THEMIS Operations & Anomalies

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 versus 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 per THEMIS SRR Note: The THEMIS spacecraft were designed to operate in 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 • BAU FSW memory corruption • 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

10. Instrument Anomalies

11. Anomaly Distribution versus Solar Cycle Anomalies per year: 5 7 7 11 11 14 14

12. Summary • THEMIS has been on-orbit since February 2007. • Primary mission was successfully completed in 2009. • Two probes were transferred to lunar orbits in 2009-2011. • Three probes continue to operate in Earth orbits. • Radiation belts are crossed twice daily in Earth orbits. • To date, 99 anomalies were seen across all 5 probes. • Of these, 70% appear to be related to space weather. • Anomalies often appeared after SWPC issued alerts. • Number of events increased with activity in solar cycle. • No permanent damage was seen so far. • The UCB operations team monitors space weather forecasts and alerts provided by NASA/GSFC and NOAA.