the demonstrations & science experiment...

Gregory Ginet, MIT/LL

Michael Starks, AFRL

Bob Johnston, AFRL

Jay Albert, AFRL

The Demonstrations & Science

Experiment (DSX)

Radiation Belt Storm Probes

Science Working Group

31 Aug 2010

PROPULSION

DIRECTORATE

Space Environmental

Effects

VLF Wave-Particle Interaction

Experiment

Space Weather

Experiments

Spacecraft Bus

Launch SegmentProgram Office

Systems Engineering

Integration and Test

DSX The Team

DSX Outline

• Introduction

• DSX experimental payloads

• Science question – where is the 20 dB?

• Science question – how efficient are antennas in a plasma?

• Engineering requirement – mapping MEO

• Summary

DSX Mission Objectives

Three science experiments:

1) Wave-particle interactions (WPIx)

• Determine efficiency of injecting VLF into space

plasmas in situ

• Determine global distribution of natural & man-made

ELF-VLF waves

• Characterize and quantify wave-particle interactions

2) Space weather (SWx)

• Map MEO radiation & plasma environment

• Diagnose in-situ environment for wave generation

experiments

3) Space environment effects (SFx)

• Quantify effects of MEO environment on new

technologies

• Determine physical mechanisms responsible for

material breakdown

6000 x 12000 km, 120,

launch ~ Oct 2012

Magnetic phase space

L*

Eq

ua

tori

al p

itc

h-a

ng

le

Wave-Particle Interactions (WPIx)

– VLF transmitter & receivers

– Loss cone imager

– Vector magnetometer

Space Weather (SWx)

– 5 particle & plasma detectors

Space Environmental Effects (SFx)

– NASA Space Environment Testbed

– AFRL effects experiment

8 m

8 m

Y-Axis Booms

• VLF E-field Tx/Rx

Z-Axis Booms

• VLF E-field Rx

AC Magnetometer

– Tri-axial search coils

DC Vector Magnetometer

Loss Cone Imager

- High Sensitivity Telescope

- Fixed Sensor Head VLF Transmitter & Receivers

- Broadband receiver

- Transmitter & tuning unit

DSX Experimental Apparatus

ESPA Ring• Interfaces between EELV

& satellite

DSX satelliteDSX being integrated!

Boom deployment test

• Receiver (Stanford, Lockheed-Martin, NASA/Goddard):

– Three search coil magnetometers (3 B components)

– Two dipole antennas (2 E components)

– Frequency range: 100 – 50 kHz

– Sensitivity 1.0e-16 V2/m2/Hz (E) & 1.0e-11 nT2/Hz (B)

• Transmitter (UMass Lowell, SWRI, Lockheed-Martin):

– 3 – 50 kHz at up to 500 kV (900 kV at end of life)

– 50 – 750 kHz at 1W (local electron density)

• Loss Cone Imager (Boston University, AFRL)

– High Sensitivity Telescope (HST): measures 100 – 500 keV e- with 0.1

cm2-str geometric factor within 6.5 deg of loss cone

– Fixed Sensor Heads (FSH): 130 deg x 10 deg of pitch angle distribution

for 50 – 700 keV electrons every 167 msec

• Vector Magnetometer (UCLA, UMich)

– 0 – 8 Hz three-axis measurement at 0.1 nT accuracy

Vector magnetometer

Loss Cone Imager

HST & FSH

Transmitter control & tuning units

Broadband receiver &

tri-axial search coils

14 May 2007NASA GSFC 14 May 200714 May 2007NASA GSFC

DSX Wave-Particle Interactions Payload

LEESA

LIPS

HIPS

HEPS

0.0001 0.001 0.01 0.1 1 10 100 1000

Energy (MeV)

LEESA

LIPS

HIPS

Protons

Electrons

LEESA

LIPS

HIPS

HEPS

0.0001 0.001 0.01 0.1 1 10 100 1000

Energy (MeV)

LEESA

LIPS

HIPS

Protons

ElectronsCEASE

CEASE

LCI-FSH

DSX Space Weather Payload

CEASE - Compact Environment Anomaly Sensor (Amptek, AFRL)

