FIELDS MEP PSR - MAGi, MAGo 002C_SPF_MEP_IPSR_MAG_Results FIELDS FM MAGs

FM-1 & FM-2 MAG Status at PSR All environmental and acceptance tests have been completed. A comprehensive suite of calibration tests have been performed. There are no open items, open deviations, open PR/PFRs, or open waivers. All MAG documents and drawings have been released in the GSFC Configuration Management system ( https://ehpdmis.gsfc.nasa.gov ). The End Item Data Packages (EIDP) are complete. A MAG Specification/User’s Manual has been delivered to SSL (LWS-MAG-SPEC-0001) The MAG Calibration Report (LWS-MAG-RPT-0011, Rev. 0) is complete and delivered to SSL GSE for MAGs (e.g., shield can, coil inserts, Stim Rack, dummy loads, etc.) has been delivered to SSL. Shipping containers delivered with MAGs in June 2016. Magnetic screening station delivered to the spacecraft. MAG Pre-Ship Review held at NASA GSFC on April 25, 2016 prior to delivery to SSL for FIELDS integration. (LWS-MAG-RVW-0008)

FM-1 & FM-2 MAG Test and Calibration Status Functional Test Activities completed (at GSFC and SSL): Safe-to-Mate Test Aliveness Test (includes command and telemetry response verification) Voltage, Temperature, and Frequency Margin Testing (VTFMT) 12 thermal cycles on sensor and electronics, -50°C to +75°C Greater than 200 hours trouble-free operation time prior to delivery to SSL Environmental Qualifications completed (at GSFC and SSL) EMI/EMC (with MEP) Vibration (sensor at GSFC / electronics with MEP) Thermal balance (multiple tests with EM sensor) Thermal vacuum (electronics in MEP) at SSL Calibration Activities completed (at GSFC): Scale factors measured in all four ranges Offset determination Scale factor temperature compensation (via EM qualification unit) Sensor orthogonality via Ørsted (“Thin Shell”) method Sensor orthogonality via MAGSAT (optical/magnetic) method System noise Linearity measurement Final Documentation Package completed: End Item Data Packages (EIDP) for the FM-1 and FM-2 MAGs are complete

Main Performance Tests Completed for each MAG (Tests that were completed for each MAG prior to integration with MEP) Test Function Comment Voltage Variation Circuit operation, voltage regulator stability +/-11V to +/-13V (sensor electronics) +22V to +35V (heater electronics) Temperature Variation Verify stability over temperature variation Functional testing at -40°C, +22°C, and +80°C Command/Telemetry Regression Script Exercises all commandable registers and monitors all telemetry bits; MEP IF Automated checking via limit monitoring Frequency Response Verifies tuning stability and AC performance On bench, vary MAG_CK +/- 400 Hz via tri-axial solenoid in shield can Drive Saturation Test Verifies Drive recovery from sensor overload Drive tuning verification Ranging algorithm Verifies manual and autonomous ranging Maximizes dynamic range without saturation; operates independently of ground intervention Scale factors, offsets, linearity, temperature compensation Verifies DC performance Uses GSFC 20’ Magnetic Test Facility Noise Verifies sensitivity via noise floor measurement Multi-layer mu-metal shield can Orthogonality Measures angles of Y and Z relative to X Ørsted and MAGSAT methods CAL step function Measures ADU with CAL on/off Useful for monitoring coarse changes Analog Housekeeping Verify 16 analog housekeeping channels Verifies voltages, temperatures, currents Heater operation Power delivered to heater, total circuit power vs. thermistor, heater monitor voltage Test with both sync on and sync off. Heater power verifications performed during sensor thermal vacuum testing.

Main Magnetometer Performance Metrics Selected Characteristics for the SPF MAGs that have been Measured During Calibration B = field in nT a = alignment s = scale factor c = ADC counts o = offset in counts and {1,2,3} == {x,y,z} Equation for MAG Sensor Model Parameter Calibration Test Calibration Product Comments Alignment Matrix Ørsted Method (“Thin Shell”) Alignment matrix A Symmetric portion only of the matrix MAGSAT Method Symmetric and asymmetric components Scale Factors Scale factors {s1, s2, s3} Referenced to Overhauser NMR standard; repeated measurements Temperature compensation A calibration used to flatten response to sensor temperature variations Offsets Simulated MAG rolls via offset spins fixture Offsets {o1, o2, o3} Multiple spins allow better differential analysis in noisier environments Long term offset stability (e.g., months/years) Reference detailed in-flight data over several years (e.g., MAVEN) Noise Laboratory mu-metal shield can over > 103 seconds Power spectral density (PSD) and RMS noise level RMS calculated from time series, PSD from FFT

