1 Description and Benefits of JWST Commanding Operations Concept TIPS/JIM Meeting 17 July 2003 Vicki Balzano

2 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

3 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

4 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.

5 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 ;

6 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

7 Science Operations - Observation Plan Graphic - elf Visit e = earliest start timel = latest start timef = latest end time elf Visit elf Visit E Successful completion E

8 Science Operations - Observation Plan Graphic - elf Visit e = earliest start timel = latest start timef = latest end time elf Visit elf Visit x Guide star acq failure Successful completion E

9 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

10 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)

11 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

12 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

13 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 user- manuals and user proposal forms It is human friendly: lowers risk of interpretation errors