Flight results from the Merlin space weather monitor - The Merlin

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					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 - QinetiQ
C I Underwood, B. Taylor, S Jason - SSTL/ University of Surrey
H 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              SSTL image

      – electron dominated: charging and
        total dose hazards
      – exposed to solar particle events
Galileo orbit
• Severe trapped
  electron environment
   – Charging effects
   – Total ionising dose

• Galactic cosmic rays
• Solar protons and
  ions                     GALILEO altitude
Total ionising dose
Internal charging
         High energy electrons from space environment


                                                        Shielding



        Dielectric




• ESD transients can cause anomalies and outages
• Cables, connectors, pcbs etc
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)                                                   SURF (2000 onward)
• Ion LET spectra and proton flux                         • Surface charging and internal charging
                                                          (electron flux)
• Flights: UoSAT, STRV1a, Skynet, APEX,
MIR, MPTB                                                 • 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)

                               Total dose
                               RADFET (x2)

                               Protons (>40 MeV
                               flux)

                               Ions (linear energy
                               transfer)



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

       Ion telescope      Proton          Total dose            Internal
                        telescope          monitor             charging
                                                              (electron)
                                                                monitor             Sensor suite
          Energy                                  Analogue
                                                                                    (CREDO + SURF +
       discriminator                             processing                         Radfet)
                                                  and ADC
                                                                      Upper board



                                                                      Lower board

                       Microcomputer and memory

                                                                                    Data handling
                                                                Power
                                                              conditioning
                             RS422 bus
                                                              and filtering
                              interface




                             RS422 bus                        Power bus
Merlin-Giove-A
 Electrons & charging: SURF experiment
• Novel approach
   – internal charging current vs depth          Space radiation    Lid 0.6mm Al
     measurement                                   particles

   – each plate has unique energy response                          0.5mm Al plate
                                                                    1.0mm Al plate
     curve so spectrum can be obtained
• Virtually immune to proton contamination                          Satellite exterior
                                                  fA       fA       wall
• Built and flown on STRV1d
• 300g, 0.3W
                                                     Satellite      Satellite ground
                                                 telemetry system   reference



                                             .
SURF experiment: internal charging mode
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:

                                                                        2 mm Al
     Thermal blanket - 0.1 mm Al eq.
                                            0.4 mm Al   Housing (lid)


                                                         5 mm Al

                              SURF plates
    0.5 mm Al
       1 mm Al                                                RADFETS
Merlin pre-flight calibration

        REEF Sr-90
            source




                                                                          2 mm Al
        Thermal blanket <0.2 mm Al eq.
                                              0.4 mm Al   Housing (lid)


                                                           5 mm Al

                                SURF plates
       0.5 mm Al
          1 mm Al                                               RADFETS
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
                         REEF (30mm)                    REEF (187.5mm)
                         Average GEO (AE-8min)          NASA worst case GEO
                                                                                   capability
                         Worst case GEO (FLUMIC)                                   brackets the
                   10                                                              average (AE8)
                                                                                   and worst-case
Current (pA/cm2)




                                                                                   (FLUMIC)
                    1
                                                                                   electron
                                                                                   environments
                   0.1                                                             predicted for
                                                                                   GEO
           0.01
                    0.1000   Energy (MeV)      1.0000                  10.0000
Merlin pre-flight calibration in REEF
                                                  Merlin-Giove-A: pre-flight calibration (REEF)

                             0.6
                                       0,5 mm shield, 0.5 mm collector          Source position: 135,000

                             0.5       1.0 mm shield, 0.5 mm collector

                                       1.5 mm shield, 1.0 mm collector
   charging current pA/cm2




                             0.4


                             0.3
                                           Source position: 0
                             0.2


                             0.1


                              0
                                   0             50                      100                    150        200
                                                                     time / s
Merlin-Giove-A
• Two particle telescopes (CREDO)
   – ion LET spectrum
   – protons (400 keV energy deposition threshold)




