1. 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?

2. 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

3. Performance Requirements
The FGM resolution shall be less than 0.1nT
The FGM science range shall exceed nT
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 < nT
160pT if B > nT
1.2nT if B > 20000nT

4. Performance Requirements
The FGM noise level at 1Hz shall be less than 0.1nT
Sensor noise is less than 10pT/sqrt(Hz) at 1Hz
26pT rms
91pT2/Hz : 9pT/Sqrt(Hz)
pT2 pT
additional “noise” will be generated by the differential nonlinearity of the 12 bit DAC’s (10% of LSB)
<1000nT pT(maximum), >1000nT nT(maximum)

5. 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.

6. 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)

7. Resource Requirements
The FGM shall not exceed the allocated mass budget (70g)
36g sensor
30g-40g for the housing

8. 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

9. 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

10. 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

11. e-parts: overview DAC: FPGA: Amplifier: ADC: Instr. Ampl.:
bold - qualified
red preferred
DAC
IDPU
Sensor
ADC
FPGA
feedback
sense
excitation
FPGA:
2 x 54SX32
1 x 54SX72
DAC:
6 x 8043
6 x 8143
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

12. 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

13. FGM should be switched on before boom deployment
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

14. IDPU requirements FGM software FGM hardware
selection of 16bit, orbit controlled or auto-controlled
despin onboard?
relation to other experiments
test data necessary?
responsibility?
FGM hardware
clock / timing