Flight results from the Merlin space weather monitor on Giove-A

Flight results from the Merlin space weather monitor on Giove-A

3rd European Space Weather Week 13-17 November 2006, Brussels

K A Ryden, P A Morris, D J Rodgers, C S Dyer - QinetiQC I Underwood, B. Taylor, S Jason - SSTL/ University of SurreyH D Evans, E J Daly, G Mandorlo, G Gatti - ESA/ESTEC

Giove-A

• Test-bed for European Galileo GNSS

– obtain frequency filing protection

– characterise the MEO environment

– validate certain critical payloads

– provide representative signal-in-space transmission

• Built and operated by SSTL

• Successfully launched in December 2005

• Orbit 23,260 km and 56 degrees inclination, 27 month lifetime

– electron dominated: charging and total dose hazards

– exposed to solar particle eventsSSTL image

Galileo orbit

• Severe trapped electron environment– Charging effects

– Total ionising dose

• Galactic cosmic rays

• Solar protons and ions GALILEO altitudeGALILEO altitude

Total ionising dose

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

0 2 4 6 8 10 12 14 16 18 20Thickness of Al sphere [mm]

GPS Total

GEO Total

GTO Total

Internal charging

• ESD transients can cause anomalies and outages

• Cables, connectors, pcbs etc

High energy electrons from space environment

Dielectric

Shielding

Merlin space weather hazard monitor

• Electrons and charging

• Total ionising dose

• Protons

• Ions (LET)

• 1kg, 2.5W (standard)

Developed from the earlier CREDO and SURF science detectors

QinetiQ space radiation monitors

CREAM Cosmic Ray Effects and Activation Monitor (1986 onward)

• Charge deposition events in Si

• Flights: Shuttle(10 flights) /BA Concorde/Qantas/

CREDO Cosmic Ray Effects and Dosimetry Experiment (1991 onward)

• Ion LET spectra and proton flux

• Flights: UoSAT, STRV1a, Skynet, APEX, MIR, MPTB

SURF (2000 onward)

• Surface charging and internal charging (electron flux)

• Flights: STRV1d

Merlin (2005 onward)

• Charging/LET spectra/proton flux/TiD

• Flights: Giove-A, LWS/SET

Merlin space weather hazard monitor

Electrons & electrostatic charging (3 shielding depths)

Ions (linear energy transfer)

Protons (>40 MeV flux)

Total dose RADFET (x2)

Integral rad-hard computer, data storage, power conditioning and communications

Ion telescope Protontelescope

Total dosemonitor

Internalcharging(electron)monitor

Energydiscriminator

Analogueprocessingand ADC

Microcomputer and memory

Powerconditioningand filtering

RS422 businterface

RS422 bus Power bus

Lower board

Upper board

Merlin block diagram

Sensor suite (CREDO + SURF + Radfet)

Data handling

Merlin-Giove-A

Electrons & charging: SURF experiment

• Novel approach– internal charging current vs depth

measurement

– each plate has unique energy response curve so spectrum can be obtained

• Virtually immune to proton contamination

• Built and flown on STRV1d

• 300g, 0.3W

Space radiationparticles

Satellitetelemetry system

Lid 0.6mm Al

0.5mm Al plate1.0mm Al plate

Satellite exteriorwall

Satellite groundreference

fA fA

.

SURF experiment: internal charging mode

0.00E+00

5.00E-10

1.00E-09

1.50E-09

2.00E-09

2.50E-09

3.00E-09

0 1 2 3 4 5 6

Electron energy (MeV)

Top plate

Bottom plate

SURF results

• GTO orbit

• 500 x 36,000 km

Merlin-Giove-A

• Located externally (under thermal blanket)

• Extra box shielding incorporated (5mm thick walls) due to severity of orbit

• SURF and Radfet set-up for Giove-A:

SURF plates

Housing (lid)

RADFETS

0.4 mm Al

2 mm Al

5 mm Al

0.5 mm Al

1 mm Al

Thermal blanket - 0.1 mm Al eq.

Merlin pre-flight calibration

SURF plates

Housing (lid)

RADFETS

0.4 mm Al

2 mm Al

5 mm Al

0.5 mm Al

1 mm Al

Thermal blanket <0.2 mm Al eq.