                                           Pulse height discriminator
                                                                                 COINCIDENCE COUNTERS
         Si diode, area 3cm2, 300um                                     NON-COINCIDENCE COUNTERS
                     thick




                                          COINCIDENCE GATE
                                               SIGNAL
Radiation monitors installed on Giove-A




                               Picture: SSTL
Launch 28th December 2005
            1st day of data: electrons/charging
                                            MERLIN-GIOVE A: CHARGING CURRENTS DUE TO TRAPPED ELECTRONS

                                                                                                                                                 30
                                                                                                              Shield 0.5mm, collector 0.5mm
                                                                                                              Shield 1.0mm, collector 0.5mm
                      0.20
                                                                                                              Shield 1.5mm, collector 1.0mm
                                                                                                              B (model)                          25
                                                                                                              L (model)



                      0.15
                                                                                                                                                 20




                                                                                                                                                       L (Re) : B (kGauss)
Current (pA/cm2)




                                                                                                                                                 15
                      0.10



                                                                                                                                                 10


                      0.05

                                                                                                                                                 5




                       0.00                                                                                                                       0
                   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
                                                                                                                                              GALILEO altitude
                                                                                     Date
Jan & Feb 2006: electrons/charging
Jan & Feb 2006: electrons & dose
                          21 Feb 2006 electron event
                                          MERLIN-GIOVE A: CHARGING CURRENTS DUE TO TRAPPED ELECTRONS

                   0.40                                                                                                                30
                                Shield 0.5mm, collector 0.5mm
                                Shield 1.0mm, collector 0.5mm
                   0.35         Shield 1.5mm, collector 1.0mm
                                B (model)                                                                                              25
                                L (model)
                   0.30

                                                                                                                                       20




                                                                                                                                            L (Re) : B (kGauss)
                   0.25
Current (pA/cm2)




                   0.20                                                                                                                15



                   0.15
                                                                                                                                       10

                   0.10

                                                                                                                                       5
                   0.05



                   0.00                                                                                                                 0
                   21/02/2006 21/02/2006 21/02/2006 21/02/2006 21/02/2006 21/02/2006 21/02/2006 21/02/2006 21/02/2006 21/02/2006 22/02/2006
                      00:00      02:24      04:48      07:12      09:36      12:00      14:24      16:48      19:12      21:36      00:00
                                                                             Date
                     6 days later
                                         MERLIN-GIOVE A: CHARGING CURRENTS DUE TO TRAPPED ELECTRONS

                   0.40                                                                                                                 30
                                                                                                        Shield 0.5mm, collector 0.5mm
                                                                                                        Shield 1.0mm, collector 0.5mm
                   0.35                                                                                 Shield 1.5mm, collector 1.0mm
                                                                                                        B (model)                       25
                                                                                                        L (model)
                   0.30

                                                                                                                                        20




                                                                                                                                             L (Re) : B (kGauss)
                   0.25
Current (pA/cm2)




                   0.20                                                                                                                 15



                   0.15
                                                                                                                                        10

                   0.10

                                                                                                                                        5
                   0.05



                   0.00                                                                                                                 0
                   27/02/2006 27/02/2006 27/02/2006 27/02/2006 27/02/2006 27/02/2006 27/02/2006 27/02/2006 27/02/2006 27/02/2006 28/02/2006
                      00:00      02:24      04:48      07:12      09:36      12:00      14:24      16:48      19:12      21:36      00:00
                                                                             Date
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
                                 0.80                                                                                                 3.80
                                             charging current (0.5mm
                                             shield, 0.5 mm collector)
                                 0.70                                                                                                 3.75
                                             charging current (1.0mm
                                             shield, 0.5mm collector)
                                 0.60        charging current (1.5mm                                                                  3.70




                                                                                                                                             provisional dose / krad(SiO2)
 deposited current / pA cm-2




                                             shield, 1.0mm collector)