LEESA - Low Energy Electrostatic Analyzer (AFRL)

LIPS - Low Energy Imaging Particle Spectrometer (PSI)

HIPS - High Energy Imaging Particle Spectrometer (PSI)

HEPS - High Energy Particle Sensor (Amptek, ATC)

Comprehensive SWx sensor suite will map full range of MEO

space particle hazards

HEPS

CEASE

HIPS

LIPS

LEESA

Radiation beltsRing current & auroraPlasmasphere

Energy (MeV)

HEPS

CREDANCE

SET Carrier (NASA-GSFC)

DSX Space Weather Effects Payload

NASA Space Environment Testbed (SET)

• Correlative Environment Monitor (QinetiQ)

– Dosimeter & deep-dielectric charging package

• DIME (Clemson Univ)

– Dosimetry Intercomparison and Miniaturization

• ELDRS (Arizona State)

– Development of space-based test platform for the

characterization of proton effects and Enhanced Low

Dose Rate Sensitivity (ELDRS) in bipolar junction

transistors

• COTS-2 (CNES and NASA)

– Validation of single event effects mitigation via fault

tolerant methodology

AFRL/PRS “COTS” sensors

Radiometers

Photometers

1”

Objective: directly measure changes in

• Optical transmission,

• Thermal absorption

• Thermal emission

due to MEO radiation environment

SFx experiments will quantify MEO environment effects on advanced

spacecraft technologies & determine basic physics of breakdown

NPM VLF

transmitter

Power flux on the ground (LFCOM) Power flux at 1000 km (LFCOM + Helliwell)

Power flux in the magnetosphere

(LFCOM + Helliwell + PowerTrace)

Science QuestionGround-based VLF Injection

Sequence of

“standard”

models used to

estimate VLF

distribution in

space

≠

Science QuestionWhere is the 20 dB?

Abel & Thorne (1998) Starks, et al. (2008)

Ground transmitter VLF needed in the inner magnetosphere… but where is it?

If not ground transmitters – then what?

Could lightning be more effective then previously thought?

• The four models

operate entirely

differently: empirical,

mode theory, finite

differences, full wave

• All predict essentially

the same ionospheric

penetration fields

• However, all of them overestimate the fields by 20 dB or more.

Questions:

• Where is the transmitter power going?

– Non-linear lower-hyrbid wave – density fluctuation scattering?

• What is scattering the particles at L < 2 ?

–Could lightning be more effective then previously thought?

Science QuestionIt’s not the Absorption Model…

Jul Dec

DSX – RBSP

Magnetic Field Line Footprints

Lightning Flash Rates

1 week

(typical)

DSX

Plasma Environment

Magnetic field

Plasma density

Characteristic frequencies

Radius (Re)

B (

Ga

us

s)

n (

#/c

m^

3)

DSX transmitter

DSX Cold Plasma Regime

S=0

mi/me

R

R

X

L

X

R

R

L

X O

R

L

O

L=0

X

Vacuum

limit

Science QuestionWhat is the Radiation Efficiency?

V = V2-V1

I1 I2

+_

++

+

+ +

+

+ ++

__

__

___

_ _

__

_

Iplasma

• Far-field power radiated ~ 1 2 plasma

dI I I

dt

• Antenna fields heat local plasma

• Anisotropic medium dictates complex power flow

1 2

More complex than in vacuum…

DSX Spiral Modeling Approach

Sheath & plasma heating effects included

Vacuum – dipole radiation in vacuo out to 10 km then cold

plasma propagation

Linear cold plasma – voltage and current distribution

specified on antenna immersed in a cold plasma

Self-consistent linear cold plasma – voltage on terminals

specified, current distribution calculated self-

consistently for antenna immersed in a cold plasma

DSX Global Power Distribution – 3 kHz

Critical Unknown:

Importance of scattering and mode-conversion on power and k-spectrum

3 kHz 6000 km

EQUATORIAL PLANE

L=2

L=3

L=4

L=3

L=4

MERIDIONAL PLANE

Satellite at 6000 km altitude, 0° magnetic lat, vacuum antenna limit; 3 kHz

EQUATORIAL PLANE

L=2

L=3

L=4

L=3

L=4

MERIDIONAL PLANE

Magnetospheric reflection destines rays for lower altitudes at 10 kHz as

compared to 3 kHz


DSX Global Power Distribution – 10 kHz

The off-equatorial transmitters lead to very complex field distributions.