MAG Calibration Measurements Summary We have demonstrated that the sensor conforms to MAG sensor model across all ranges and under all environments and for applied fields in all directions. Juno and MAVEN calibrations form the basis for the plan. They demonstrated facility accuracy and repeatability to few 10’s PPM in both orthogonality and scale factor. Accurate alignment to an optical cube reference on the sensor has been performed via MAGSAT method and compared to the Ørsted method. Anti-aliasing filter and frequency response characterizations have been performed. A series of calibrations pre/post vibration, pre/post thermal vac, pre/post EMI/EMC provide an extensive time history of end-to-end performance. Sensor vector accuracy exceeds system performance requirements. Additionally, it will likely be limited by spacecraft alignment mechanisms (e.g., boom) and spacecraft-generated in-flight fields. Gradiometry may aid in the reduction of these fields. A calibration report for FM-1 and FM-2 has been completed (LWS-MAG-RPT-0011)

MAG FM-1 and FM-2 Scale Factors The SPF MAG scale factors have been measured. Scale factors are confirmed in the MHA MAG Test Site using two GSM-19 Overhauser total field monitors as the facility reference. The design goal was to tune scale factors to within 1% of nominal values. The stated requirement is scale factor knowledge within 0.2% ± 1.0 nT. Repeated measurements show scale factor knowledge is consistent to a standard deviation of less than 0.01%. The measured performance exceeds requirements by at least an order of magnitude. Measured Scale Factors nT/ADU (nominal) FM-1 X Scale (measured) Y Scale (measured) Z Scale (measured) FM-2 Range 3 (65536 nT) 2 2.00021 2.00611 2.00392 2.00012 1.99753 2.00430 Range 2 (16384 nT) 0.5 0.49912 0.50094 0.50051 0.50097 0.49971 0.50198 Range 1 (4096 nT) 0.125 0.12495 0.12502 0.12501 0.12491 0.12517 Range 0 (1024 nT) 0.03125 0.03117 0.03121 0.03120 0.03132 0.03128 0.03136

MAG FM-1 and FM-2 Measured Zero Offsets Zero Offsets intrinsic to the MAG are the result of both electronics and sensor effects. Offsets have been adjusted in the electronics. MAG offsets were measured at the Test Facility via a series of rotations in a low field via a hodogram (ellipse fitting) technique. Since the spacecraft will provide a relatively large DC field at each sensor, this is not a substitute for on-the-spacecraft measurements. However, the results demonstrate the MAG dynamic range is nearly centered about zero. Sensor Axis FM-1 Measured Offset (1024 nT Full-scale range) FM-2 Measured Offset X -0.10 nT 0.38 nT Y -0.07 nT 2.55 nT Z -1.57 nT 0.42 nT 8

MAG Orthogonality The SPF FM-1 and FM-2 magnetometers have been repeatedly tested for orthogonality using both the MAGSAT Ørsted methods. This performance exceeds requirements. MAGSAT-derived Alignment Matrices

Noise Measurement MAG system noise is one metric of fluxgate performance. Noise was measured inside a mu-metal shield can to reduce environmental contributions (e.g., Earth field, 60 Hz, lab interference, etc.). Noise is below the 0.01 nT/sqrt(Hz) requirement. FM-1 and FM-2 have similar noise characteristics.

True Magnetic Field Vector MAG Error Estimate Summary (total error budget, referenced to nT, in the 1024 nT science range) Parameter Name Parameter Uncertainty (1 s, max.) Notes True Magnetic Field Vector {B1, B2, B3} - Alignment matrix (no temperature dependence) a matrix 0.35 nT repeatability of orthogonality at the 1024 nT full scale maximum (the low science range) Scale Factors (including temperature) {s1, s2, s3} 0.17 nT 0.005 nT/°C (1) scale factor uncertainty from calibration at 1024 nT (2) temperature compensation uncertainty Offsets {o1, o2, o3} 0.24 nT long term drift over ~ 2 years (via similarity to MAVEN flight data, 2013 - present) ADC uncertainty {c1, c2, c3} +/- 0.0078 nT +/- 0.015 nT/°C (1) quantization characteristic (datasheet) (2) temperature drift, max. (datasheet) RMS Noise 0.14 nT power spectral density at 292.9 samples/sec Error Summary (1) ε 0.48 nT Which is 0.047% of the 1024 nT full scale. Total error/uncertainty % is reduced for larger fields. Correlated errors sources are summed; uncorrelated sources have zero covariance and are ∴ RSS summed Offsets will necessarily need to be measured in-situ on the spacecraft in flight Errors from spacecraft AC and DC magnetic fields, boom deployment uncertainty, etc. are not included in this summary

