Electromagnetic Waves in Near-Earth Space

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1

SCPNT Symposium

November 7, 2007

Systems Technology for Remote

Sensing of Near-Earth Space

Umran S InanProfessor of Electrical Engineering

Director, Space, Telecommunications and Radioscience (STAR)

Laboratory

Electrical Engineering Department

Stanford University, Stanford, California 94305

http://www-star.stanford.edu/~vlf/



2

Very Low Frequency (VLF) Group

Largest group within Space, Telecommunications &

Radioscience (STAR) Lab, one of five EE Labs

VLF Group Personnel

3 Senior Research Associates, 3 Research Associates

Several active Emeriti & Consulting Professors

1 to 2 full-time engineers, 1 Data Aide

Currently 26 MS/PhD Students, graduated 27 PhDs since 1990

Experimental & theoretical research on waves & energetic

particles in near-Earth space, ionosphere, radiation belts, very

low frequency remote sensing, lightning discharges & high

altitude effects, such as sprites, elves Design & construction of sensitive receivers and autonomous

systems, deployed worldwide



3

Electromagnetic Waves in

Near-Earth Space



4

Electromagnetic Waves in

Near-Earth Space



5

Electromagnetic Emissions in

Near-Earth Space



6

Stanford at Palmer & South Pole

Stations, Antarctica



7

Lightning-generated

Whistlers

Very Low Frequency (VLF)waves launched by lightningpropagate in the Earth-ionospherewaveguide (v p=c )

Wave energy also couplesupward to the radiationbelts, propagating along

filamentary “ducts” of enhanced ionization

The magnetospheric plasmais a dispersive slow wavemedium (v p=0.01 c )

Signal arriving at theconjugate region sounds like

a “whistler”



8

Lightning-induced Electron

Precipitation (LEP) on DEMETER

LEP bursts on DEMETER.(top to bottom) (left)Broadband VLF data and(right) narrowband VLF datafrom ground stationsshowing sferics caused bylightning strokes;

Spectrograms of electricfield from ICE onDEMETER showing 0+whistlers from the samelightning strokes;

Electron spectra from IDPon DEMETER showing bursts of precipitated

electrons; integral flux (99.6to 304.3 keV).

The map shows thetrajectories of DEMETER satellite; blue and greenrespectively for the cases onthe left and right.

GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L07103, doi:10.1029/2006GL029238, 2007



9

Lightning-induced Electron

Precipitation (LEP)



10

Subionospheric VLF Remote

Sensing

Many VLF

transmitters operate

worldwide, providing

a range of coherentlaser-like signals

with which to probe

the ionospheric

regions through

which they

propagate



11

Measurement: Simple Receivers

Allow Continuous Monitoring

VLF receivers at 13 high schools

Provides excellent opportunities for outreach



12

Non-ducted LEP Events

(a)

(b)

(c)

(d)

In general whistler

waves propagate in

non-ducted mode,

illuminating large

regions of the

radiation

In each event, onsetdelay ( t)an onset

duration (t d) are

measurable,corresponding to

wave/particle travel

times and duration

of LEP pulse



13

Subionospheric VLF Signatures

of LEP Events: Spatial Extent

Dashed line VLF paths perturbed;solid line ones are not; theoretical

precipitation region superposed

VLF Amplitude Data for 24 March 2001

Full extent of the ionospheric

disturbance produced by an LEP burst

(due to a single flash) is captured

Corresponding region of the inner

radiation belt is affected by whistler

waves from a single lightning flash



14

Theoretical Modeling

Peter and Inan [2006]



15

Stanford VLF Receivers(sun never sets on Stanford VLF )

Transmitter at Pole(7-km antenna)

Palmer Station

Antarctica

Line Receiver

Preamp

Antenna



16

IHY/UNBSS Program



17

Antarctic Unmanned Receivers

Single-chip LNA



18

ELF/VLF Applications with HAARP

100 km

ELF / VLFRadio Waves

60 km

Detect Submarine

Comm Submarine Imaging Buried TargetsComm Buried Receiver

Control of Charged ParticleEffects on Satellite Operations

HAARP HFTransmitter





19

High-Frequency Active Auroral

Research Program (HAARP)