REEF Sr-90 source

Realistic Electron Environment Facility

• 90Sr source: 3.7 G Bq• Vacuum chamber• -10 to +40°C temperature

control of thermal plate• Electron current

controlled by variation of source-to -sample distance

• ESD detection system• Surface potential

measurements (‘TREK’ probes)

Electron spectrum comparisons• REEF

capability brackets the average (AE8) and worst-case (FLUMIC) electron environments predicted for GEO

0.01

0.1

1

10

0.1000 1.0000 10.0000Energy (MeV)

Cur

rent

(pA

/cm

2 )

REEF (30mm) REEF (187.5mm)

Average GEO (AE-8min) NASA worst case GEOWorst case GEO (FLUMIC)

Merlin-Giove-A: pre-flight calibration (REEF)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 50 100 150 200

time / s

char

ging

cur

rent

pA

/cm

2

0,5 mm shield, 0.5 mm collector

1.0 mm shield, 0.5 mm collector

1.5 mm shield, 1.0 mm collector

Source position: 0

Source position: 135,000

Merlin pre-flight calibration in REEF

• Two particle telescopes (CREDO)– ion LET spectrum

– protons (400 keV energy deposition threshold)

Pul

se h

eigh

t dis

crim

inat

orCOINCIDENCE GATE

SIGNAL

Si diode, area 3cm2, 300um thick

NON-COINCIDENCE COUNTERS

COINCIDENCE COUNTERS

Merlin-Giove-A

Radiation monitors installed on Giove-A

Picture: SSTL

Launch 28th December 2005

MERLIN-GIOVE A: CHARGING CURRENTS DUE TO TRAPPED ELECTRONS

0.00

0.05

0.10

0.15

0.20

29/12/2005 15:36:00 29/12/2005 20:24:00 30/12/2005 01:12:00 30/12/2005 06:00:00 30/12/2005 10:48:00 30/12/2005 15:36:00

Date

Cu

rren

t (p

A/c

m2)

0

5

10

15

20

25

30

L (

Re)

:

B (

kGau

ss)

Shield 0.5mm, collector 0.5mmShield 1.0mm, collector 0.5mmShield 1.5mm, collector 1.0mmB (model)L (model)

1st day of data: electrons/charging

GALILEO altitudeGALILEO altitude

Jan & Feb 2006: electrons/charging

Jan & Feb 2006: electrons & dose

21 Feb 2006 electron eventMERLIN-GIOVE A: CHARGING CURRENTS DUE TO TRAPPED ELECTRONS

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

21/02/200600:00

21/02/200602:24

21/02/200604:48

21/02/200607:12

21/02/200609:36

21/02/200612:00

21/02/200614:24

21/02/200616:48

21/02/200619:12

21/02/200621:36

22/02/200600:00

Date

Cu

rren

t (p

A/c

m2)

0

5

10

15

20

25

30

L (

Re)

:

B (

kGau

ss)


6 days laterMERLIN-GIOVE A: CHARGING CURRENTS DUE TO TRAPPED ELECTRONS

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

27/02/200600:00

27/02/200602:24

27/02/200604:48

27/02/200607:12

27/02/200609:36

27/02/200612:00

27/02/200614:24

27/02/200616:48

27/02/200619:12

27/02/200621:36

28/02/200600:00

Date

Cu

rren

t (p

A/c

m2)

0

5

10

15

20

25

30

L (

Re)

:

B (

kGau

ss)


Jan-May 2006: electrons & dose

April 06 electron event

April 06 electron event

Single belt transit – 17th April 2006

Merlin-Giove-A: Single transit though belt 17 April 2006

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

17/04/2006 09:21 17/04/2006 10:33 17/04/2006 11:45 17/04/2006 12:57 17/04/2006 14:09

day/month/year/time

de

po

sit

ed

cu

rre

nt

/ p

A c

m-2

3.40

3.45

3.50

3.55

3.60

3.65

3.70

3.75

3.80

pro

vis

ion

al

do

se

/ k

rad

(SiO

2)

charging current (0.5mmshield, 0.5 mm collector)

charging current (1.0mmshield, 0.5mm collector)

charging current (1.5mmshield, 1.0mm collector)

dose (3mm Al eq. in +zdirection)

Jan-Aug 2006: electrons and dose

Jan-Aug 2006: electrons and dose

AE8/sectored shielding model of the expected dose.

