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GLAST Large Area Telescope ISOC Use of LAT Diagnostic APIDs 8 March 2005 Rob Cameron

Gamma-ray Large Area Space Telescope. GLAST Large Area Telescope ISOC Use of LAT Diagnostic APIDs 8 March 2005 Rob Cameron rac@slac.stanford.edu 650-926-2989. Agenda. Background: Summarize Alert APID and Diagnostic APID potential conflict

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GLAST Large Area Telescope ISOC Use of LAT Diagnostic APIDs 8 March 2005 Rob Cameron

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  1. Gamma-ray Large Area Space Telescope GLAST Large Area Telescope ISOC Use of LAT Diagnostic APIDs 8 March 2005 Rob Cameron rac@slac.stanford.edu 650-926-2989

  2. Agenda • Background: Summarize Alert APID and Diagnostic APID potential conflict • Review current LAT diagnostic APID telemetry usage • Unsolicited, solicited, dwell • Determine operational constraints to avoid alert/diag conflicts • Assess impact of operational constraints

  3. Background • Diagnostic Telemetry has the following uses: • Its use would be limited to specific activities where additional data is required • Component checkouts: Calibration data • Trouble shooting: Table dumps, Memory dumps • Its use would be limited to specific times • Scheduled downlinks, lasts for the duration of a contact or several contacts • Command driven (MOC, ATS or RTS initiated) • Event Driven (Fault detection) • Because of these (agreements from 11/02), Diagnostic telemetry is assigned same priority (queue) as alert telemetry • Only difference is the ‘Alert’ APID range initiates a link.

  4. Background (cont.) • TDRSS MA link • 1 kbps downlink for shared Alert and Diagnostic telem • Presence of Diagnostic telem can impact Alert data • Resulting potential problems from continuous Diag data • Potential delay of alert data – science impact possible • Presence of diagnostic data will prevent alert-initiated link from closing – thermal / power impact possible • Link closes after 180 seconds with NO data in the alert/diag queue • SSR Partition sizing (very minor issue)

  5. LAT Diagnostic APID Usage • Unsolicited • Command Response • can be turned on, off, or restricted to response only on error • EPU boot • rare, but (currently) unlimited duration, until stopped by ground cmd • NOTE: EPU boot data stream might be put in HSK • TCS status • 1700 bits/packet • can be turned on/off • can be throttled: 0.1 Hz max packet rate? • NOTE: most important TCS status will be put in HSK • Solicited • MSG system: contents TBD • MEM: SIU, EPU mem dump, OS and App pool space, symbols • LFS: directory and file listings, FS status, file dump • LIM: Instrument manager: contents TBD • Dwell • Solicited • Commanded number of samples • Higher cadence HSK

  6. Resolving Any Conflict • Potential solutions • SC changes: lower diagnostic priority, diagnostic telemetry doesn’t keep alert link open ($$$) • LAT changes: change “routinely if enabled” and “unsolicited” Diagnostic packets as packets sent across the science data or HSK channels • Operational: ISOC keeps all or subset of “routinely if enabled” features disabled or at low rate during science collection

  7. Operational Constraints • TCS • NOTE: Cannot keep TCS diag on, as the Alert-initiated MA link would never close • EPU Boot • rare • NOTE: continuous diag data stream is a concern unless moved to HSK, but assess impact of extra 3.2 kbps in HSK • MEM • used infrequently? • use only during RT for monitoring? (But not a concern for pool space: small dataset) • LFS • File System Status: monitor at least daily, during RT (but only a small response) • Directory or Root Listing: used infrequently, only during RT? • File Dump: use only during RT, and/or use via science stream • MSG, LIM • TBD impact • NOTE: ISOC should plan to dump and clear MSG log at least daily, during RT • ITC, command response • Response should be on for all ATS commands • low rate, limited response – acceptable impact • Response can also be on for file uploads during RT • Dwell • Constraint on ISOC usage, to be assessed case by case • Duration should be limited as much as possible • NOTE: Should ISOC use diag commanding in ATS, to coincide with planned RT schedule? • Potential impact on Alert capability if scheduled RT comm is missed

  8. Considerations from Erik Andrews • EPU ‘Reboot’ a special case with special considerations • EPU providing 3.7 kbps of telemetry (is this true?) • If SA link is ‘on’, then rate is 1, 2, or 4 kbps. (This would be a concern). • If MA link is ‘on’, then 1 kbps will be the rate. • Reasonable to buffer/store this data on the SIU? • Command Response – Does a command log exist? Could one be maintained and then dumped periodically. Would contain cmds and disposition/status. • Errors – Does an error log exist? Would likely include a flag in a tlm packet header somewhere to indicate errors existed (or log empty/not empty) • TCS, LSW – since not yet built, maybe can use alternative to ‘unsolicited’? • Testing thoughts - • What telemetry (of any kind) does FSW need for its FSW testing to verify requirements? • What telemetry (of any kind) does DAQ need for its testing of the subsystem to verify requirements? • What telemetry (of any kind) does LAT I&T need for its verification and testing of instrument requirements? • What telemetry (of any kind) does LAT I&T / ISOC need for Observatory I&T (or on-orbit) testing and checkout?

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