20

HAARP VLF Signals at Chistochina,Alaska (~30 km from HAARP)



21

Natural and HAARP-

injected ELF/VLF Signals



22

Whistlers, Auroral Hiss and

HAARP ELF/VLF Signals



23

Very Strong HAARP

ELF/VLF Signals



24

Amplified Signals and TriggeredEmissions on Tangaroa & Alaska



25

Multiple Traverses

Between Hemispheres



26

ELF/VLF Wave-InjectionExperiments with HAARP



27

Quickly Developing Storm Systems

Feet



28

Stanford VLF Buoy in NewZealand: Integration & Launch



29

HAARP VLF Buoy in

Construction



30

Buoy Electronics Integration



31

Stanford VLF Buoy at Sea



32

Stanford VLF Buoy at Sea andback in New Zealand



33

Photos



34

Photos



35

Systems Overview

ChargeController

Solar Panels

Batteries

Electronics Package

Preamp

Loop Antennas

IRIDIUMs

Antennas

ARGOS

GPS



36

Main Electronics

IRIDIUM

Interface

VLF Filter

Power

Filtering/Housekeeping

IRIDIUMInterface

Main

Atmel

GPS

IRIDIUM Atmel

IRIDIUM Atmel

DSP

ADC

Data Bus

Main Power Bus

IRIDIUM Serial Data

GPS Serial Data

IRIDIUM Power

VLF Filter Power

CF



37

Motherboard, DSP. ADC, CF &

Iridium Interfaces

Motherboard

• ATMega128 Main Controller

• 100Mhz Bus interface for all subsystems

• 100khz Sample Clock Generation

• ATMega128 Iridium controllers

DSP TI TMS320C6711 DSP

• 150 MHz, 100MHz bus

• Floating point capabilities

• 64MB Ram

• Onboard FPGA

ADC

• 3 Channels

• 16 Bit ADC, up to 200Khz sampling

• 512 deep 18bit FIFO buffers

• CPLD

• Bus interface controller

• ADC Controller

CF Interface

• Direct interface to Compact Flash –

full throughput• Stackable design

• Max 15 per memory space

• Subject to bus signal integrity

Iridium Interface

• Iridium Modem brick interface

• Rx/Tx Indicators

• Optically isolated from main system



38

GPS, Line Receiver,

Housekeeping/power, & AAF

GPS• Low Power Motorola

• Battery Backup

• 1PPS Generation

Line Receiver

• Three differential channel

• Selective Gain (0,2,5,10,20dB)

• 8th Order Min-Q Elliptic Filter

Housekeeping/Power

• Switching 5V, 12V regulators

• Housekeeping filter and ADC

• Reset Circuitry

• Modem Power Controls

• Power Indicators



39

Buoy 1.5 Hardware Stack

Pic needed



40

Buoy 1.5 Hardware Stack



41

Stack In Mumetal Can



42

Charger Section

Solar

PanelSwitch

Charge

Control

Battery Battery

Battery Battery

External Power

14.45VSystem

x4Battery



43

Buoy 1.5 Power Box



44

Iridium Enhancements

Performed a study in May 2005 on colocated Iridium terminals

Interference and blanking detected at 3’ separation

Rooftop antenna array created to minimize interference and maximize horizon

exposure





46

Roof Testing



47

Roof Testing



48

HAARP VLF Buoy 2.0



49

Stanford Buoys Launched

from the Tangaroa



50

Deployment of Buoy



51



52

Amplified ELF Signals on the

HAARP Stanford Buoy



53

15 dB/s Amplification & Triggered

Emissions



54

Transmitter-Induced Precipitationof Electron Radiation (TIPER)



55

VLF Receiver at Kwajalein Atoll



56

VLF Receiver at Waimea High

School, Kauai



57

Stanford System at Midway Atoll



58

Tern Island Autonomous System



59

VLF Data from Tern Island

F r e q u e n c y ( k

H z )

10

20

30

40

Time (sec)1 2 3 4

VLF Transmitters

Radio Impulses

from Lightning

Unprecedented low

levels of ‘hum’

40

60

80

d B



60

Transmitter-Induced Precipitationof Electron Radiation (TIPER)

