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Face to Face Meeting

Face to Face Meeting. Session Topic: LAT Operating Modes Date: March 19 Time: 13:30 Convener: Scott Williams Objectives: Collect, sort out, and distribute information as needed Work with those who have worked on the issues and review from a system point of view

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Face to Face Meeting

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  1. Face to Face Meeting • Session Topic: LAT Operating Modes • Date: March 19 • Time: 13:30 • Convener: Scott Williams • Objectives: • Collect, sort out, and distribute information as needed • Work with those who have worked on the issues and review from a system point of view • Identify issues and propose plan for resolution

  2. Mission Operations Architecture LAT Instrument Operations Center LAT data handling LAT performance Standard product processing Alerts TDRSS GLAST Five contacts per day Routine Data and commands LAT Data Command Loads Status Standard products Schedule requests Malindi White Sands Science Support Center Science scheduling Archiving Guest Observer Support Standard product processing Spacecraft, IOC, and GBM data Mission Ops Center Observatory safety Spacecraft health Commanding Mission scheduling Instrument data handling Alerts Large loads Target of Opportunity Commands Schedules Level 0 data for archiving Standard products Schedule requests GBM Instrument Operations Center GBM data handling GBM performance Standard product processing GRB Coordinates Network Burst and transient Alerts GBM Data Status Command Loads

  3. GLAST Mission Phases • Launch Data – March 2006 • Phase 0 - Launch & early orbit: up to 60 days • S/C configuration and checkout: 10 days • LAT responsible for LAT thermal control using survival power bus • LAT turn-on, configuration, and checkout: 20 days • Subsystem checkout • Initial on-orbit calibration and alignment • LAT commissioning – 30 days • Science observation modes exercised and instrument response functions established • Phase 1 – Verification and Sky Survey: 12 months • LAT science verification • up to 20% of observing time for LAT calibration and test • Phase 2 – Science Observations: minimum 4 years • Peer review driven investigations • 5% observing time for LAT calibrations and maintenance

  4. Mission Operations • Routine operations • All sky survey for first year • Pointed observations in subsequent years • Minimal pointing constraints • Health and safety check of observatory • Real-time operations • Gamma ray Burst Alerts • Current observation autonomously interrupted for selected burst • Bursts observed for 5 hours then returned to interrupted observation • Transient detection alert • Anomaly alert • Target of Opportunity • Downlink volume • ~28 Gb per day

  5. LAT Operations Concept • LAT science operations • Driven by goals of the mission, which require the LAT to detect celestial gamma rays, discriminate charged particles, and maintain high observing efficiency • Nominal orientation is zenith pointed • Avoid obstructing the FOV of the LAT, and avoid the albedo gamma rays from cosmic-ray interactions in the upper atmosphere • ‘Rocking’ about this orientation will be standard, to make the coverage of the sky more uniform • Inertially pointed observations and hybrid ‘pointed scan’ mode will also be employed • Event data, after onboard background rejection, is accumulated in SSR • Rejection filters from few kHz rate to ~30 Hz • Retain candidate gamma rays and cosmic rays useful for calib.

  6. LAT Operations Concept (2) • Space-to-ground communications • Five daily downlinks scheduled for Malindi at 15 Mbps • Average data rate will be ~300 kbps for the LAT • Alerts will be transmitted via TDRSS DAS through the WSC ground stations to MOC • Data rate is low (~1 kbps) but message length is short • Low latency is vital: initial information about science transients (GRBs, AGN flares, etc.) detected by GBM or LAT, or onboard anomalies generated by the S/C or instruments • Ground-to-space communications • Command uploads (via S-band, 2kbps) - ~weekly • Calibration table uploads (S-band, 2kbps) - infrequently • Flight software uploads (via TDRSS MAS, 4kbps) - very infrequently • ToO commanding (TDRSS MAS, 4kbps) - infrequent

