TRAnsit Characterization ExploreR Ground Systems and Mission Operations Jaime Esper / 592 10/31/2007 Technical & Management Review GSFC Competition Sensitive Ground Systems GSFC Competition Sensitive Ground System Requirements • Data volume per contact ~2.16 Gb, 5 contacts/day, total daily volume ~10.8 Gb • Playback 4.5 Mbps, S-Band QPSK (includes 17% CCSDS overhead and 30% contingency) • Transmission T1 line from Ground station to MOC • Uplink load commands once per week. Autonomous time-tagged commanding in the intervening • Capability for real-time commanding in emergencies and for targets of opportunity • Support ground autonomy to monitor downlinks, evaluate health and safety and alert on-call operations personnel GSFC Competition Sensitive TRACER MOC Characteristics • MOC at CfA – Colocated with Science Operations Center – Uses existing operations expertise – Shares infrastructure with Chandra – Connected to GSFC through T1/VPN for spacecraft I&T support GSFC Competition Sensitive TRACER MOC Architecture SSA TRACER 5 kbps tlm 2 kbps cmd TDRS MOC/SOC @CfA Critical Events Monitoring / Contingency Communications Mission Ops Center TLM, Eng/HK Wallops Alaska/ Svalbard/ LRO White Sands CMDs RT health/safety processing Commanding Mission scheduling Instrument data handling Trending/Analysis Orbit determination/control Mission planning Network & contact schedule S/C monitor/control Mission Ops testing Level 0/product processing/distribution Level 0 Data Archive CMDs@2kbps TLM, Eng/HK Level Zero Eng/HK Data Products White Sands Complex Coordination SOC Ops and Processing Legend: Eng= Engineering data HK=Housekeeping data CMD=Commanding TLM= Telemetry data Wallops Remote S/C support Observer Support Observation planning Science trending Data validation Calibration Level 1-3 processing GSFC Competition Sensitive CMD/TLM “Virtual” SOC Ground System Options/Characteristics • • • • • Leverage existing ground station network, including use LRO/White Sands complex Combine TRACER ops in existing ops facility SOC may be extended by several “virtual” stations around the country/world Level-zero processing done at MOC, and data delivered to SOC for further processing Use TDRSS link though White Sands for critical event coverage and/or contingency operations GSFC Competition Sensitive Mission Operations GSFC Competition Sensitive Basic Operations Timeline Week 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Launch and Early orbit Spacecraft/Instrument Checkout and Science Commissioning Normal Operations 8x7 2 to 4 years • Launch event coverage through L10-11 • Spacecraft telemetry through TDRSS after fairing separation • Critical Event coverage through TDRSS • Spacecraft commissioning and checkout 30-day allocation • Normal operations begin L+30 days. • Operations staffing around the clock for early phases of checkout, then back to 5 days per week, 8 hr shifts. GSFC Competition Sensitive Early Operations Timeline • Early on-orbit operations – Following separation (8 minutes after launch) ACS is automatically enabled in Initial Acquisition/Safehold mode – Deploy solar array – Control system points spacecraft such that solar array normal is pointed to sun (CSS, TAM, wheels, magnetic torquers) – ACS maintains the spacecraft in a power positive thermal safe attitude – Ground commands switch to normal mode – Focal Plane Aperture is Opened: First Light GSFC Competition Sensitive Normal Mode Operations Timeline • Turn on and check out instrument – – – – Assure bus & instrument have sufficient time to outgas (contamination) Instrument turn on Calibration maneuvers Determine offset between instrument boresight, guide telescope and ACS frames • • Nominal science mission starts – • User scripted inertial target attitudes In science mode – – – 3 Axis zero momentum FGS used for both attitude and rate Reaction wheels used for control – – Magnetic torquers used for unloading accumulated momentum Failure detection logic with backup safehold mode • • • Launch induced shifts PIID controller ~0.1 Hz bandwidth Weekly observation runs are event or time-triggered execution driven Observatory enters safehold when: – – – – – Sunlight detection threshold is violated Solar array current drops below threshold On-board computer re-sets Keep-alive signals are not received by the on-board computer (monitoring RW, MTB, CSS/FSS, Gyros, Instrument, TAM, FGS Signal) Spacecraft attempts recovery autonomously once, and then waits for ground commands if unsuccessful GSFC Competition Sensitive Eclipse Duration with Drag Effects • • Drag causes 6 AM orbit to enter constant shadow season after 3rd year Moving ascending node back to 5:30 AM and adjusting initial inclination to 97.45° will result in 4 full-Sun periods over a 4-year mission (baseline) 6 AM Nominal launch – Max Drag 5 AM Nominal launch – Max Drag 5:30 AM Nominal launch – Max Drag 6 AM Nominal launch – No Drag GSFC Competition Sensitive Lifetime Analysis • • • NASA Policy Directive (NPD) 8710.3 requires limiting orbit lifetime after mission completion to 25 years or maneuvering to an approved disposal orbit Analysis indicates that TRACER re-enters within 5 - 25 years from 550 km No propulsion system is needed for EOL decommissioning GSFC Competition Sensitive