Use subionospheric VLF

method (used for

detection of lightning

induced precipitation) to

observe transmitter

induced precipitation

D Layer

Ionosphere

Precipitating charged particles

modify ionosphere electron density

Diagnostic VLF

Transmitters

Diagnostic VLF

Receivers

Precipitation

Magnetic field lineEscaped VLF

waves from

lightning strikes

or powerful VLF

transmitter

e- e- e-

Signal Perturbation V L F a m p l i t u d e

Time

Powerful

VLF Xmtr



61

Subionospheric VLF Detection of NPM-induced Precipitation

TIPER M ith Th ti ll



62

TIPER Map with Theoretically

Determined Precipitation Region

Figure 1 of Inan et al. [2006] (in review at GRL)

Ob ti f NPM i d d



63

Observations of NPM-induced

Precipitation on NLK & NLM


NPM i d d P i it ti



64

NPM-induced Precipitation:

Model & Data Comparison




65

Mission Payload: Particle Detector

Energetic Electron Detector Pattern after successful

DEMETER mission

French sat

High geometric factor

High-time resolution

1.2 cm2.ster Maximum

geometrical

factor

0.07-0.7(2.5) MeV

256 channels

Energy range

895 mWPower

525 gMass

6 mFoil for p+ andh rejection

2 mm AlExternal

shielding

Implanted SiS = 490 mm2 ( 25 mm)

Detector



66

NPM-induced ElectronPrecipitation on DEMETER

NPM

NWC i d d P i it ti



67

NWC-induced Precipitation on

DEMETER [from Sauvaud et al .]



68

TIPER Optical Measurements

Current Plan for NWC



69

Current Plan for NWC

Keying Experiments



70

Wave-Particle Interactions &Radiation Belts

Wave

Generation

Wave

Propagation

Wave-Particle

Interaction

O Hi h Altit d N l D t ti



High-altitude nuclear tests of 1958 and 1962 demonstrated wide-areaeffects with significant military impacts for numerous systems.

Radars: Blackout, absorption, noise, clutter, scintillation

Communications: Blackout, scintillation fading, noise, connectivity

Optical Sensors: IR, Visible, UV backgrounds, clutter; noise

Satellites: Trapped radiation; radiation damage to electronics

Electronics & Power: Electromagnetic pulse; electrical systems damage

STARFISH

1.4 MT at 400 km

ORANGE

3.8 MT at 43 km

KINGFISH

__ MT at __ km

TEAK

3.8 MT at 76.8 km

CHECKMATE

__ MT at __ km

One High Altitude Nuclear Detonation

Impacts Multiple Systems

From Defense Threat Reduction Agency/Mission Research Corp briefing, 15 Jan 2003



72

How Could It Happen?

Collateral damage from regional nuclear war or TMD/NMD intercept:

Nuclear warning shot in a regional conflict;

Effort to damage adversary forces/infrastructure with

electromagnetic pulse;

Detonation of salvage-fused warhead upon

exoatmospheric intercept attempt.

Deliberate effort to cause economic damage with

lower likelihood of nuclear retaliation:

By rogue state facing economic strangulation or

imminent military defeat;

Pose economic threat to the industrial world withoutcausing human casualties or visible damage to economic

infrastructure.

Senior Pakistani officials have said that

Pakistan's nuclear warheads have

undergone shock and vibration tests and

are ready to be mounted on the country's

Ghauri, or Hatf V, intermediate-range

ballistic missile.

JANE'S DEFENCE WEEKLY

- 3rd JUNE 1998

R di ti B lt R di ti



73

Radiation Belt RemediationWhat is the problem?

Remediation can: Accelerate the natural decay of trapped

particles in narrow HAND region

Save critical LEO space missions

Enable environment for replenishment within

30 days

HAND Belt

50 kT, 31.3 deg, 75.2 deg, 200km

Nuclear vs Natural Environment (~800km Polar Orbit)

1E+0

1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

1 14 30 365Days

D o s e ( R a d s S i )

Nuclear

Natural

High Altitude Nuclear Detonation produces huge increase in radiation for satellites – all LEO s/c fail within months

0.1 1.0 10

40

30

20

10

Months After Burst

30 Krad (Si)

Bay of Bengal50 kT burst

At 250 km100 mil Al

N u m b e r

o f A s s e t s

R e m

a i n i n g

1.5 MeVElectron Flux

Defense Threat Reduction

Agency

Radiation Belt Remediation



FOUOTenfold increase in particle removal rate requires ~ 17kW => a few

satellites!

