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

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

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 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 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 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

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

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

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