Description and Benefits of JWST Commanding
Operations Concept
TIPS/JIM Meeting
17 July 2003
Vicki Balzano
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Description and Benefits of JWST Commanding
Operations Concept
Three main components of JWST Commanding
Operations Concept:
– Event-Driven
– High-Level Ground-to-Flight Interface
– Human-Readable Uplink Format
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Description and Benefits of JWST Commanding
Operations Concept
• What is Event-Driven Operations?
– The ability to react to on-board events without ground
interaction
• For HST:
[Primarily absolute time based]
» Flight Software monitors health and safety
» SI Operational Software has limited ability to
react through use of “event flags”
• For futuristic “robot” mission:
» Flight Software monitors health and safety
» Operational Software given proposal information and
does ALL the scheduling
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Description and Benefits of JWST Commanding
Operations Concept
• What is Event-Driven Operations?
• For JWST:
» Flight Software monitors health and safety
» Ground Software does visit ordering and constraint
specification (for example: time windows)
» Flight Software initiates each visit in the list as its
constraints are met and after previous visit completes
» Operational Software has access to all telemetry so…
next operation occurs immediately after the previous
operation completes and execution strategy can be
based upon on-orbit events.
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Description and Benefits of JWST Commanding
Operations Concept
• JWST Commanding Architecture
• Ground Software creates Visit Files
» An ordered list of ASCII high level statements
Similar to SMS statements but at “higher” level
and NO absolute time stamps
» Assigned a time window (earliest start, latest start,
latest end)
Visit statement example:
Activity, 07, MIRIMAGE, filter=F15W, sample=STEP24, exptime=1000 ;
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Description and Benefits of JWST Commanding
Operations Concept
• JWST Commanding Architecture
• Ground Software creates Observation Plan
» An ordered ASCII list of visit files
• Ground System uplinks Observation Plan and
associated Visit Files once a week
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Science Operations
- Observation Plan Graphic Visit 00301
E
e
l
f
Successful completion
Visit 05505
E
e
l
f
Successful completion
Visit 09008
e
e = earliest start time
l
l = latest start time
f
f = latest end time
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Science Operations
- Observation Plan Graphic Visit 00301
x
e
l
f
Guide star acq failure
Visit 05505
E
e
l
f
Successful completion
Visit 09008
e
e = earliest start time
l
l = latest start time
f
f = latest end time
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Description and Benefits of JWST Commanding
Operations Concept
• JWST Commanding Architecture
• Flight Software processes Observation Plan and
Visit Files
» Known as the OPE (Observation Plan Executive)
» Reads ASCII input, checks constraints, coordinates
parallel operations, manages interruptions
» When error is encountered, can skip items but
CANNOT reorder plan.
» Calls on-board operational software to execute visit
file activity statements
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Description and Benefits of JWST Commanding
Operations Concept
• JWST Commanding Architecture
• On-board Operational Software
– In the form of ASCII JavaScript programs
– Similar to HST instructions but in robust software
language
» Each script contains operational rules and flight
software application requests necessary to accomplish
a high-level task (ex. Guide star acquisition,
NIRCAM exposure, MIRI alignment, wave-front
sensing)
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Description and Benefits of JWST Commanding
Operations Concept
Benefits of JWST Event-Driven Operations
Takes advantage of L2 orbit, the hardware architecture, the absence
of many time-critical operational constraints and the capabilities
of modern flight computers
• Minimal task modeling in ground software
– Decreases size and complexity of ground software system
• Execution efficiency
• Minimizes down-time due to instrument safings
• Enables rapid workarounds to unexpected spacecraft
behavior
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Description and Benefits of JWST Commanding
Operations Concept
Benefits of JWST High-Level Ground-to-Flight Interface
• Guarantees common scripts for both real-time and
planned operations
• Minimizes transition from I&T to Operations
• Decreases response-time to spacecraft and
instrument anomalies because programming in a
high-level scripting language
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Description and Benefits of JWST Commanding
Operations Concept
Benefits of JWST Human-readable Uplink Format
• No bit-busting (binary command load verification)
• ASCII format corresponds to descriptions in usermanuals and user proposal forms
• It is human friendly: lowers risk of interpretation
errors
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