  7. GLAST Science Data Flow 28 Gbits/day 1 GBM 1 Spacecraft 26 LAT GBM Ops & monitoring Level Zero Processing 5 contacts/day 6-7 minutes each 15 Mbps Real time GBM H&S Recorded GBM Data Real time or playback S/C (as requested) GBM processing S/C Health & Safety GBM Instrument Operations Center Real time Housekeeping Recorded spacecraft Recorded GBM data Recorded LAT data Malindi Mission Operations Center Real time LAT H&S Recorded LAT Data Real time or playback Spacecraft (as requested) Spacecraft Level 0 GBM level 0 GBM Level 1 GBM standard products • Send real time housekeeping to IOCs • Buffer playback data and send as bandwidth allows • Oldest data typically <1 day old when received at MOC • Ground station saves data for at least seven days; MOC can request retransmission within that time. LAT performance monitoring Higher level Processing Archiving Data Distribution LAT level 0 LAT Level 1 LAT standard products LAT level 0 verification Science Support Center LAT level 1 and higher Level processing LAT Instrument Operations Center

  8. Schedule and Command Data Flows TDRSS 0.4 to 4 kbps White Sands GLAST Schedules Acquisition data Large Loads Target of Opportunity Commands GBM Scheduling GBM instrument S/W GBM Command Generation Command Loads GBM S/W Loads Spacecraft Command Generation Load Integration and Formatting Ground Station Scheduling Planning Data 5 contacts/day 2 kbps As-flown timeline Commands GBM Instrument Operations Center Schedules Acquisition data Mission Operations Center Target of Opportunity Request Instrument Activity Schedule Malindi As-flown timeline Command Loads LAT S/W Loads GBM Schedule Request • S-band, 2kbps • Command uploads - ~weekly • Calibration table uploads - infrequently • TDRSS MAS, 0.5 to 4kbps • ToO commanding - infrequent • Flight software uploads - very infrequently As-flown timeline LAT Scheduling LAT instrument S/W LAT Command Generation Instrument/Science Scheduling Target of Opportunity Selection LAT Schedule Request LAT Instrument Operations Center Science Support Center

  9. GLAST Alert Data Flows TDRSS • When LAT, GBM, or S/C decide to issue an alert (ideally science related), data will be downlinked via TDRSS DAS to White Sands then on to the MOC • Alert processor must be located in facility with high availability - MOC • Latency of 14 seconds includes 7-10 seconds to lock onto DAS • GBM generates coordinates onboard; Algorithm in alert processor will provide more accurate estimate MOC will distribute GRB-related information to GCN • MOC will also pass LAT-related data to the IOC GLAST 1 kbps for up to 5-10 minutes White Sands Latency from spacecraft to MOC less than 14 seconds Alerts GCN LAT Alerts Reformat Sorter LAT IOC LAT Data GBM Alerts Process Safety Alerts Alert Processor GBM IOC GBM Data Attitude Maneuver Notification Mission Operations Center

  10. Safe Mode Software Mode Safe Mode Recovery Hardware Mode Survival Mode GLAST Observatory Operational Modes • Launch • Early Orbit • Observatory Verification • Safe • Software • Hardware • Survival • Recovery • Standby/Engineering • Normal Operations • Re-entry Standby/ Engineering Mode Launch Mode Early Orbit Mode Observatory Verification Mode Normal Operations Mode Re-entry Mode