ELF/VLF Waves Control Particle Lifetimes

L shell = distance/RE

Radiation Belt RemediationParticle Dynamics

Particles mirroring below100 km are “lost”

Electromagnetic

wave

Pitch-angle

To remove particles the magnitude of the velocity need not be changed - just the

angle between the velocity and magnetic field!

Radiation Belt Remediation



75

Radiation Belt RemediationKey Processes

VLF wave

generation

Wave propagation

Wave-particle

interaction

Wave-particle scattering

• Are interactions diffusive or coherent?

• Can tailored wave forms improve efficiency?

Global wave propagation and amplification

• Where does wave power go in the far field?

• Can waves be amplified through plasma

processes?

ELF-VLF wave injection efficiency

• Can ground-based antennas radiate VLF

efficiently through the ionosphere?

• Can space-based antennas radiate VLF into the

far-field at high power levels?

Scientific

UnderstandingIonosphere

Outer-zone electrons

HAND belt electrons



76

DSX / WIPER Spacecraft Mission

WIPER: Wave-Induced Precipitation of Electron Radiation

i) Characterize naturally occurring VLF signalsa. In the inner radiation belt

b. Slot region

c. Inner edge of the outer belt.

iii) Quantify pitch angle scattering a. Energetic electrons by

whistler-mode waves

b. Naturally occurring

or injected.

ii) In-situ injection of VLF waves a. Efficiency in injection

b. Propagation characteristics

c. Effect on energetic particles

Active and Passive Observation Objectives

DSX Spacecraft



77

WIPER Block Diagram

LVDS

Receiver sensitivity vs frequency

IMAGE Spacecraft Instrument Deck

RPI

TATU

TATU

TATU

TATU

TCU



78

WIPER Block Diagram

LVDS

Anti-aliasing filter

Low-noise amplifier

Op-amps

Capacitors

Transconductor

Test Circuitry Functional Circuitry

S t a g e

0

S t a g e 1

S t a g e 2

S t a g e 3

S t a g e 4(a)

(b)

PARX ADC Die Layout

Low Noise Amplifier

Silicon Germanium 0.25 m BiCMOS

Flat gain over 5 decades in frequency

Negligible flicker noise <100 Hz

>100 dB SFDR

Responds to Tens of nV (NF 2-5 dB)





80

15 cm

20 cm

R e c e i v e r S l i c e s

P o w e r a n d

C o m m B o a r d

15 cm

P r e a m p

BBR Physical Dimensions

Components 5 receiver boards

Y Antenna (Electric FieldDipole)

Z Antenna (Electric FieldDipole)

Bx (Searchcoil)

By (Searchcoil)

Bz (Searchcoil)

1 preamp board

Z Antenna

1 combination power board and

communications board DC to DC converters,

RS422, and LVDS links.

BBR Commanded bySoftware Receiver (SRX)code running in theExperiment Control

System (ECS) as an

Physical Integration of BBR into



81

Physical Integration of BBR into

DSX

TASC

WIPER

TCU

VLF BBR

RECEIVER

2X TATU

X: 517 mm

Y: 133 mm

Z: 288 mm

X: 204mm

Y: 206mm

Z: 295mm

X: 300 mm

Y: 300 mm

Z: 300 mm

X: 200mm

Y: 150mm

Z: 150mm

CAD model courtesy Microsat Systems

TASC

WIPER

TCU

VLF BBR

RECEIVER

2X TATU

X: 517 mm

Y: 133 mm

Z: 288 mm

X: 204mm

Y: 206mm

Z: 295mm

X: 300 mm

Y: 300 mm

Z: 300 mm

X: 200mm

Y: 150mm

Z: 150mm

TASC

WIPER

TCU

VLF BBR

RECEIVER

2X TATU

X: 517 mm

Y: 133 mm

Z: 288 mm

X: 204mm

Y: 206mm

Z: 295mm

X: 300 mm

Y: 300 mm

Z: 300 mm

X: 200mm

Y: 150mm

Z: 150mm

CAD model courtesy Microsat Systems

Main BBR Functional



82

Main BBR Functional

Requirements

BBR shall measure the electric fieldfrom 100 Hz to 50 kHz and at highsensitivity (~1×10-16 (V/m)2 /Hz) with 16-bits of quantization