Sept & Oct 2006: electrons and dose

Giove-A/Merlin charging currents and dose

0

0.05

0.1

0.15

0.2

0.25

28/12/2005 27/01/2006 26/02/2006 28/03/2006 27/04/2006 27/05/2006 26/06/2006 26/07/2006 25/08/2006 24/09/2006 24/10/2006

Date

Cu

rre

nt

pA

/cm

2

0

2

4

6

8

10

12

Do

se

kR

ad

s(S

iO2

)

Shield 0.5mm collector 0.5mmShield 1.0mm collector 0.5mmShield 1.5mm collector 1.0mmRadFET shield 6mmRadFET shield 3mm

Jan-Oct 2006: electrons and dose(D

aily

ave

rag

e)

Jan-Aug 2006: electrons and FLUMIC seasonal modulation function

Giove-A/Merlin: 1-Day Mean Charging Current

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

30/12/2005 18/02/2006 09/04/2006 29/05/2006 18/07/2006 06/09/2006 26/10/2006

Date

Ch

arg

ing

cu

rre

nt

pA

/cm

2

FLUMIC

shield 0.5mm, collector 0.5mm

Jan-Oct 2006: top SURF plate compared to DICTAT worst case


0.00

0.05

0.10

0.15

0.20

0.25

30/12/2005 18/02/2006 09/04/2006 29/05/2006 18/07/2006 06/09/2006 26/10/2006

Date

Ch

arg

ing

cu

rre

nt

pA

/cm

2

FLUMIC


Jan-Oct 2006: middle SURF plate compared to DICTAT worst case


0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

30/12/2005 18/02/2006 09/04/2006 29/05/2006 18/07/2006 06/09/2006 26/10/2006

Date

Ch

arg

ing

cu

rre

nt

pA

/cm

2

FLUMIC


Jan-Oct 2006: bottom SURF plate compared to DICTAT worst case

Jan-Aug 2006: electron spectrum ‘hardness’

6th July 2006 – minor SPEGiove-A/Merlin

6th July 2006 event

0.001

0.01

0.1

1

10

100

05 July 12:00 06 July 00:00 06 July 12:00 07 July 00:00 07 July 12:00 08 July 00:00 08 July 12:00 09 July 00:00

Date

Flu

x (

cm

-2.s

-1)

0.0001

0.001

0.01

0.1

1

10

100

Cu

rren

t (p

A/c

m2 )

Coincident ProtonsIon channel 1Charging current

Merlin Giove-A Integral LET Spectra 1st Aug - 31st Oct 2006

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

1.E+02

10 100 1000 10000 100000

LET (MeV/(g.cm -2))

Inte

gra

l F

lux (

m -2

.s -1

.sr

-1)

IonsCREME96

Background LET spectrum

Conclusions• Good data from all Merlin sensors

– Electrons/charging rates measured at three shielding depths

– Total dose at two shielding depths

– > 40 MeV protons (500 keV deposition threshold to be sure of protons)

– LET spectrum (background)

• Numerous electron enhancement events have been observed via the charging (electron deposition) and total dose effects

• Clear 27 day interval in electron enhancements (persistent coronal holes)

• April ‘event’ was the most severe so far – ‘worst case’ events are of engineering significance and their magnitude needs to be captured

– April event still produced less than DICTAT ‘worst case’ predicted charging currents for the plates

…..conclusions

• Ionising dose is delivered in surges during the electron events

• From Jan to August 2006, approximately half of the dose was delivered by just one electron event

• Dose at 6mm shield depth (Merlin +z direction) observed is greater than the predicted value (using AE8/sectored shielding models) at this stage: however may not be typical of whole solar cycle

• Post-script

– 2nd Merlin for NASA ‘Living with a Star’ now built & qualified

Documents

Flight results from the Merlin space weather monitor on Giove-A