  11. LAT Operating Modes • Science Observing Modes - Standard, GRB, and Solar Flare (TBR) distinguished by trigger criteria and post-trigger filtering. • Standby Modes • Ready - Subsystems configured and ready to start nominal observing. • Engineering - Used for flight software update, parameter changes, subsystem configuration changes, and engineering tests. • Calibration - Raw L1T data collection and other subsystem calibrations which impact science observing efficiency or LAT dead time. • SAA Mode - Safing of ACD for South Atlantic Anomaly (SAA) passage. • LAT Power Up and Safe Modes • Detectors On - All detector subsystems powered on and housekeeping active. • T&DF On - LAT T&DF powered on, configured, and housekeeping active. • LAT Hardware Safe Mode - SIU powered, performing thermal monitoring and control(TBR), and providing housekeeping. All S/C interfaces active. • LAT Survival Mode - LAT powered off and performing thermal control with survival heaters. Temperatures are stable, no duration in mode time limit. • Pre-deploy Mode - Launch and early orbit mode. LAT powered off, radiator heaters active. LAT thermal environment is not stable and transition to Survival Mode must be made within TBD time constraint. • LAT Off - Pre-launch and re-entry mode, LAT and survival bus power off.

  12. LAT Operating Mode Transitions • Power up sequence is a progression through the defined LAT modes. • LAT Off • LAT Pre-Deploy • LAT Survival • LAT Hardware Safe • T&DF On • Detectors On • Ready • Observing Mode

  13. Correlation of LAT and S/C Modes LAT Safe Modes entered based on S/C action • S/C Software Safe Mode / LAT Ready • inhibit triggering and data transfer to SRR • S/C Hardware Safe Mode / LAT Hardware Safe • power down detectors and T&DF, but keep SIU operational to provide housekeeping • S/C Survival / LAT Survival • power down LAT and rely on survival heaters

  14. Background Material

  15. Mission Operations Overview • Launch Date: March 2006 • Mission Life: 5 year required with 10 year goal • Orbit: 450 to 550 km circular orbit, 28.5° inclination. • Spacecraft: RSDO spacecraft, to be selected ~summer 2002. • Mission Operations Center: TBD, to be selected ~spring 2003. • Ground Link: Ground Station (Malindi) – Five contacts per day to dump the bulk science data. Data volume is 28 Gbits per day. Downlink rate is 15 Mbps (TBR) over an X-band link. 32 kbps S-band downlink for real time housekeeping telemetry. Command uplink is 2 kbps • Space Link: Space Network – Demand Access System (DAS, 1 kbps) used for gamma-ray burst alerts, health and safety alerts, and other science and housekeeping functions. Single Access Service (SAS, 4 kbps) used for large command uploads and early orbital operations. Multiple Access Service (MAS, 500 bps) used for TOO commanding. • Operations Constraints: Earth limb avoidance, radiator, and solar panel pointing constraints. Spacecraft may autonomously adjust its operation (including its pointing) in response to a gamma-ray burst.

  16. Definitions • Alert • Packetized data transmitted by the spacecraft in response to a transient event. Alerts can be generated by instrument or spacecraft subsystems in response to the detection of anomalies or by the science instruments in response to transient scientific phenomena. • Phase • Time period in mission characterized by unique operating modes or constraints. • Mode • A specific configuration and set of operations or behavior that accomplish a specific purpose and impact the LAT to S/C interface. • Observing Efficiency • Fraction of time available that is spent acquiring data. On the GLAST mission the time available is the time on orbit less time spent in the South Atlantic Anomaly (SAA).

  17. Definitions • Level 0 Processing - Space-to-ground artifact removal • Processing of raw instrument data. Level 0 data processing consists of time-ordering packets, removing corrupted, incomplete, or duplicate packets, annotating quality, and can include separating housekeeping, calibration, science, and engineering data streams. • Level 1 Processing • Processing level 0 data into level 1 data consists of creating a database of reconstructed gamma-ray photons and cosmic rays which includes energy, direction of arrival, arrival time, quality parameters, and associated pointing and livetime history. • Higher Level Science Processing • Processing of level 1 data into science products. Consists of calculating exposures, detecting sources, measuring their spectra, determining their time histories, and locating potential counterparts in other astronomical catalogs .

