EFW Instrument Calibration

1. EFW Instrument Calibration John W. Bonnell Space Sciences Laboratory University of California, Berkeley

2. Overview • Why Calibrate? • Allows one to reliably operate the instrument on the ground and on-orbit. • Allows one to accurately interpret the science data produced by the instrument. • Allows one to verify that the instrument shall meet the measurement requirements flowed down to it. • How is EFW calibrated? • Board- and Mechanism-level testing/characterization: • SPB and AXB functional tests. • PRE, BEB, DFB, DCB, and LVPS Board-level tests. • System-level testing/characterization: • SciCal; Noise, Phasing/Timing; Full-Up. • Joint EFW/EMFISIS Interface Characterizations (aka. Playdates). • On-Orbit Testing and Characterization: • Sensor Diagnostic Tests (slow current- and voltage bias sweeps) to determine optimal on-orbit bias settings. • AXB Deploy and Trim operations to determine optimal differential AXB deploy lengths. • Intercalibration between E-field, plasma moments (Vi), B-field, and SC ephemerides (VSC) (E=-VxB) to determine effective antenna length.

3. EFW Calibration Flow Mechanism- and Board-Level Tests System-Level Tests Data Reduction • CTM: • IMONs • VMONs • Bit Flags • Etc. • On-Orbit Ops and Cals: • AXB Trim • SDTs • Intercalibration Data Analysis HSK Trending • Cal Par Files: • DC- Gain, Offset. • AC – Gain, Phase. • Cal Algorithms: • RAW->PHYS.

4. Component-Level Tests • SPB and AXB Functional Tests: • Deploy rates (cm/s as function of deploy length). • Deploy stroke (cm/click as function of deploy length). • Actuator firing times and power (time-to-actuate and current as function of supply voltage and temperature). • PWA-Level Functional Tests: • Current consumption (current at nominal supply voltage as function of temperature -- All). • DC- and AC-Response (analog gain, offset, phase; ADC/DAC calibrations, digital time delays, compression/decompression verification – BEB, DFB). • IMON and VMON gain and offset (LVPS). • Actuator control (power, status) readbacks (LVPS, DCB). • HSK gain and offset (DCB).

5. Component-Level Tests(Example Data) • BEB Frequency Response. • DFB Digital Filter Response. • Etc.

6. System-Level Tests • Electrical Functional Tests: • Science Calibration (SciCal): • IBIAS calibration (BIAS DAC to IBIAS). • DC Calibration: • VSPHERE, VGUARD, VUSHER as function of VSENSOR and DAC setting. • DAC HSK readback as function of DAC setting. • AC Calibration: • VSPHERE, VGUARD, VUSHER, EMFISIS voltage gain and phase shift relative to VSENSOR and VSPHERE for three sensor terminations (in Faraday Box with P-SIM; Box grounded or driven; P-SIM bypassed). • Noise, Phasing/Timing: • Noise floor as function of frequency for EMFISIS E-field I/F. • Verify end-to-end digital time delay for E, V, MSC, and MAG channels at nominal rates. • Full-Up Test: • Direct verification and calibration of medium- and large-amplitude end-to-end instrument response under nominal biasing conditions. • Joint EFW/EMFISIS Interface testing (aka. Playdates): • Characterize/verify polarity, gain, phase, dynamic range, noise floor and impulse response.

7. System-Level Tests(SciCal - Bias) • Sensor grounded via known resistance (Rs, 79.8-Mohm; << Rin). • BIAS DAC commanded via EFW GSE and SCE. • IBIAS sourced or sinked to sensor by BEB BIAS driver, driving sensor potential to VSENSOR = IBIAS*Rs. • VSENSOR measured using high-input impedance DMM. • VSENSOR • Linear regression of sensor bias current (IBIAS) against BIAS DAC setting or BIAS HSK readback, to estimate gain and offset, as well as residuals of data-model.

8. System-Level Tests(SciCal - DC) • Sensor driven via low-impedance voltage source (+/- 223 V). • USHER and GUARD DAC commanded via EFW GSE and SCE. • VSPHERE, VUSHER and VGUARD measured using high-input impedance DMM (3-Gohm). • Linear regression of output voltage against VSENSOR and BIAS DAC setting, and GUARD and USHER offset voltage against or HSK readback, to estimate gain and offset, as well as residuals of (data-model).

9. System-Level Tests(SciCal - AC) • Sensor driven via finite-impedance voltage source (plasma simulator, P-SIM: 79.8-Mohm || 8.9-pF). • Sensor deployed in Faraday Box (FBOX); box either grounded, driven, or grounded, with P-SIM bypassed to allow estimation and removal of sensor-to-box coupling effects. • VSPHERE, VUSHER, VGUARD and EMFISIS buffer outputs measured using high-input impedance O’scope (1-Mohm); finite output impedance of GUARD and USHER drivers affects absolute magnitude of measured gain. • Gain and phase relative to VSENSOR and VSPHERE computed, tabulated, and plotted.

