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THEMIS Operations & Anomalies

The THEMIS mission, launched by NASA in February 2007, consists of five probes studying substorm events in synchronized orbits around Earth and the Moon. This overview discusses mission orbits, spacecraft design, instruments, and relevant requirements. Key findings highlight the impact of space weather on spacecraft operations, with approximately 67% of identified anomalies related to these effects. The U.C. Berkeley operations team monitors anomalies, developing procedures to minimize downtime and data loss. The mission continues to yield significant insights into magnetospheric phenomena and solar cycle interactions.

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THEMIS Operations & Anomalies

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  1. University of California, Berkeley Space Sciences Laboratory THEMIS Operations & Anomalies Manfred Bester Space Sciences Laboratory University of California, Berkeley

  2. Overview • THEMIS & ARTEMIS • Mission Orbits • Spacecraft Design • Relevant Requirements • Space Weather Related Anomalies • Anomaly Distribution vs. Solar Cycle • Summary

  3. THEMIS Mission Orbits: 2007 – 2009 Time History of Events and Macroscale Interactions during Substorms (THEMIS) NASA Medium-class Explorer Mission Managed in PI Mode by U.C. Berkeley http://themis.ssl.berkeley.edu http://www.nasa.gov/themis 5 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

  4. 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

  5. Relevant Requirements Note: The THEMIS spacecraft were designed for Earth orbits!

  6. Spacecraft Bus & Instruments Interior Layout of Probe Bus and Instrument Suite Stowed and Deployed Configuration • 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

  7. 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

  8. 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

  9. Spacecraft Bus Anomalies 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.

  10. Instrument Anomalies

  11. Anomaly Distribution versus Solar Cycle Anomalies per year: 5 7 7 11 11 10

  12. Summary • 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

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