SPF MAG PSR Summary The FM-1 and FM-2 MAGs have been designed, built, tested, and calibrated to GSFC standards. The MAG sensors have been vibrated prior to delivery to SSL. Some testing has been performed as part of the FIELDS suite testing. This has included MEP vibration, EMI/EMC, and thermal vacuum testing. FM-1 and FM-2 MAG testing has demonstrated the performance of the two instruments meet or exceed the requirements.

MAG Backup MAG Backup Slides

MAG Documentation Status Documents/Drawings Released in the GSFC CM System MAG has 101 documents and 72 drawings released in the CM system, https://ehpdmis.gsfc.nasa.gov (click on images above to expand PDF to view the lists)

MAG Sensor Coordinate System

FM1 & FM2: Measured Mass Summary The SPF FM-1 and FM-2 MAG masses has been measured. Total masses are within the FIELDS allocation. Masses represent measurements after final staking and coating. The harnesses are built at APL; these mass budgets are kept at a higher level. MAG Component FM-1 Measured (g) FM-2 Measured FIELDS Allocation per unit Sensor, cover, heater, and pigtail 365 366 641 Blanket (estimate) 360 50 Electronics board 355 381 Electronics frame 244 246 310 Total MAG Mass 1324 1327 1382

MAG Power Summary The SPF MAG power has been measured for each MAG The power is nearly identical. Both heater and analog electronics power are within allocation in the expected operational ranges. Power at temperature was measured during the Voltage, Temperature, and Frequency Margin tests. Analog Electronics -40 °C (mW) +23°C +80 °C FIELDS Allocation +12V rail 528 576 624 ↓ -12V rail 276 324 360 Total 804 900 984 940 Table 1: Analog Electronics Power AC Heater Electronics +24V Bus (W) +30V Bus +35V Bus Max. Power In 2.64 4.13 5.61 Max. Heater Authority 1.80 2.81 3.82 Power at -10°C 0.94 1.47 2.01 Power at -20°C 1.24 1.43 2.30 Table 2: AC Heater Electronics Power (FIELDS Allocation = 2W)

Sensor Thermal Balance Testing The MAG thermal team has performed multiple thermal balance tests using the EM sensor November 2014 December 2015 November 2016 These tests have been useful in understanding blanket performance & requirements, evaluation of blanket coatings, and heater power requirements. With the present blanket configuration, if the mounting interface temperature is > -130°C, the sensor temperature is expected to be greater than -15°C, which is within the flight heritage range.

MAG Level 5 Requirements (LWS-MAG-RQMT-0003) Number Level 5 Requirement Parent Traceability Verification Method Verified L5-MAG-01 MAG components shall be selected to withstand the environment of SPP for the duration of the mission as defined in the Environmental Design and Test Requirements Document, 7434-9039 L4-FIELDS-107 I Parts PCB @ 9/2013 and Environmental tests L5-MAG-02 Each MAG shall be a vector fluxgate magnetometer with 4 range settings per system, with nominal values of: 65,536 nT, +/- 2% (∆q = 2.0 nT) 16,384 nT, +/- 2% (∆q = 0.5 nT) 4,096 nT, +/- 2% (∆q = 0.125 nT) 1,024 nT, +/- 2% (∆q = 0.031 nT) where ∆q represents the nominal ADC bin size L4-FIELDS-104 D, T Calibration Report LWS-MAG-RPT-0011 L5-MAG-03 Each MAG shall have an absolute vector measurement accuracy calibrated to within 0.2% ± 1.0 nT L4-FIELDS-105 L5-MAG-04 The intrinsic noise level of the MAG sensor and electronics shall be less than 1x10-2 nT/sqrt(Hz) at 10 Hz T L5-MAG-05 Each MAG shall use the FIELDS-provided 4.8 MHz clock to initiate vector samples. Each sample shall be separated by 16384 periods of the 4.8 MHz clock, +/- 100 microseconds. L4-FIELDS-101 I, T VTFMT LWS-MAG-PROC-0008 L5-MAG-06 Each MAG shall generate a telemetry data message after the completion of 256 vector samples. L4-FIELDS-106 L5-MAG-07 The MAG electronics shall meet performance requirements after exposure to a total dose environment of 40 krads(Si). A Parts PCB 9/2013 L5-MAG-08 No single failure in the MAG electronics shall cause loss of data from both MAG sensors. IB, OB MAGs are independent L5-MAG-09 Each MAG shall provide a non-magnetic AC sensor heater controller to maintain the sensor temperatures above the required survival and operational temperature. L5-MAG-10 The MAG sensor heater controllers shall be powered independently of the MAG sensor electronics.

