4 th NASA Space Weather & Robotic Mission Operations Workshop, NASA/GSFC, Greenbelt, MD, September 27, THEMIS Operations & Anomalies Manfred Bester Space Sciences Laboratory University of California, Berkeley Space Sciences Laboratory University of California, Berkeley

4 th NASA Space Weather & Robotic Mission Operations Workshop, NASA/GSFC, Greenbelt, MD, September 27, Overview THEMIS & ARTEMIS Mission Orbits Spacecraft Design Relevant Requirements Space Weather Related Anomalies Anomaly Distribution vs. Solar Cycle Summary

4 th NASA Space Weather & Robotic Mission Operations Workshop, NASA/GSFC, Greenbelt, MD, September 27, THEMIS Mission Orbits: 2007 – Probes in synchronized orbits with periods of 4, 2, 1, 1 and 4/5 days Conjunctions formed in magnetospheric tail every 4 days Launched on Feb. 17, 2007 Time History of Events and Macroscale Interactions during Substorms (THEMIS) NASA Medium-class Explorer Mission Managed in PI Mode by U.C. Berkeley

4 th NASA Space Weather & Robotic Mission Operations Workshop, NASA/GSFC, Greenbelt, MD, September 27, Extended Mission: Since 2009 Time History of Events and Macroscale Interactions during Substorms (THEMIS): 3 Probes (A/P5, D/P3, E/P4) in synchronized Earth orbits with ~1-day periods Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS): 2 Probes (B/P1, C/P2) departed Earth in 2009, lunar libration orbit phase in 2010/2011, in lunar orbits since 2011

4 th NASA Space Weather & Robotic Mission Operations Workshop, NASA/GSFC, Greenbelt, MD, September 27, Relevant Requirements REQUIREMENTSYSTEM DESIGN M-1. The THEMIS operational system shall be designed for at least a two year lifetime. Compliance. All flight systems are designed and analyzed for two year lifetime. Demonstrated on orbit M-3. THEMIS shall be designed for a total dose environment of 33 krad/year (66 krad for 2 year mission, 5mm of Al, RDM 2) Compliance. Radiation analyses performed. Performance Assurance and Implementation Plan (PAIP) THM_pa_001A.doc Version A-2003-Sept 30 Signed-Off. Demonstrated on orbit M-4. THEMIS shall be Single Event Effect (SEE) tolerant and immune to destructive latch-up. Compliance. Radiation analyses performed. Performance Assurance and Implementation Plan (PAIP) THM_PA_001A.doc Version A-2003-Sept 30 Signed-Off. Demonstrated on orbit M-5. To the maximum extent possible, THEMIS operational system shall be designed to be single fault tolerant and still meet minimum mission success criteria. Compliance. Single point failures, reliability and possible failure modes have been assessed through Fault Tree Analyses, PRAs, and preliminary FMECA. In addition, THEMIS is inherently single point tolerant by virtue of M- 6, constellation redundancy and use of on-orbit spare. Demonstrated on orbit M-6. THEMIS Probe 3 or 4 shall be capable of replacing any other probe during the minimum mission. Compliance. Replacement margin (>50%) has increased considerably since CSR with optimized mission design. Note: P3/P4 replacement of P1 does not have to take it through a second year (since minimum mission is obtained in one year). Forward runs for replacement strategies still to be completed. Demonstration on orbit was not required Note: The THEMIS spacecraft were designed for Earth orbits!

4 th NASA Space Weather & Robotic Mission Operations Workshop, NASA/GSFC, Greenbelt, MD, September 27, Spacecraft Bus & Instruments Fields and Waves Instruments (3) Fluxgate Magnetometer (FGM) DC and low-frequency magnetic fields Search Coil Magnetometer (SCM) AC magnetic fields Electric Field Instrument (EFI) Electric fields and waves Particle Instruments (2) Electrostatic Analyzer (ESA) Low-energy ions and electrons Solid State Telescope (SST) High-energy ions and electrons Stowed and Deployed Configuration Interior Layout of Probe Bus and Instrument Suite

4 th NASA Space Weather & Robotic Mission Operations Workshop, NASA/GSFC, Greenbelt, MD, September 27, Spacecraft Bus & Instrument Electronics Radiation Sensitive Electronics Spacecraft Bus General Dynamics ColdFire processor (8.388 MHz) SRAM for active code and data (512 kBytes) EEPROM for default FSW and parameters (512 kBytes) SUROM for initialization (16 kBytes) Bulk memory array (SDRAM, 64 MBytes) FPGA in Power Control Module (PCM) Instrument Suite Harris 80C85ARH processor (2.0 MHz) SRAM for active code and data, segmented and shared with FPGA (8x128 kBytes, Honeywell HX6228) NV memory for default FSW and parameters (8x128 kBytes, 28C011) Boot ROM (8x8 kBytes, Raytheon R29793) SSR (SDRAM, 256 MBytes) with periodic scrubbing for errors

