Transcript Slides (includes agenda)

GLAST LAT Project
ISOC
LAT Operations Scenario
Subsystem Meetings
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ISOC
GLAST LAT Project
Agenda
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Define LAT operation phases
Overview of LAT commanding
Describe subsystem operations
Identify potential contingencies and actions
Identify MOC monitoring and activities
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ISOC
GLAST LAT Project
LAT Operations Phases
• I&T
– Pre-FSW
– Post-FSW
• L&EO
– LAT turn-on
– Initial checkout
• First year
– Survey mode
• Second and subsequent years
– Pointed observation
– Survey mode
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GLAST LAT Project
ISOC
LAT Commanding during On-orbit Operations
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ISOC identifies one or more command mnemonics and any
associated parameters and upload files to accomplish the desired
function
– Command and files are validated on testbed
Command mnemonics and files are transmitted to GLAST Science
Support Center (GSSC)
– Integrate guest investigator requests and instrument commands
into observatory timeline
– Send command information to MOC
MOC schedules TDRS link for commanding (or use a pass routinely
scheduled for SSR dump)
– MOC uses ITOS and LAT database to create LAT commands from
the command mnemonics
– Commands are loaded into an Absolute Time Sequence (ATS) that
is transmitted to spacecraft
• Spacecraft sends ATS commands to LAT at the assigned times
– Files are uploaded in real time and may be committed at that time
or later via an ATS command
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ISOC
GLAST LAT Project
How the ISOC Commands the LAT
LAT db
LAT
C&T db
This is the same
LAT C&T db
Project db
ISOC decides what
they want to do
Example: Select an onboard configuration
table
ISOC uses ground software to
determine the correct CCSDS-format
command to accomplish the desired
function and then convert to the
correct command mnemonic
or determine the correct command
mnemonic directly
...101101101010111010001010100...
mnemonic
LCONFIGTBLSEL table=XYZ
ISOC sends only the mnemonic and
parameters to the GSSC along with
info on what it is, when to send it,
criticality, etc. *
LCONFIGTBLSEL table=XYZ
GSSC incorporates the command
into the observatory timeline and
sends it to the MOC
LCONFIGTBLSEL table=XYZ
LAT
C&T db
MOC uses ITOS and the database to translate the
command mnemonic and parameters back into
the CCSDS format and adds the necessary suffix
and prefix for transmission to the spacecraft
...111000...101101101010111010001010100...0101110...
*In the case of a file upload, the binary data file is formatted for ITOS at the ISOC
using a Perl script (make_load_file_) and the file is sent to GSSC
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ISOC
GLAST LAT Project
Subsystem Operations
• What subsystem-related commanding occurs during:
– Initial checkout
– Survey mode
– Pointed observation
• Scope of commanding
– How many commands per day, week or month?
– Size of files
– Real-time or ATS
• Are there any special requirements?
– Pointing dependency (attitude dependency impacts TDRS
scheduling)
– Criticality of commanding
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ISOC
GLAST LAT Project
Contingency Plans
• What are some possible anomalous conditions?
• Symptoms of a problem
– What data is being monitored by LAT?
– What data is being monitored by spacecraft?
– What needs to be monitored by MOC/ISOC?
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ISOC
GLAST LAT Project
MOC Responsibilities
• What housekeeping data would MOC look at?
• What diagnostic data would be meaningful for MOC?
• What response does MOC take for alert data?
– Notify ISOC and perform contingency procedure
– Notification only
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