THEMIS MISSION PRE-SHIP REVIEW “Our Gateway to the Cape…” The Electric Field Instrument (EFI)

1. THEMIS MISSION • PRE-SHIP REVIEW • “Our Gateway to the Cape…” • The Electric Field Instrument (EFI) • John Bonnell • University of California - Berkeley

2. Outline • Summary of EFI Status at Mission PSR • Final Test and Cal Results vs. Requirement Fulfillment • PFRs and RFAs since MPER.

3. EFI Status at Mission PSR • All PFRs closed out (see PFR Status for details). • All RFAs from previous reviews closed out or responded to (see RFA Status for details). • EFI on all five probes performing in-spec and in-family; all requirements fullfilled.

4. Mission Requirements Fulfillment • EFI Mission Requirements Fulfillment: • F1 through F5 Mission Requirements fulfillment noted in THEMIS Verification Matrix (see MSE Presentation). • Integrated EFI and component parts compliant with mission requirements.

5. Results of Performance Testing • DC and AC Transfer functions agree within Flight sets to better than 1 % on non-critical functions (USHER, GUARD, AC SENSOR gain, etc.), and better than 0.2 % on critical, matched functions (BIAS, DC SENSOR gain). • Full 16-bit control of all bias functions demonstrated (control to better than 1 part in 1000, as per MRD). • V- and E-channel gains on DFB as per specification. • DFB Spectral (Filter Bank, FFT, and AKR) and Derived Quantities data products as per specification. • Noise, DC Functional, AC Functional, and DAC Test results consistent, in-family and in-spec across all probes and throughout environmental testing (see Bonus Materials for example performance test outputs).

6. PFR & RFA Status (1) • New PFRs pertaining to EFI since Mission PER: • PFR-181, F3 EFI IMON Instability (also MPER RFA-2). • PFR-183, F3 AXB V6 Functional Test Anomaly. • PFR-206, F4 AXB Temperature Sensor Reading Anomalously (1052 C). • RFAs pertaining to EFI: • MPER RFA-2, Monitoring for Excess Current on EFI Instrument.

7. PFR & RFA Status (2) • PFR-183, F3 AXB V6 Self-Test Anomaly • During Mission I&T, the V6 channel of the F3 EFI responded anomalously during DC and AC Functional Tests. • Anomalous response traced to portion of internal test circuit, rather than EFI sensor functionality (ACTEST line connection). • Anomalous response is understood and repeatable, and so does not affect ability to determine state-of-health on-orbit. • Further diagnosis and re-work would require significant disassembly of core spacecraft structure and sub-systems (AXB tube; RCS; etc.), and would engender significant additional risk. • MGSE used during JPL testing to ensure consistent response in functional tests. • Unit will be flown AS-IS.

8. PFR & RFA Status (3) • PFR-206, F4 AXB Temperature Sensor Reading 1052 C • The AXB temperature sensor on F4 began to respond anomalously in a post-vibe LPT at JPL(1052 C at ambient; probe not obviously on fire or melting). • Anomalous reading corresponds to open condition on temperature sensor, based on bench tests with F6 Flight Spare. • By design and construction, open condition poses no threat to operation of EFI: • Open circuit on temperature sensor does not affect functionality of EFI sensor. • Temperature sensor is physically isolated from EFI Preamp. • Supply lines for temperature sensor electrically isolated from EFI Preamp. • Open circuit poses no risk to sensing circuit or HSK on BEB. • Loss of AXB temperature sensor does not affect ability to calibrate and operate the EFI on F4 on-orbit. • Further diagnosis and re-work would require significant disassembly of core spacecraft structure and sub-systems (AXB tube; RCS; etc.), and would engender significant additional risk. • Unit will be flown AS-IS.

9. PFR & RFA Status (4) • EFI Current Consumption (PFRs 096 and 181, MPER RFA-2) • Floating supply current consumption of EFI during ambient functional tests has shown marked variability over time and between axes and probes (up to a factor-of-two increase over nominal). • This variability does not occur during TVAC testing, and thus is not expected to occur during on-orbit operations. • Performance of EFI as measured by normal functional testing and more detailed case studies remains in-spec and in-family over time and between axes and probes. No oscillation or other malfunction of preamps seen during episodes of increased current consumption. • Excess current consumption amounts to 1-2 mA/preamp/supply, and represents no threat to LVPS floating supplies, either through voltage droop or excess loading (supplies handle 4x nominal current without significant droop). • Uptake of moisture by hygroscopic preamp PWB material (Thermount) and resulting high-impedance (>30-kohm) leakage path in PWB now most likely source of increase current consumption. • Further diagnosis and re-work would engender significant additional risk due to disassembly, invalidation of testing, etc. • Increase current consumption not expected to occur on-orbit, and does not affect EFI or LVPS performance, so units will be flown AS-IS.

10. PFR & RFA Status (5) TVAC currents are nominal

11. Bonus Content

12. EFI IMON by Probe, Axis, and Test Type

13. Example Performance Test Data –Housekeeping (APIDs 404 and 406) 404 – SOH1 HSK

14. Example Performance Test Data –Housekeeping (APIDs 404 and 406) 406 – SOH2 HSK

15. Example Performance Test Data –Spectral (APIDs 440, 44D and 44E) 440 – Filter Banks

16. Example Performance Test Data –Spectral (APIDs 440, 44D and 44E) 44D – PtclBurst FFT

17. Example Performance Test Data –Spectral (APIDs 440, 44D and 44E) 44E – WaveBurst FFT

18. Example Performance Test Data –DC Functional (Waveform V and E) 441, 443 – Fast Survey V and E

19. Example Performance Test Data –DC Functional (Waveform V and E) 445, 447 – Ptcl Burst V and E

20. Example Performance Test Data –DC Functional (Waveform V and E) 449, 44B – Wave Burst V and E

21. Example Performance Test Data –AC Functional (Waveform V and E) 449, 44B – ACTEST, evens.

22. Example Performance Test Data –AC Functional (Waveform V and E) 449, 44B – ACTEST, odds.

23. Example Performance Test Data –DC and AC Functional (449, 44B) 449, 44B – Noise, DC & AC Functional.