TRIO-CINEMA 1 UCB, 2/08/2010 MAGIC Patrick Brown Imperial College London

TRIO-CINEMA 2 UCB, 2/08/2010 MAGIC – Magnetometer from Imperial College Purpose Dual tri-axial magnetoresistive sensor measures magnetic field vector local to spacecraft in frequency range 0-10Hz Role of magnetometer Contribute to spacecraft attitude determination Measurement of local field direction for pitch angle determination Detection and characterisation of local waves and structures Parts Outboard sensor head Electronics board Inboard sensor (on electronics board) Harness (UCB supplied)

TRIO-CINEMA 3 UCB, 2/08/2010 Magnetoresistive magnetometer Implementation – analogue closed loop Bipolar driving to maintain optimum detectivity Requires current pulse of 4A for 2ms Dynamic Offset compensation employed 3axis Fluxgate Single axis MR

TRIO-CINEMA 4 UCB, 2/08/2010 Three Axis MAGIC Implementation Note: IB sensor & electronics not identical to OB

TRIO-CINEMA 5 UCB, 2/08/2010 MAGIC Requirements MAGIC Requirements (requires updating). See MAGIC ICD (Latest version ) SCI-18MAG DirectionReconstruct field direction to 1 degree OBJ-03 SCI-19MAG Field Accuracy <500nT (preferably much better) OBJ-03 SCI-20MAG CadenceMeasure field variations at better than 1s OBJ-03 SCI-21MAG Resolutionresolve phenomena at amplitudes of 100nT on timescales of few seconds [~1nT desirable] OBJ-03 Level 2 MAGIC MAG-01MAG Measurements 3-axis inboard and 3-axis outboard MAG sensors (normally not at the same time). Outboard sensor deployed to ~1m from the body of the spacecraft. MAG-02MAG Range+/-65536nT MAG-03MAG Resolution25nT attitude mode, 10nT Science Mode A, 2nT Science mode B [with noise in the same range at 1Hz] SCI-21 MAG-04MAG AccuarcyGains calibrated to 0.5% (including temperature variability)SCI-19 MAG-05MAG Sample Rate 4 samples/sec attitude mode, 8 samples/sec science mode (TBR)SCI-20 MAG-06MAG Data Interface SPI Interface and clock per MAGIC ICD MAG-07MAG Power100mW attitude mode, 500mW science mode A, 750mW science mode B MAG-08MAG Voltages3.6V, 5V, 12V, 20V

TRIO-CINEMA 6 UCB, 2/08/2010 Sensor Head (Outboard Sensor) CINEMA Boom very light MAG Harness requires at least 17 lines Boom can only support very thin gauge wire Line loss on 4A pulse too large Solution MAGIC Sensor Head Install sensor drive electronics with sensor Inboard sensor in mounted directly on PCB MAGIC Test Harness

TRIO-CINEMA 7 UCB, 2/08/ Hybrid three axis sensor Since KHU meeting – have discovered some head parts are magnetic (lead frames, capacitors) Solution: Implement sensor drive circuit at die level Funded by ESA to manufacture prototype demonstrator for separate project Design assessment currently ongoing – awaiting quote for EM manufacture Three axis head (home made)Ceramic Hybrid

TRIO-CINEMA 8 UCB, 2/08/2010 MAGIC Power Default Science Mode

TRIO-CINEMA 9 UCB, 2/08/2010 Performance testing – Fluxgate vs AMR 8nT ptp 2Hz Square Wave 2nTptp 2Hz Sine Wave

TRIO-CINEMA 10 UCB, 2/08/2010 Test results on most recent design Note MR bridge is this instance only 5V – a considerable power saving over a 12V bias. Saves ~130mW per axis. Compare to 16V flipping power ~ 120mW for all three axis

TRIO-CINEMA 11 UCB, 2/08/2010 Sensor head mechanical interface design led by UCB Harness supplied by UCB –Magnet wire with Aracon outer braid –Aracon slightly magnetic –Last 10cm near head will be silver over copper Original Provisional Integration Plan –UCB Manufacture harness with flying wires –Imperial integrate harness to sensor head/add non magnetic braid piece –Imperial install MAGIC connecter for test and calibration –Imperial remove bus connector prior to delivery –UCB or Imperial add bus connector following head installation on boom –IS THIS STILL VALID – CAN WE DELIVER UNREMOVABLE CONNECTOR ? Harness Connector at MAGIC PCB – MDM25Way Sensor head mass: <20g (if potted) Prototype Sensor Head: Dimensions 2x2x2cm Inboard sensor in mounted directly on MAGIC card MAGIC PCB Single PC104 card, Mass ~ 150g, clearance 1cm and 0.5cm alternate side (TBC) Strain Relief No Connector MAGIC Mechanical