4 th NASA Space Weather & Robotic Mission Operations Workshop, NASA/GSFC, Greenbelt, MD, September 27, Space Weather Related Anomalies Anomalies Likely Related to Space Weather Seen On-orbit Spacecraft Bus BAU processor warm or cold resets BAU processor communications losses with PCM FPGA BAU bulk memory scrub errors Instrument Suite IDPU processor resets IDPU SSR excessive ECC single or multiple errors IDPU LVPS over-current trips in Earth and lunar orbits

4 th NASA Space Weather & Robotic Mission Operations Workshop, NASA/GSFC, Greenbelt, MD, September 27, Spacecraft Bus Anomalies Relevant Spacecraft Bus Anomalies Encountered Since Launch ID ProbesAnomaly DescriptionOperational Impact Work-around / Mitigation Risk Level 11, 15, 18, 21, 31, 34, 36, 44, 47, 48, 54, 55, 57, 58, 63, 68, 71, 72, 73 THA: 3, THB: 0, THC: 2, THD: 7, THE: 7 BAU ColdFire processor warm and cold resets likely caused by SEUs 2007: 3x, 2008: 1x, 2009: 3x, 2010: 3x, 2011: 5x, 2012: 4x Engineering and science data loss; temporary service loss Run reset recovery procedures Low 9, 20, 22, 27, 33, 40, 41, 42, 43, 46, 51, 53, 67, 69, 75 THA: 1, THB: 1, THC: 1, THD: 10, THE: 2 BAU ColdFire processor loses communications with the PCM FPGA 2007: 1x, 2008: 3x, 2009: 1x, 2010: 6x, 2011: 1x, 2012: 3x Engineering and science data loss; temporary service loss Run recovery procedures that include forcing a BAU cold reset Low 24THE: 1BAU bulk memory scrub errors 2008: 1x Bad data in single or multiple memory cells Wait few days until problem subsides, or power cycle SSR otherwise Low A total number of 76 anomalies were seen to date across all five spacecraft. This amounts to 2.75 anomalies per spacecraft per year to date. About 67% of these may be related to space weather effects.

4 th NASA Space Weather & Robotic Mission Operations Workshop, NASA/GSFC, Greenbelt, MD, September 27, Instrument Anomalies Relevant Instrument Anomalies Encountered Since Launch ID ProbesAnomaly DescriptionOperational Impact Work-around / Mitigation Risk Level 52THC: 1IDPU processor reset and instruments went into safe mode 2010: 1x Instruments went into safe mode; few hours of instrument downtime and science data loss Ran reset recovery procedures Low 13, 19, 30, 35, 38, 49, 70, 76 THA: 0, THB: 1, THC: 5, THD: 1, THE: 1 IDPU SSR experiences errors in single or multiple memory cells 2007: 1x, 2008: 1x, 2009: 3x, 2010: 1x, 2011: 0x, 2012: 2x Bad data in single or multiple memory cells Wait few days until problem subsides, or power cycle SSR otherwise Low 28THD: 1IDPU LVPS over-current trip, likely caused by SEU in ETC FPGA 2008: 1x Instruments went into safe mode; few hours of instrument downtime and science data loss Power cycled IDPU and instruments Low 60, 61, 62, 64, 65, 66 THB: 1, THC: 5IDPU LVPS over-current trips near periselene passages 2011: 5x, 2012: 1x Instruments went into safe mode; few hours of instrument downtime and science data loss Closed attenuators in front of Solid State Telescope (SST) instrument around periselene Low

4 th NASA Space Weather & Robotic Mission Operations Workshop, NASA/GSFC, Greenbelt, MD, September 27, Anomaly Distribution versus Solar Cycle Anomalies per year:

4 th NASA Space Weather & Robotic Mission Operations Workshop, NASA/GSFC, Greenbelt, MD, September 27, Summary THEMIS has been on-orbit since February 2007 Primary mission successfully completed in 2009 Two probes transferred to lunar orbits Three probes continue to operate in Earth orbits Radiation belt crossings twice daily in Earth orbits UCB operations team monitors space weather Experienced space weather related anomalies Some anomalies appeared after SWC issued alerts Number of events increased with activity in solar cycle Flight operations team developed recovery procedures Minimal instrument downtime and science data loss No permanent damage seen so far