BBR shall measure the magnetic fieldfrom 100 Hz to 50 kHz and at highsensitivity (~1×-11 nT2 /Hz) with 16-bitsof quantization

BBR shall have a minimum SpuriousFree Dynamic Range of 100dB for allchannels Measured at 1.0 kHz for the Electric Field

channels

Measured at 7.0 kHz for the Magnetic Fieldchannels

BBR SFDR Measurement (Using



83

BBR SFDR Measurement (Using

DS360)

Receiver Response Preamp Response

Fundamental Tone Scaled to 0 dB



84

System Architecture

Electricdipole

antenna

AAF FPGA

To On-board

Computer or

TelemetryLNA

Preamplifier ASIC

ADC

ADC ASIC

LNA Key Specifications

Adjustable Gain

Bandwidth

Input-referred Noise

Input ImpedanceSFDR

Power

0-20 dB

100 Hz - 1 MHz

10 nV/m/Hz1/2

1 Gohm || 100 fF100 dB

5 mW

ADC Key Specifications

ResolutionSampling Rate

SFDR

Power

13 bits5 MS/s

100 dB

75 mW

AAF Key Specifications

Architecture

Adjustable 3-dB Bandwidth

Stopband Attenuation

SFDR

Power

6th-order Chebyshev (Type I)

30 kHz, 180 kHz, 1080 kHz

-80 dB (3*f c), -96dB (4*f c)

100 dB

70 mW

Fig. 1 Plasma wave receiver block diagram.

LNA M d R l



85

LNA Measured Results

Feedback is well-suited to this application

Linearity Feedback increases linear operating range Reducing gain is worthwhile trade-off Fidelity by reducing sensitivity to active devices

Programmable Gain

Feedback trades gain for bandwidth

Reduce low-frequency closed-loop gain is tolerable

Passive feedback allows gain programming without

power penaltyRadiation Tolerance

Feedback reduces gain sensitivity & improves hardness

Use of multiple series-series feedback loops

Prototype LNA performance

Flat passband gain over many gain settings in 3dB steps

Negligible flicker noise under 100 Hz

Further characterizations (SFDR) underway

LNA chip.

Fig. 3 Measured gain (upper) and input-referred noise power

spectral density (lower) for LNA.

Total Integrated Dose (TID) Test



86

Total Integrated Dose (TID) Test

Results

Gain vs Dose No change < 100kHz

Measurement noise

At 2000krad -1dB at 1MHz

f -3dB drops by 22%

LNA irradiation biasing

Maximum gain setting (20dB)

Powered (all biasing nominal)

Power vs Dose Decreases with dose

Occurs by design

Conservative pMOSbiasing scheme

At 2000krad

Pmax drops by 7.1%

Irradiation in Co-60 chamber

High dose rate: 75rad(SiGe)/s

Log steps (1/2/5) up to 2000krad

Fig. 6 Bode response (upper) and power dissipation (lower) versus dose

Single-Event Effects (SEE) Test



87

Single Event Effects (SEE) Test

Results

Illumination with mode-locked dye laser

Stimulates charge-pair production in substrate

Pico-second pulse width (tw); Variable intensity (Io)

Variable spot sizes ( o) on the order of 2-10 m2

Latch-up immunity

Scan entire die (I/O & core)

No latch-up detected over range of beam Io and o

Single-event transients

No supply glitches detected No saturation or oscillation

Signal transient ‘hot-spots’

< 2 s avg. recovery time

Measured Vdd , Out+, and Out- laser-induced SEE transients

Sample laser spot cross-section

Negative

output

Scaled

version of

supply

Positive

output

D i T h i ADC



88

Design Techniques: ADC

Design PARXADC is a digitally calibrated, pipelined analog-to-digital converter for

capturing plasma wave signals in satellite applications. It leverages thespectrographic nature of such analysis to deliver high fidelity at low power.

