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Science Requirements. The FGM shall measure DC and low frequency perturbations of the magnetic field  see performance requirements The FGM shall measure time wave and structure propagation between probes

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Science requirements
Science Requirements

  • The FGM shall measure DC and low frequency perturbations of the magnetic field

     see performance requirements

  • The FGM shall measure time wave and structure propagation between probes

  • The FGM shall provide information on plasma currents based on instantaneous magnetic field differences on two or more probes, separated by >0.2RE

    ? modelling requirements?


Performance requirements
Performance Requirements

  • The absolute stability of the FGM shall be less than 1nT

  • The relative stability of the FGM shall be less than 0.1nT

    Sensor Characteristics:

    • offset / time: < 0.1nT/h; < 1nT/year; (+ s/c)

    • offset / temperature: < 0.1nT/°C

    • scale value / temperature: 24ppm (0.8nT/°C at 32000nT)

    • orthogonality / temperature: can be neglected


Performance requirements1
Performance Requirements

  • The FGM resolution shall be less than 0.1nT

  • The FGM science range shall exceed 0-1000nT

    • FGM provides always 0.01nT resolution independently of the external field

    • The maximum feedback field (range) is about 32000nT

    • therefore three 24bit values will be sent to the IDPU

    • 16 bit will be selected for transmission

      10pT if B < 320nT

      160pT if B > 2500nT

      1.2nT if B > 20000nT


Performance requirements2
Performance Requirements

  • The FGM noise level at 1Hz shall be less than 0.1nT

    • Sensor noise is less than 10pT/sqrt(Hz) at 1Hz

  • additional “noise” will be generated by the differential nonlinearity of the 12 bit DAC’s (10% of LSB)

    <1000nT - 50pT(maximum), >1000nT - 1.5nT(maximum)

91pT2/Hz : 9pT/Sqrt(Hz)

26pT rms

pT2

pT


Performance requirements3
Performance Requirements

  • The FGM frequency range shall exceed DC-1Hz

    • primary data (FPGA1 -> FPGA2) are 128Hz mean values (128Hz data: 7.5ms measurement, 0.3ms feedback setting)

    • further averaging will be done by FPGA2 and IDPU

    • Problem: to find the right compromise between telemetry rate, aliasing errors, and spin period interferences.

    • Equator-S: aliasing errors are not detected although bandwidth was to high.

    • Cluster: ratio between spin period and data rate of 100 is sufficient.


Performance requirements4
Performance Requirements

  • The FGM calibration shall ensure 1nT absolute accuracy

    • Determination of 3 offsets and 9 elements of a matrix (scale values, non-orthogonality, sensor orientation)

    • spin of satellite provides 8 of 12

      • offsets perpendicular to spin axis (2): < 0.1nT

      • relation between scale values perp. to spin axis (1): < 10-4

      • non-orthogonality (3): < 5’’

      • orientation to spin axis (2): < 5’’

    • scale values are sufficient known from preflight calibr.

    • orientation depends on mech. alignment of sensor (0.1-1°)

    • spin axis offset is the problem (1nT by known physics)


Resource requirements
Resource Requirements

  • The FGM shall not exceed the allocated mass budget (70g)

    • 36g sensor

    • 30g-40g for the housing


Resource requirements1
Resource Requirements

  • The FGM shall not exceed the allocated power budget (800mW)

    • we need

      • +5Vd & +2.5Vd (FPGA & DAC): 10mA

      • +8Va (excitation & amplifiers): 40mA (30mA+10mA)

      • - 8Va (amplifiers): 10mA

      • +5Va (ADC): 15mA

      • - 5Va (ADC): 15mA

    • 600 mW if all voltages will be provided

    • 800 mW if ADC will be provided by +/- 8V

    • 1000 mW if only +/- 8V is available


Resource requirements2
Resource Requirements

  • The FGM shall meet the following thermal requirement

    • survival temperature range (no-op): –50°C to +65°C

    • operating temperature range (op): –20°C to +40°C

    • cold start: -50°C

  •  tested for Rosetta and VEX

  • design and manufacturing of thermal sensor cover is still tbd


  • Facilities integration and tests
    Facilities Integration and Tests

    • Midex Quality Reqiurements

      • e-parts, see following list

      • fabrication of sensor in BS (no cleanroom environment)

      • calibration (no cleanroom environment) in Magnetsrode, Jeserigerhütten ... (outside of civilisation)

      • calibration facilities for final tests in Graz, Berlin, BS, und Berkeley should be identical, stimulation by coil system to test ranging ...

      • Schedule has to be reworked


    E parts overview

    IDPU

    sense

    excitation

    feedback

    DAC

    ADC

    Sensor

    FPGA

    e-parts: overview

    bold - qualified

    red - preferred

    DAC:

    6 x 8043

    6 x 8143

    FPGA:

    2 x 54SX32

    1 x 54SX72

    Amplifier:

    6 x LT1013

    3 x LT1013 &

    3 x AD648

    ADC:

    3 x AD6764

    3 x AD7872

    Instr. Ampl.:

    3 x AD524

    3 x AD625

    Prec. Resistors.:

    Megatron MMQ / MMP

    Voltage Reference:

    1 x LT1013

    Driver:

    1 x HS9-4424

    1 x MIC4425

    Line Regulators:

    LM117 & LM137


    Contamination requirement
    Contamination Requirement

    • all instruments shall comply with the MC standard

      • UCLA responsibility

      • if necessary we can provide

        • ESTEC software

        • turntable to determine magnetic moments

        • gradiometer mounted on a guide bar to estimate s/c field


    Operation
    operation

    • operation during ...

      • all science phases in the same mode

      • all technically interesting phase (orbit change, eclipse)

    • FGM should be switched on before boom deployment


    Idpu requirements
    IDPU requirements

    • FGM software

      • selection of 16bit, orbit controlled or auto-controlled

      • despin onboard?

      • relation to other experiments

      • test data necessary?

      • responsibility?

    • FGM hardware

      • clock / timing


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