10. System-Level Tests(Noise) • Sensors terminated to ground either via P-SIM or low-impedance (few ohm). • Both pairs of SPBs in FBOXes; AXBs in cradles on lab bench – allows effect of termination impedance and ambient noise to be observed. • Output of EMFISIS buffers through EMFISIS E-field I/F simulator measured using spectrum analyser. • Tabular and numerical data recorded using SOFTPlot utility. • Data recorded and shown on following plots in dBm (dB mW into 50-ohm load) – conversions to (V/m)2/Hz are as follows: • 0-12 kHz, 150-Hz BW, 100-m antenna: -100 dB mW is equivalent to 3.3*10-18 (V/m)2/Hz. • 0-500 kHz, 73-Hz BW, 100-m antenna: -100 dB mW is equivalent to 6.8*10-18 (V/m)2/Hz. • Noise characterization shows significant margins (10 to 40 dB) between continuum noise floor and sensitivity specification (noise floor at S/N=1), similar to those measured on the EFW ETU.

11. System-Level Tests(Noise, con’t) • FM2, X-Axis (U-Axis in Science Coordinates). • SPBs in FBOXes, terminated to signal ground with P-SIM, FBOX grounded. Ambient noise (GSE, etc.) EFW LVPS Lines 3*10-14 (V/m)2/Hz at 1 kHz 3*10-17 (V/m)2/Hz at 100 kHz

12. System-Level Tests(Phasing/Timing) • EFW Sensors driven via low-impedance voltage source or hard-grounded to signal ground. • EFW MAG and MSC interfaces driven through MAG and MSC I/F simulators. • IDENTICAL triggered tone burst signal applied to selected inputs (typ. V1, V3, V5; MAG_U, MAG_W; MSC_U, MSC_W) at known MET. • EFW Waveform (Survey, Burst1 and Burst2) TM collected. • Data time-tagged and plotted using EFW near-real time analysis tool (IDL/EFWPLOT). • Relative and absolute time delays of each channel and APID computed and compared to model based on FSW and DFB design and testing.

13. System-Level Tests(Phasing/Timing con’t) • Tone burst of 4 cycles of 10-Hz sine wave applied at 2010-12-06/21:23:05. • Sampled at 32 samp/s (SVY), 512 samp/s (B1), and 16384 samp/s (B2). • Absolute time delays as expected from DFB and FSW time tagging delays.

14. System-Level Tests(Phasing/Timing con’t) • Same as preceding, by shorter time scale (0.1 s, rather than 0.5 s), zooming in on relative delay of higher-rate channels (B1 and B2).

15. System-Level Tests(Full-Up Test) • Same configuration as NOISE test; allows effect of IBIAS on DC offset and differing sensor coupling on AC response to be observed. • IDENTICAL medium- to large-amplitude sinusoids with significant (tens of volt) DC offsets applied to selected EFW sensors (typ. V1, 3, 5; or V1 alone) while EFW commanded to realistic current-/voltage-biasing state. • EFW Waveform (Survey, Burst1 and Burst2) TM collected. • Analog data from representative channels collected (VSENSOR, VSPHERE, etc.). • Waveform data processed and analysed using EFW near-realtime tool (IDL/EFWPLOT).

16. System-Level Tests(Full-Up Test, con’t) • V1 and E12 have realistic amplitude and clean response that will be seen on-orbit (P-SIM in circuit). • Others channels show expected slew rate limiting due to finite floating ground driver BW (500-Hz) and finite preamp rails (+/- 15V). • Crosstalk ~0.1%. • 40-Vpp (400-mV/m equiv.), 1-kHz, -40-V DC offset. • Large-amplitude whistler test.

17. System-Level Tests(Full-Up Test, con’t) • 100-Vpp, 1-Hz, -40-V DC offset. • Large-amplitude crosstalk test (e.g. perigee pass –VxB removal). • Crosstalk ~ 0.1%.

18. System-Level Tests(EFW-EMFISIS I/F Survey, or Playdates) • Similar configuration to NOISE or SciCal, depending upon venue. • EMFISIS MSC and MAG sensors in shielded, three-axis coil stimulus boxes. • IDENTICAL signals (sinusoids, time bursts) applied to selected EFW and EMFISIS sensors.(typ. V1, 3, 5; or V1 alone) while EFW commanded to realistic current-/voltage-biasing state. • EFW Waveform (Survey, Burst1 and Burst2) TM collected. • EMFISIS TM collected. • Analog data from representative channels collected (VSENSOR, VSPHERE, etc.) to verify amplitudes, polarities, etc. • Waveform data processed and analysed using EFW near-realtime tool (IDL/EFWPLOT). • Sanity check of expected polarities, gains, phase shifts, noise levels.

