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University of California, Berkeley. Space Sciences Laboratory. THEMIS Operations & Anomalies. Manfred Bester Space Sciences Laboratory University of California, Berkeley. Overview. THEMIS & ARTEMIS Mission Orbits Spacecraft Design Relevant Requirements Space Weather Related Anomalies
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University of California, Berkeley Space Sciences Laboratory THEMIS Operations & Anomalies Manfred Bester Space Sciences Laboratory University of California, Berkeley
Overview • THEMIS & ARTEMIS • Mission Orbits • Spacecraft Design • Relevant Requirements • Space Weather Related Anomalies • Anomaly Distribution vs. Solar Cycle • Summary
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
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
Relevant Requirements Note: The THEMIS spacecraft were designed for Earth orbits!
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
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
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
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.
Anomaly Distribution versus Solar Cycle Anomalies per year: 5 7 7 11 11 10
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