Key Specifications Effective Number of Bits 13

Spurious-Free Dynamic Range 100 dB Averaging of circuit and quantization noise over FFT bins allows reduction of

number of bits and hence the power dissipation. Number of bits chosen tomaintain 100dB SFDR, assuming a 20000 point FFT (4ms at 5MS/s).

Nyquist/Sampling Rate 5 MS/s Input signal bandwidth of 100 Hz – 1 MHz. Converter samples faster than Nyquist

to accommodate analog anti-aliasing filter transition bandwidth.

Power Dissipation (analog portion) < 60 mW Power Supply Voltage 2.5V

Maximum Input Signal ±1.0V fully differential

Radiation Tolerance > 100krad total dose

ADC I l t ti



89

ADC Implementation

Converter composed of twoparts: the PARXADC integratedcircuit and an Actel A54SX32AFPGA Actel FPGA houses calibration

engine, performs reconstruction, anddefines output interface

Calibration Calibration corrects DAC errors in

pipeline converter, linearizing theconversion

Feedforward (inherently stable) andfully digital (no analog trimmingfeedback loops)

Re-calibration can be initiated at anytime

May compensate for radiation induced

circuit degradation

Integrated Circuit Design Incorporates radiation hardness of

design techniques Enclosed layout transistor switches,

latchup prevention layout methods

Actel

A54SX32A

FPGA

R E C O N S T R U C T I O N

A L G O R I T H M

C A L I B R A T I O N

E N G I N E

OUTPUT

DRIVER

STAGE 7

STAGE 6

STAGE 5

STAGE 4

STAGE 3

STAGE 2

STAGE 1

TRACK AND

HOLD

CLOCK

VREFP

VREFN

ANALOGINPUT

PARXADC

Integrated Circuit

OD

RESET

PRESET

DOUT[15:0]

CALIB

DAV

calibrationcoefficients

Fig. 1. Functional diagram of PARXADC converter implementation.

ADC St t



90

ADC Status

First version tested Complete system, composed of

PARXADC silicon and Actel FPGA,operates at 2MS/s.

Performance characterization isunderway.

Second version fabricated

Returned mid-2005 Expanded calibration

Corrects gain error as well as DACerrors.

Additional breakout sections for radiation characterization of constituent functional blocks.

Radiation Tests underway

Fig. 2. Reconstructed output from PARXADC converter functioning on PARXADC (version 1) Test Board in time and

frequency domains (under 1024-pt FFT). Actel FPGA running

UINT code (Rev.04) performs reconstruction; output is shown

after calibration. Data is captured directly by logic analyzer.

Converter operating at 2MS/s with 50kHz, 500mV amplitude

input sinusoid transformer coupled.

ADC Di L t PARXADCV2



91

ADC Die Layout, PARXADCV2

Fig. 3. PARXADCV2 (PARXADC, version 2) die layout. Taped out July 2005. Total silicon dimensions 3.5mm by 3.5mm.

operational

amplifier analog

biasing breakout

for radiation

testing

operational

amplifier (from

track and holdstage) breakout

for radiation

testing

8-level flash

(from stages #1,

2, and 3) breakout for

radiation testingselect enclosed

terminal device

breakouts for

radiation testing

6-stage pipelined

analog-to-digital

converter with

dedicated track

and hold stage

N S f d C SCPNT



92

New Stanford Center: SCPNT

Stanford Center for Position Navigation and Time(SCPNT) http://scpnt.stanford.edu/

Formed by faculty from EE, AA, Physics Per Enge (AA), Director

U. Inan (EE) and M. Kasevich (Phys), Vice-Directors

Centimeter accuracy anywhere, anytime

Research includes new signals (e.g., GPS, Galileo),integrated sensors, inertial & atomic clock technologies,directional antennas & signal processing, atmospheric &orbital science

Funded by industry & government Provides basis for new faculty appointments



The End

Documents

Electromagnetic Waves in Near-Earth Space