                                 0.50        dose (3mm Al eq. in +z                                                                   3.65
                                             direction)

                                 0.40                                                                                                 3.60


                                 0.30                                                                                                 3.55


                                 0.20                                                                                                 3.50


                                 0.10                                                                                                 3.45


                                 0.00                                                                                                 3.40
                               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
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
Jan-Oct 2006: electrons and dose
                                                                             Giove-A/Merlin charging currents and dose
                                 0.25                                                                                                                                           12
                                                 Shield 0.5mm collector 0.5mm
                                                 Shield 1.0mm collector 0.5mm
                                                 Shield 1.5mm collector 1.0mm
Current pA/cm2 (Daily average)




                                                 RadFET shield 6mm
                                                                                                                                                                                10
                                                 RadFET shield 3mm
                                  0.2



                                                                                                                                                                                8




                                                                                                                                                                                     Dose kRads(SiO2)
                                 0.15


                                                                                                                                                                                6


                                  0.1

                                                                                                                                                                                4



                                 0.05
                                                                                                                                                                                2




                                   0                                                                                                                                            0
                                 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
Jan-Aug 2006: electrons and FLUMIC
seasonal modulation function
         Jan-Oct 2006: top SURF plate compared to
         DICTAT worst case
                                                    Giove-A/Merlin: 1-Day Mean Charging Current

                          0.70
                                                                      FLUMIC
                                                                      shield 0.5mm, collector 0.5mm

                          0.60



                          0.50
Charging current pA/cm2




                          0.40



                          0.30



                          0.20



                          0.10



                          0.00
                          30/12/2005   18/02/2006   09/04/2006        29/05/2006            18/07/2006   06/09/2006   26/10/2006
                                                                          Date
                    Jan-Oct 2006: middle SURF plate compared
                    to DICTAT worst case
                                                    Giove-A/Merlin: 1-Day Mean Charging Current

                          0.25
                                                                       FLUMIC
                                                                       shield 1.0mm, collector 0.5mm


                          0.20
Charging current pA/cm2




                          0.15




                          0.10




                          0.05




                          0.00
                          30/12/2005   18/02/2006   09/04/2006       29/05/2006            18/07/2006   06/09/2006   26/10/2006
                                                                         Date
Jan-Oct 2006: bottom SURF plate compared
to DICTAT worst case
                                                     Giove-A/Merlin: 1-Day Mean Charging Current

                          0.16

                                                                          FLUMIC
                          0.14                                            shield 1.5mm, collector 1.0mm



                          0.12
Charging current pA/cm2




                          0.10



                          0.08



                          0.06



                          0.04



                          0.02



                          0.00
                          30/12/2005   18/02/2006   09/04/2006       29/05/2006           18/07/2006      06/09/2006   26/10/2006
                                                                         Date
Jan-Aug 2006: electron spectrum ‘hardness’
                     6th July 2006 – minor SPE
                                                                             Giove-A/Merlin
                                                                           6th July 2006 event
                     100                                                                                                                     100
                                     Coincident Protons
                                     Ion channel 1
                                     Charging current
                                                                                                                                             10
                       10


                                                                                                                                             1




                                                                                                                                                       Current (pA/cm2)
Flux (cm -2.s -1)




                        1

                                                                                                                                             0.1

                      0.1
                                                                                                                                             0.01


                     0.01
                                                                                                                                             0.001



                    0.001                                                                                                                     0.0001
                     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
                              Background LET spectrum
                                                      Merlin Giove-A Integral LET Spectra
                                                            1st Aug - 31st Oct 2006
                                  1.E+02
                                                                                                    Ions
                                                                                                    CREME96
                                  1.E+01
Integral Flux (m -2.s -1.sr -1)




                                  1.E+00



                                  1.E-01



                                  1.E-02



                                  1.E-03



                                  1.E-04
                                           10   100                      1000               10000             100000
                                                                                  -2
                                                                  LET (MeV/(g.cm ))
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

				
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