  18. LAT Data Path Realtime data: 32 kbps S-band SSR dump: 15 Mbps X-band Prime - 2 MbpsIntelsat ASINet Central Node Fucino, Italy JSC Houston 32 Mbps Backup - 500 kbps Malindi Realtime S-Band Data and SSR Data Malindi gets ~35 Gbits per day from GLAST and 26 Gbits From Swift, and AGILE Equivalent to ~400 kbps continuous NISN or ASINet NISN or Internet 2 via JPL MOC (TBD) LAT IOC Stanford NISN or Internet 2 via ARC NISN should support whatever rates we deem necessary for the desired latency Another option is Internet 2 Realtime S/C and LAT HSK Data Followed by processed Level 0 Data

  19. The LOF will consist of about 1/2 the resource of the FUSE Control Center at Johns Hopkins University (as shown here). LAT Operations Facility Functions LAT Instrument Operations & Science Data Processing Data Processing Facility WBS 4.1.D LAT Operations Facility WBS 4.1.B Level 0 Science & Hsk Data S. Williams, SU-HEPL R. Dubois, SU-SLAC • LAT Data Verification • LAT Health & Safety Monitoring • LAT Commanding • Test & Calibration Data Acquisition • Validating & Maintaining Flight Software • Alert Processing • Science Data Processing • Optimizing Analysis & Processing Algorithms • LAT Calibration • LAT Performance Assessment • Data Distribution • Analysis Software • Mirror Sites Performance & Cal Data Science Plan, LAT Schedules Level 0 Data, LAT Procs & Uploads Science Support Center (SSC) Level 1 Data, High Level Products, LAT IOC Data Products Mission Operations Center (MOC) Science Plan, Schedules, Level 0 Data Level 1 Data, High Level Products, GBM IOC Data Products, GBM Schedules, Science Plan S/C LAT, and GBM Data, Commands GBM Instrument Operations Center Space and Ground Segments Level 0 Data, GBM Procs & Uploads

  20. GLAST Mission Operations Center GBM Data Sets GBM IOC Alerts, Telemetry SPACE NETWORK Real-time telemetry Commands, TOO, Loads Mission Operations Center Selected Playback Tlm Schedules Commands, Loads Status As flown timelines Orbit Data GBM Alerts • Mission Scheduling • Commanding • Observatory safety • Spacecraft health • Orbit Prediction • Alert message routing • GBM Data Handling • Data Distribution • Instrument Health LAT Data Sets Real-time Telemetry LAT IOC GROUND STATION NETWORK Real-time telemetry GBM, Playback,S/C tlm Selected Playback Tlm Commands, Loads Commands, Loads Schedules As flown timelines Status LAT Alerts Acquisition Data GRB COORDINATES NETWORK SSC Schedules S/C data for archiving As flown timelines Burst/Transient Alerts TOO

  21. References • GSFC 433-SRD-0001, GLAST Science Requirements Document, P. Michelson and N. Gehrels, eds., September 23, 2000. • GSFC 433-OPS-0001, GLAST Operations Concept Document, Baseline, March 8, 2002. • GSFC 433-PLAN-0009, GLAST Project Data Management Plan, DRAFT, December 2001. • GSFC 433-SPEC-0001, GLAST Project Mission System Specification, April 24, 2001. • GSFC 433-IRD-0001, GLAST Science Instrument - Spacecraft Interface Requirements Document, January 23, 2001. • LAT-TD-00428-03, LAT Instrument Operations Center Preliminary Design Report, January 31, 2002. • LAT-TD-00447, GLAST LAT Calibration Plan, December 5, 2001. • LAT-TD-00446, GLAST LAT Calibration Requirements, December 5, 2001. • LAT-TD-00499, LAT Operating Modes, 30 May 2001. • LAT-TD-00501, LAT Mission Phases, 12 December 2001. • LAT-SP-00015, LAT Instrument Operations Center - Level II Specification, Sept. 1, 2000. • LAT-SS-00021-07, LAT Operations Facility Subsystem Specification-Level III Specification, January 7, 2002.

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