TRIO-CINEMA 12 UCB, 2/08/2010 MAGIC Harness Connections Sensor Harness connections Connections to bus

TRIO-CINEMA 13 UCB, 2/08/2010 MAGIC Data & Command Interface Interface to bus via ADS1216 –8 channel, 24 bit Delta-Sigma architecture with 8 I/O registers –Has the required channel number, range and H/W control potential –Control interface via SPI –PGA, and on board Sinc filters –Low power consumption ~ a few mW Issues –MAGIC requires the bus to sample the MAGIC data at some TBC rate i.e. switching the MUX at the required cadence –Baseline that MAGIC filtering is performed on board ADC –No CS needed on dsPIC33 if ADS1216 only SPI device –To minimise processing load on bus controller recommend dedicated bus connections for NDREDY and ADC RESET

TRIO-CINEMA 14 UCB, 2/08/2010 MAGIC CMDH Bus Requirements Channel switching of ADC add acquisition of data –7 channels in total OB (Bx, By, Bz) IB (Bx, By, Bz) OB Temp –Not all channels accessed in all modes (default mode is OB and Temp only) –Potential switching of sinc filter, read of ADC register status MAGIC commanding via SPI to ADC –Commanding only defined at functional level –ADC Configure –Switch channel (OB sensor (3), IB Sensor (3) or Temperature) –Switch between Attitude, Science and Gradiometer Modes Data Rates –Attitude Mode 1 vector per second (65 bits per second) –Science Modes 10 vectors per second (578 bits per second) Timing interface – Vectors assumed to be stamped by bus

TRIO-CINEMA 15 UCB, 2/08/2010 Development Plan (1) Development Single axis analogue design exits since 2008 Three axis analogue design ready since Dec 2009 Waiting for ADC test before migration to PCB ADS channel ADC board currently under development ADC Board 1 – developing SPI code connection to analogue MAG ADC Board 2 – to interface to CubeSat board to develop flight pseudo code Expect MAG ADC interface test to take place later this week Proposed Schedule Milestones MAGIC EM PCB Layout from 12 th Feb EM Test & Evaluation starts 26 th March FM Manufacture starts 26 th April FM Test & Cal starts 18 th June Delivery to UCB 5 th August Schedule include milestone for ADC code, STM and ETU delivery

TRIO-CINEMA 16 UCB, 2/08/2010 Development Plan (2) STM Sensor Idea is to deliver a potted sensor head for early stage deployment firing to test robustness of harness termination in potted sensor head Senor head would be dummy i.e. potted set of 17 resistors Would require delivery of sensor harness from UCB. Sensor chassis would be manufactured by IC Proposed delivery date 1 st April EM model Single axis MR with ADC for interface testing prior to FM deliver Would require ADS1216 SPI MAG pseudo-code Proposed delivery date 30 th April

TRIO-CINEMA 17 UCB, 2/08/2010 MAGIC Internal Schedule

TRIO-CINEMA 18 UCB, 2/08/2010 Current Issues ADC –ADS1216 development work ongoing –SPI comms sampling at 100Hz on three MUXed channels now working –Controlled by PC with LabView –Next step is to connect to MAG three axis board –Still a difficult interface. Only V range so need to add attenuator to MAG board –Looking into alternate ADC as a nuclear option (AD1217, ADS1256) ADS1217 – identical interface but bigger range (0-5V) ADS1256 – faster sampling and lower noise but at expense of power ~38mW –Will connect ADS1216 to MAGIC board this week in any case and assess. Sensor Head –MOSFET Lead frames and capacitor are magnetic –Solution: Hybrid sensor built with component die Connectors –Is it OK to deliver MAGIC with sensor harness with un-removeable connector? Calibration –MAGIC Three Axis sensor not yet calibrated due to broken facility –Detailed performance testing waiting for operational ADC interface