L=3

L=4

MERIDIONAL PLANEEQUATORIAL PLANE

L=2

L=3

L=4


DSX Global Power Distribution – Off Equator

Same “field line” Same “drift shell & pitch angle”

DSX – RBSP

Magnetic Conjunctions

DSX – RBSP

Physical Conjunctions

Closest approach ~ 422 km

Same “point”

Outer BeltInner Belt

Slot

HEO

RBSP

ICO

TSX5

DSX

GEO

LEO

Satellite designers need a definitive model of the trapped energetic particle and plasma environment to include:

Quantitative accuracy

Indications of uncertainty

Flux probability of occurrence and worst cases for different exposure periods

Broad energy ranges

Complete spatial coverage

MEO is sorely under sampled!

L ~ Equatorial Radial Distance (RE)

HEO

GPS

GEO

0

50

100

150

200

250

CR

RE

S M

EP

-SE

U A

no

malies

0

CR

RE

S V

TC

W A

no

malies

Slot

5

10

15

1 2 3 4 5 6 7 80

10

20

30

SC

AT

HA

Su

rface E

SD

SEUs

Internal

Charging

Surface

Charging

(Dose behind 82.5 mils Al)

SCATHA

DSX Why Map the MEO Environment?

UNCLASSIFIED23

En

erg

y (

keV

)

TEM1c PC-1 (45.12%)

keV

2 3 4 5 6 7 8

102

103

104

TEM1c PC-1 (45.12%)

2 3 4 5 6 7 8

102

103

104

TEM1c PC-2 (19.15%)

keV

2 3 4 5 6 7 8

102

103

104

TEM1c PC-2 (19.15%)

2 3 4 5 6 7 8

102

103

104

TEM1c PC-3 (9.36%)

keV

2 3 4 5 6 7 8

102

103

104

TEM1c PC-3 (9.36%)

2 3 4 5 6 7 8

102

103

104

TEM1c PC-4 (6.77%)

keV

L

2 3 4 5 6 7 8

102

103

104

z @ eq

=90o

-1 -0.5 0 0.5 1

TEM1c PC-4 (6.77%)

L

2 3 4 5 6 7 8

102

103

104

log10

Flux (#/cm2/sr/s/keV) @ eq

=90o

-4 -2 0 2 4 6Flux maps

New Standard Radiation Belt Model

AP9/AE9

18 months

L s

hell (

Re)

1.0

7.0

Statistical Monte-Carlo Model User application

Satellite data Statistical & physics based analysis Mission orbit

+ =

• New AP-9/AE-9 model being developed by NRO - AFRL - Aerospace – MIT/LL - LANL consortium

• Provides significant improvement in spectral coverage, error estimation and statistical output

• Needed by satellite engineers to control risk, maximize capability and reduce cost

• Version Beta released Apr 2010 and now being evaluated by 20+ independent spacecraft

engineers from industry and government – Version 1.0 due in June 2011

• Version 2.0 (~2015) will utilize measurements from NASA Radiation Belt Storm Probes (RBSP)

and AFRL DSX missions

DSX - RBSPSummary

• DSX is manifest for launch as secondary payload on DMSP F-19

with launch in Oct 2012

• DSX will provide high latitude wave & particle coverage in the slot

region to complement RBSP low latitude coverage

– Missing 20 dB of VLF power is a big inner magnetosphere

question

• Tremendous opportunities for bi-static VLF transmit-receive

measurements

– Validate chorus – hiss conversion model

– Determine VLF antenna transmission efficiency

• Lots of good science to be done

the demonstrations & science experiment...

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