MAG Level 5 Requirements (LWS-MAG-RQMT-0003) Number Level 5 Requirement Parent Traceability Verification Method Verified L5-MAG-11 The MAG sensor AC heater controllers shall be compatible with the SPP Electro- Magnetic Environment Control Plan, 7434-9040. L4-FIELDS-101 T EMI/EMC testing L5-MAG-12 MAG samples shall be synchronized to the spacecraft clock via the FIELDS-provided 4.8 MHz clock. D, T LWS-MAG-PROC-0008 L5-MAG-13 The MAG data transmission modes shall comply with the FIELDS Interface Control Document. I L5-MAG-14 The MAG shall power up autonomously and in an operational mode, returning science messages at the rate specified the FIELDS Interface Control Document, SPF_MEP_100_CDI_ICD. I, T L5-MAG-15 The MAG shall survive the survival thermal limits and operate within the operational temperature limits as specified in the FIELDS Environmental Requirements Document, 7434-9039. L4-FIELDS-102 L5-MAG-16 The MAG shall meet performance requirements after exposure to static launch loads as provided in the FIELDS Environmental Requirements Document, 7434-9039. Vibration Testing L5-MAG-17 The MAG shall meet performance requirements after exposure to random vibrational loads as provided in the FIELDS Environmental Requirements Document, 7434-9039. L5-MAG-18 The total mass of the MAG sensors shall comply with the mass allocation per the FIELDS Interface Control Document, 7434-9055. Measured L5-MAG-19 The total mass of the MAG electronics cards and frames shall comply with the mass allocation per the FIELDS Mechanical Interface Control Document, SPP-MEP-MEC- 027. L5-MAG-20 The total MAG electronics orbital average power consumption shall comply with the power allocation per the FIELDS MAG Interface Control Document, SPF_MEP_103_MAG_ICD. L5-MAG-21 The MAG command formats shall comply with the FIELDS Interface Control Document, SPF_MEP_100_CDI_ICD.

Fluxgate Magnetometer Sensor Model An ideal magnetic sensor would produce an output vector in digital counts (c1, c2, c3) equal to a constant times the true ambient vector magnetic field, e.g., |B| = s |c| The MAG sensor is close to this ideal, in that the true vector magnetic field, |B|, is the product of an “alignment correction” matrix, |a|, and the scaled (s1, s2, s3) and zero-corrected instrument counts (c1, c2, c3): Where the a-matrix is nearly the identity matrix (an,m<< 1.0) and the scale factors (s1, s2, s3) are nearly unity. Our calibration and verification tests have been designed to verify that the sensor model applies across all instrument dynamic ranges and environments, and to determine the parameters of the sensor model. Quantization noise on (c1, c2, c3) from the LTC1604 ADC is +/- 0.5 LSB, or +/- 7.6 ppm. The temperature coefficient on the ADC adds an additional +/- 15 ppm/°C. The RMS sensor noise also adds < 0.1 nT RMS. Equation for MAG Sensor Model B = field in nT a = alignment s = scale factor c = ADC counts o = offset in counts and {1,2,3} == {x,y,z}

Long Term Offset Stability: MAVEN MAG Rolls Analyses Summary (in-flight measurements at Mars) MAVEN launched on 11/18/2013 and has been operating continually at Mars since 9/22/2014 in a low field (mostly below 500 nT). This has provided an opportunity to measure long-term offset stability throughout the mission via spacecraft rolls/slews. The SPP MAG fluxgate circuitry is based upon the MAVEN design. Long term stability of the MAVEN MAGs has been very good. StdDev per axis has averaged 0.14 nT, With a sensor total 1 s = 0.241 nT X Y Z Ave -0.317 -1.919 -0.935 Std Dev 0.124 0.143 0.149 Total Sigma 0.241 3* Sigma 0.722