19. On-Orbit Calibration • On-Orbit Testing and Characterization: • Sensor Diagnostic Tests (slow current- and voltage bias sweeps) to determine optimal on-orbit bias settings. • AXB Deploy and Trim operations to determine optimal differential AXB deploy lengths. • Intercalibration between E-field, plasma moments (Vi), B-field, and SC ephemerides (VSC) (E=-VxB) to determine effective antenna length.

20. On-Orbit Calibration(Sensor Diagnostic Tests, or SDTs) • Sensor Diagnostic Tests (SDTs or Slow Sweeps): • Slow current- and voltage bias sweeps to determine optimal on-orbit bias settings in different plasma regimes. • Each axis swept separately, with bias settings constant for one spin period. • Normal Survey mode E and V waveform telemetry used to record variation in swept and non-swept sensor potentials and differential potentials (apparent E-fields). • Ground processing (spin fits, manual inspection and interpretation) used to determine optimal (minimal offsets, minimal variation with environmental conditions) bias schemes. • EFW instrument has provisions for four on-board biasing tables (sunlit/eclipse; low-/high-density), to be controlled via time-tagged commands based on SC ephemerides and models/experience with plasma boundaries.

21. On-Orbit Calibration(SDTs, con’t)

22. On-Orbit Calibration(AXB Deploy and Trim Ops) • AXB Deploy and Length Trim Operations: • Slow current- and voltage bias sweeps to determine optimal on-orbit bias settings in different plasma regimes. • Each axis swept separately, with bias settings constant for one spin period. • Normal Survey mode E and V waveform telemetry used to record variation in swept and non-swept sensor potentials and differential potentials (apparent E-fields). • Ground processing (spin fits, manual inspection and interpretation) used to determine optimal (minimal offsets, minimal variation with environmental conditions) bias schemes. • EFW instrument has provisions for four on-board biasing tables (sunlit/eclipse; low-/high-density), to be controlled via time-tagged commands based on SC ephemerides and models/experience with plasma boundaries.

23. On-Orbit Calibration(AXB Deploy and Trim Ops, con’t) • Axial E field offset and spacecraft potential waveforms through full orbit and various plasma regimes (magnetopshere, plasmasphere) measured using normal Survey E and V waveform data. • Estimate of required change in axial boom stroke made using model of SC potential structure (simple offset monopole or dipole). • Additional stroke of one or both AXBs commanded during AXB trim ops period. • Further data collection and iteration to refine trimmed length, as needed or warranted.

24. On-Orbit Calibration(Intercalibration, E = -VxB) • In quiet conditions, away from boundaries, E = -VixB. • Systematic errors (differential photocurrents, antenna shorting factor) lead to offsets and reduction in magnitude of measured E. • On-orbit measurement of E (EFW),Vi(ECT-HOPE or SC ephem), and B (EMFISIS-MAG) allow estimation of offsets and gains and inclusion in CAL PAR files and algorithms. • Algorithms will use normal Survey E and V waveform data, along with analogous products from ECT-HOPE and EMFISIS-MAG.

25. Calibration Summary • Testing of end-to-end functionality of both EFW FM1 and FM2 complete. • Results show capabilities meet or exceed measurement requirements, as well as EFW science team goals. • All procedures and notes logged to FM Travelers to become part of EIDP. • Raw instrument and GSE data, along with supporting data reduction, analysis and reports stored (or to be stored on) or EFW SVN site and backed up. • EFW ETU provides hi-fi analog, digital, and software testbed for further testing, if needed. EFW FM1 and FM2 Calibration at the Instrument, Pre-Environmental Level complete, and both instruments ready to proceed to Environments.

26. BACKUP SLIDES

27. System-Level Tests(SciCal – AC phase) • Sensor driven via finite-impedance voltage source (plasma simulator, P-SIM: 79.8-Mohm || 8.9-pF). • Sensor deployed in Faraday Box (FBOX); box either grounded, driven, or grounded, with P-SIM bypassed to allow estimation and removal of sensor-to-box coupling effects. • VSPHERE, VUSHER, VGUARD and EMFISIS buffer outputs measured using high-input impedance O’scope (1-Mohm); finite output impedance of GUARD and USHER drivers affects absolute magnitude of measured gain. • Gain and phase relative to VSENSOR and VSPHERE computed, tabulated, and plotted.