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This document provides a comprehensive overview of the THEMIS mission, including details on launch, instrument deployment, early orbit operations, coast phase maneuvers, orbit placement, science operations, probe configuration, data flows, and mission status. The text covers probe placements, coast phase operations, mission orbit placement challenges, data acquisition and recovery methods, including science data acquisition and processing. The document also highlights key achievements and the current status of the THEMIS constellation, showcasing the successful deployment and health of all five probes, as well as the functionality of their subsystems and instruments.
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THEMIS Constellation Operations • Dr. Manfred Bester • University of California at Berkeley • Mission Profile • Launch & Early Orbit Campaign • Instrument Deployment & Commissioning • Coast Phase • Mission Orbit Placement • Tail Season Science Operations • Constellation Status Summary
Launch Campaign at KSC • Delta II 7925-10 • 5 Probes in Fairing
Launch & Orbit Insertion • Launch: • Feb. 17, 2007 • Probe Release: L + 70 min • Responsibility for Constellation Operations Transitioned to U.C. Berkeley
THEMIS Mission Data Flows THEMIS Probe TDRS Berkeley Ground Station Wallops Ground Station KSC & Astrotech Merritt Island Ground Station (1) (3) Compatibility Test Van JPL I&T Facility UCB I&T Facility (3) White Sands Complex (3) Secure Intranet Santiago Ground Station Secure VPN Tunnel via Open Internet (2) GSFC NMC Open IONet Dial-up ISDN Line Berkeley Mission Operations Center Notes: Open (1), Restricted (2) or Closed (3) IONet Hartebeesthoek Ground Station Different Routes for End-to-end Data Flows Between Probes and GS Elements
Probe Placement Decision • Probe Placement Decision • Followed Initial Probe Bus and Instrument Check-out and Commissioning Operations on LD + 38 Days • Assigned Constellation IDs (P1−P5) to Probe Buses (A−E) THEMIS B −> P1 4 − Day Orbit THEMIS C −> P2 2 − Day Orbit THEMIS D −> P3 1 − Day Orbit THEMIS E −> P4 1 − Day Orbit THEMIS A −> P5 4/5 − Day Orbit • Decision Based on Probe Bus and Instrument Performance • Only Differences Noted Were in Telecom System – Strongest Performers (THEMIS B & C) Chosen for Largest Orbits • Coast Phase Orbit Set-up • Followed Probe Placement Decision • Maneuver Operations for THEMIS A−E to Rearrange Constellation into String-of-Pearls Configuration in 32-Hour Orbit • Interleaved with EFI Deployment Operations on THEMIS C−E
Coast Phase Orbit Placement Intermediate Orbits Towards Coast Phase Alignment
EFI Deployment • EFI Spin-plane and Axial Boom Deployment • THEMIS C (P2) Was Trailblazer • 13 Deployment Steps Plus Initial Spin-up to 20 rpm • Fortunately No Restrictions on Transmitter-on Times • Four Sets of Alternating Operations • Wire Boom Reel-out on X and Y Axes in 5-m Steps • Spin-up Maneuvers • Sensor Diagnostic Tests • Last Step Was Release of +Z and −Z Axial Booms • All Completed in 7 Working Days • THEMIS D (P3) & E (P4) Followed 3 Weeks Later • Performed Interleaved with Back-to-back Operations • Optimized On-console Staffing • Instrument and Mechanical Engineers for Boom Deploy Operations • Propulsion and Flight Dynamics Teams for Spin-up Operations • All Completed in 5 Working Days • THEMIS B (P1) & A (P5) Deployed After Mission Orbit Placement
Coast Phase Operations • Coast Phase Operations • Purpose of Coast Phase • Additional Mission Phase Inserted to Control Orbital Dispersions Prior to Mission Orbit Placement • Dayside Science Campaign in July and August 2007 • String-of-Pearls Orbit Configuration in 32-Hour Orbit • Instrument Characterization and Tuning • SST Attenuator Operations • EFI Bias Currents, Usher and Guard Voltages, Sensor Diagnostic Tests (SDTs) • Science Data Acquisition • Tuning of Science Trigger Algorithms • Usage of Predicted Magnetospheric Regions of Interest • Optimization of Acquisition and Recovery of Science Data Volumes
Mission Orbit Placement • Mission Orbit Placement • Very Complex Maneuver Operations Schedule • Frequent Rescheduling Required Due to Small Differences Between Predicted and Achieved Maneuver Performance • Also Needed to Work Around Tank Pressure Profile • Total Number of Thrust Operations • Including Entire Orbit Placement and All EFI Deployments: 170 4-Probe Conjunction on Wedding Day (Feb. 2, 2008)
Data Acquisition & Recovery • Science Data Acquisition • Science Data Acquisition Controlled via Predicted Crossings of Magnetospheric Regions of Interest and On-board Triggers • Slow Survey (SS), • Fast Survey (FS) • Particle Burst (PB) • Wave Burst (WB) • Science Data Recovery • Ground Station Passes • Primary Ground Station at U.C. Berkeley • Secondary Ground Station Support via NASA Ground Network and Universal Space Network • Tracking Schedule • One Pass per Perigee at High Data Rate for Data Recovery • Additional Tracking Passes Scheduled for Orbit Maintenance • Transition to Fully Automated, Lights-out Operations Almost Completed
Constellation Status Summary • Constellation Status Summary • THEMIS Mission Completed Almost One Year on Orbit • Currently in Primary Magnetospheric Tail Observing Season • All Five Probes Are Completely Deployed and Very Healthy • All Probe Bus Subsystems Performance Is Nominal • All Instruments Are Powered On and Function Nominally • All EFI Spin-plane and Axial Booms Are Deployed • All Five Probes Are in Their Primary Mission Orbits • Synchronized Orbits with Periods of 4, 2, 1, 1 and 4/5 Days • Attitudes Are Ecliptic North (3) and South (2) • Mission Operations Status • Ground Systems Are Functioning Well • Flight Dynamics Operations Are Almost Routine • THEMIS Web Site at UCB Contains More Information http://themis.ssl.berkeley.edu
