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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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