGER(KIND=4):: tune_type ! Tuning type flag: 1=log, 2=linear, 3=table, 4=ShuffleModeREAL(KIND=4),DIMENSION(8192) :: base_table ! Nominal or Base frequency tableREAL(KIND=4) :: linear_step ! Linear frequency step [kHz]REAL(KIND=4) :: log_step ! Log frequency step, [percent]CHARACTER(64) :: freq_table_id ! Manual tuning table filenameINTEGER(KIND=4):: tune_steps ! all frequencies pre­ramp repeatsINTEGER(KIND=4):: pulse_count ! pulset frequency vector lengthINTEGER(KIND=4),DIMENSION(256) :: pulse_pattern ! pulset frequency vectorREAL(KIND=4) :: pulse_offset ! pulset offset [kHz]INTEGER(KIND=4):: ramp_steps ! pulsets per B­mode ramp (ramp length,base freqs per B­block)INTEGER(KIND=4):: ramp_repeats ! repeat count of B­mode rampsREAL(KIND=4),DIMENSION(8192):: drive_table ! base frequencies attenuation/silent tableCHARACTER(128) :: user! Spare space for user­defined informationEND TYPE FREQUENCYtype

SCT Receiver and Exciter! Receiver SettingsTYPE :: RECEIVERtypeCHARACTER(64) :: file_id ! Frequency settings fileINTEGER(KIND=4) :: rx_chan ! Number of receiversINTEGER(KIND=4),DIMENSION(16) :: rx_map ! receiver­to­antenna mappingINTEGER(KIND=4) :: word_format ! 0=big endian fixed, 1=little endian, 2=floating_pointINTEGER(KIND=4) :: cic2_dec ! DDC filter blockINTEGER(KIND=4) :: cic2_interp ! DDC filter blockINTEGER(KIND=4) :: cic2_scale ! DDC filter blockINTEGER(KIND=4) :: cic5_dec ! DDC filter blockINTEGER(KIND=4) :: cic5_scale ! DDC filter blockCHARACTER(32) :: rcf_type ! text descriptor of FIR filter blockINTEGER(KIND=4) :: rcf_dec ! decimation factor for FIR filter blockINTEGER(KIND=4) :: rcf_taps ! number of taps in FIR filter blockINTEGER(KIND=4), DIMENSION(160) :: coefficients ! Receiver filter coefficientsREAL(KIND=4) :: analog_delay ! analog delay of receiver, usCHARACTER(128) :: user! Spare space for user­defined informationEND TYPE RECEIVERtype!! Exciter SettingsTYPE :: EXCITERtypeCHARACTER(64) :: file_id ! Frequency settings fileINTEGER(KIND=4) :: cic_scale ! DUC filter blockINTEGER(KIND=4) :: cic2_dec ! DUC filter blockINTEGER(KIND=4) :: cic2_interp ! DUC filter blockINTEGER(KIND=4) :: cic5_interp ! DUC filter blockCHARACTER(32) :: rcf_type ! text descriptor of FIR filter blockINTEGER(KIND=4) :: rcf_taps ! number of taps in FIR filter blockINTEGER(KIND=4) :: rcf_taps_phase ! number of taps in FIR filter blockINTEGER(KIND=4), DIMENSION(256) :: coefficients ! Receiver filter coefficientsREAL(KIND=4) :: analog_delay ! analog delay of exciter/transmitter, usCHARACTER(128) :: user! Spare space for user­defined informationEND TYPE EXCITERtype

SCT monitor and PCT! System status and Built­In­Test infoTYPE :: MONITORtypeINTEGER(KIND=4),DIMENSION(8) :: balun_currents ! As read prior to ionogramINTEGER(KIND=4),DIMENSION(8) :: balun_status ! As read prior to ionogramINTEGER(KIND=4),DIMENSION(8) :: front_end_status! As read prior to ionogramINTEGER(KIND=4),DIMENSION(8) :: receiver_status ! As read prior to ionogramINTEGER(KIND=4),DIMENSION(2) :: exciter_status ! As read prior to ionogramCHARACTER(512) :: user! Spare space for user­defined informationEND TYPE MONITORtype! Pulse Configuration Table Version 1.2TYPE :: PCTtypeINTEGER(KIND=4) :: record_id! Sequence number of this PCTREAL(KIND=8) :: pri_ut ! UT of this pulseREAL(KIND=8) :: pri_time_offset ! Time read from system clock, not precise.INTEGER(KIND=4) :: base_id! Base Frequency counterINTEGER(KIND=4) :: pulse_id! pulse set element for this PRIINTEGER(KIND=4) :: ramp_id! ramp set element for this PRIINTEGER(KIND=4) :: repeat_id! ramp repeat element for this PRIINTEGER(KIND=4) :: loop_id! Outer loop element for this PRIREAL(KIND=4) :: frequency ! Frequency of observation (kHz)INTEGER(KIND=4) :: nco_tune_word ! Tuning word sent to the receiverREAL(KIND=4) :: drive_attenuation ! Low­level drive attenuation [dB]INTEGER(KIND=4) :: pa_flags! Status flags from amplifierREAL(KIND=4) :: pa_forward_power ! Forward power from amplifierREAL(KIND=4) :: pa_reflected_power ! Reflected power from amplifierREAL(KIND=4) :: pa_vswr ! Voltage Standing Wave Ratio from amplifierREAL(KIND=4) :: pa_temperature ! Amplifier temperatureINTEGER(KIND=4) :: proc_range_count ! Number of range gates kept this PRIREAL(KIND=4) :: proc_noise_level ! Estimated noise level for this PRICHARACTER(64) :: user ! Spare space for user­defined informationEND TYPE PCTtype