MAG Scale Factor Temperature Compensation Measured over a range -75 °C to +30 °C with the EM With temperature compensation components installed, the MAG scale factors are very stable over wide temperature ranges. In the worst case of {X, Y, Z}, a > 100 °C temperature difference changed the scale factors by a total of < 0.09%. Since temperatures are monitored, even this small factor could be further reduced. 23

MAG Instrument Performance: Linearity Linearity is measured at the MAG Test Site in all four ranges. Errors versus full scale from measured data to best-fit line to the data are shown below. MAG linearity is excellent. X Y Z Hi Range 0.0021% 0.0029% 0.0081% Lo Range 0.0038% 0.0149% 0.0099% 24

SPP MAG Proportional Heater Output Varies and is Proportional to Sensor Thermistor Resistance At 30V bus, loss in steady state circuit = 185 mW; Switching losses = 375 mW; total 560 mW for losses on PCB. Complete details are found in LWS-MAG-ER-0002, SPF FM MAG Heater Characterization report.

GSE Delivered to SSL: SPF MAG Dummy Loads Dummy load simulates sensor load to drive and feedback circuits and allows safe operation of MAG electronics board without connecting sensor. There is one dummy load for each FM system. These have been delivered with the flight units. They are used both at the FIELDS level and also on the spacecraft. Pigtail length is the same as the flight sensors Mounts on boom with same footprint

End Item Data Packages are Complete Paper copies of the End Item Data Packages (EIDP) are complete and ready for delivery

GSFC Magnetic Test Site: Tests for Solar Probe Plus Calibration Standards and Accuracy Limits (1) The reference standard at the GSFC MAG Test Site is a GSM-19 Overhauser absolute field magnetometer (1). It is a nuclear magnetic resonance device operating utilizing the quantum physics of hydrogen atoms. The gyromagnetic ratio linearly relates proton oscillation frequency (Larmor frequency) to magnetic field magnitude and is a fundamental physical constant (2). The proton magnetometer is our facility reference standard and similar to those used around the world in national geomagnetic observatories. This is useful for measurements of the instantaneous field (at 1 Hz) and for calibration of the facility coil constants. We use two GSM-19 magnetometers at standard locations inside the coil system, one as the reference (“PP1”) and one as a verification of the reference (“PP2”). These magnetometers have a specified sensitivity of 0.022 nT at 1 Hz, a resolution of 0.01 nT, and an absolute accuracy of +/- 0.1 nT, over a range of 20,000 nT to 120,000 nT. An instrument data quality indicator verifies lock onto the precession frequency. Total errors associated with the proton precession magnetometers are << 10 ppm. For SPF, we performed our reference measurements at 50,000 nT. Lower field measurements (e.g., 1000 nT) are extrapolated from coil constants measured by the reference standard at 50,000 nT. http://www.gemsys.ca/products/rugged-overhauser-magnetometer/ http://physics.nist.gov/cgi-bin/cuu/Value?gammae

GSFC Magnetic Test Site: Tests for Solar Probe Plus Calibration Standards and Accuracy Limits (2) The coil system is 6 meters in diameter, or > 100,000X the loop area of a fluxgate bobbin. The field at the fluxgate is extremely uniform at the Test Site. Additionally, we align the sensor axes to the facility axes to ensure repeatable tests and minimized cross-field effects. The primary sources of AC noise at the Test Site include 60 Hz power/ground and 25 Hz (Amtrak). We address this by oversampling and averaging. For example, each measurement is a minimum of 10 telemetry packets, which represents 2560 vectors per measurement. Each proton measurement is also averaged during this period. The primary DC error sources include facility gradients and long-term offset drifts. We address DC offsets by performing differential measurements. For example, if we are measuring scale factors, we may apply +/- 15,000 nT and look at a total dB of 30,000 nT. The reduces the need for a stable offset to less than 60 seconds. The SPF MAG uses a 16-bit digitizer. Digitization error for a single sample is 1/65536 or 15 ppm. By oversampling the field at 292 Hz and averaging for 10 seconds, the improvement in signal to quantization error is increased by more than a factor of 100. Scale factors are known and repeatable. In tests run the first and second weeks of April, the repeatability of scale factors differences between different dates is <0.005%.