Floating Point Output● Digital Down-converter AD6624 has internal 24bit RAM Coefficient Filter (RCF)● USB2 interface limits raw data to 16 bits per I/Qsample● Current software reports 16 bit signed integer● Floating point mode is tested●●12 bit mantissa + 4 bit exponentIncreases Theoretical dynamic range from90dB to 138dB●●Better noise observationsImproves strong interference tolerance

RCF Mapping23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 14 6 13 5 12 4 11 3 14 2 13 1 12 024 bit RCFxxx x x15 14 13 12 11 10 9 8 7 14 6 13 5 12 4 11 3 14 2 13 1 12 0x x x16 Bit FixedM11 M10 M9 M8 M7 M6 M5 M4 M3 M2 14 M1 13 M0 12 E3 11 E2 14 E1 13 E0 1212+4 Floating Point

Large Signal TestsInternal noise is +10 dBPeak signals are +105 dBLinear range +5 to +105 dBMinimum signal is -10 dBNoise is not severelyquantized

End of Section 3Questions?

Preamp Calibration

Phase Calibration●●●●●Internal calibration signal is inserted into the farend of each receive cable or receiver preamplifierwith a common cableFirst performed at San Juan with Dr. Zabotin●●Discovered DC bias problemDiscovered and Repaired Receiver ImpedanceproblemReceive cables trimmed to match phase response.Wallops: Phase error < 1º at 20 MHzTo Do●●Apply to BoulderRe-visit San Juan

San Juan upgrade and calibrationApril 2013San Juan, Puerto Rico

Wallops Rx Cables: Before

Wallops Rx Cables: After

●Total Field CalibrationTotal calibration of all 8 receive antennas#3 and #6 are outliers above 18 MHzWallops fieldcalibration data showphase differenceswithin +/- 2 degrees upto 17 MHz.●F region traces are notoften observed above~12 MHz.

●●DC bias in Calibration CircuitPreamplifier DC return current through calibrationcircuit saturated the RF signal splitters.Installing DC blocks resolved the issue.

●Temperature Sensitivity of Rx CablesWallops calibrations showed strong variability● Temperature is suspectedWallops cal data forthe same Rx twinaxcable at three differenttimes relative to a 4thmeasurement.Lab measurementshave confirmed thistemperature response.Electrical lengthchange is -0.0026%per ºCCalibration objectivesare ~ 0.007%Some options arebeing considered

Free VIPIR Software●riq-ionogram - Terry Bullett●●FORTRAN-95 Linux Version 2.07 in developmentOperational code for plots and NetCDF●Plot-VIPR – Dick Grubb●●●Matlab program to make imagesGet_data_simple – Dick Grubb●Matlab read subroutine, for teachingriq_idl – Justin Mabie●IDL raw data reader, for teachingftp://ftp.ngdc.noaa.gov/ionosonde/software/VIPIR/

VIPIR FacilitiesCurrent (13)Planned (9)Updated June 2013

Science and Engineering Needs●●●●●●●●●●Improved dynamic range → 16 bit ADCGreater data bandwidth → USB3More Digital FiltersManual Ionogram Analysis SoftwareEcho Detection and ParametrizationImproved Ionogram ScalingAmplitude and Phase CalibrationsImproved data collection → continuousSuper-resolution direction finding & plasma imagingInterference removal

Internet Resources●●World Data Center A, Boulder:http://www.ngdc.noaa.gov/stp/IONO/ionohome.htmlDigisondes and ARTIST : http://ulcar.uml.edu/●Autoscala: http://roma2.rm.ingv.it/en/facilities/software/18/autoscala●●●●●●●●ESIR : http://www.spacenv.com/Dynasonde21: Bill.Wrightster@gmail.comLow-latitude Ionospheric Sensing System: http://jro.igp.gob.pe/lisn/Vertical Incidence Pulsed Ionosphere Radar (VIPIR): Terry.Bullett@noaa.govCanadian Advanced Digital Ionosonde (CADI): http://cadiweb.physics.uwo.ca/Ionospheric Prediction Services (IPS): http://www.ips.gov.au/Ionosonde Network Advisory Group (INAG)http://www.ips.gov.au/IPSHosted/INAG/SPIDR: http://spidr.ngdc.noaa.gov/spidr/index.jsp

Credits●●●●●●●●●●●●●Jicamarca Radio ObservatoryKorean Polar Research InstituteNICT, JapanNational Central University, TaiwanNOAA National Geophysical Data CenterNASA Wallops Island Flight FacilityUS Geological SurveyUS Air Force Research LaboratoryINGV, ItalyIPS, AustraliaBoston CollegeScion AssociatesAll ionosonde data producers who freely share their data!