HST Scheduling System Two-Gyro Science_ Phase I Operations Concept

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					   HST Scheduling System
  Two-Gyro Science, Phase I
    Operations Concept and
Functional Requirements Review

         October 24, 2003
                                     Agenda (1 of 2)
            Introduction                   C. Myers        9:00 – 9:10
                 Background
                 Overview
            Operational scenarios          M. Reinhart     9:10 – 9:35
                 TGS modes and scenarios
                 Science impact studies
            Long-range planning (SPIKE)    M. Giuliano     9:35 – 10:00
                 Prototype work
                 Requirements summary
            Short-term scheduling (SPSS)   S. Stallcup,   10:00 – 10:45
                 Requirements summary      S. Speck
                 Design concept

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                                    Agenda (2 of 2)
            Short-term scheduling (PASS)                   10:45 – 11:30
                 Requirements summary      C. Darby
                 Design concept            R. McCutcheon
            Commanding / PRD                               11:30 – 11:45
                 Command impacts           A. Welty
                 PRD impacts               M. Bielefeld
            Testing planning               L. Foor         11:45 – 11:55
            Interfaces                     R. McCutcheon   11:55 – 12:10
            Summary                        C. Myers        12:10 – 12:30
                 Risks / issues
                 Schedule

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              Carey Myers

10/24/2003                  4
                       Purpose of Review

        Ensure that we have a feasible operations concept
        Ensure that we have a complete set of Phase I
         functional requirements that will enable implementation
         of a basic two-gyro science (TGS) capability
        Define an initial design concept that can provide the
         basis for a full end-to-end TGS mode of operations

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                             Problem Statement
            The HST Project has tasked us with developing a TGS mode
            The TGS mode is a means to provide spacecraft attitude control
             and slew capability, in the condition of only two remaining
             operational gyros, with sufficient accuracy to continue science
             gathering operations
            It is a contingency mode primarily targeted for use in the event
             the HST is in a two-gyro condition before SM4
            It is also considered a degraded mode in that science operations
             will be capable of being performed, but with less efficiency and
             flexibility compared to normal operations with three gyros
            Particular classes of science observations likely will be heavily
             constrained or not possible
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             HST Scheduling Process

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                   HST Scheduling Systems
       Astronomer’s Proposal Tools (APT): Suite of tools enabling
        astronomers to design and submit detailed proposed science
        observations (visits)
       Transformation (TRANS): System that translates each proposed
        visit into a detailed plan for execution
       Science Planning Interactive Knowledge Environment (SPIKE):
        System that creates and manages the HST long-range science
       Science Planning and Scheduling System / Science Commanding
        System (SPSS / SCS): System that creates the weekly calendar
        and generates the science mission specification (SMS)
        POCC Applications Software Support (PASS): System that
         processes the SMS and generates the binary command loads for
10/24/2003                                                              8
         uplink to HST
                      Phased Implementation Approach
        The scheduling system two-gyro science support
         will be a two-phased implementation
                Phase I will support TGS in the continuous viewing zone
                 (CVZ) with limited support for full-sky science
                     Requires reworked science visits and manual scheduling
                     Impacts primarily SPSS and PASS: Enhancements to existing
                      scheduling algorithms as opposed to major function replacement
                Phase II will incorporate enhancements to support
                 automated TGS proposal submission and long-range
                     Will incorporate lessons learned from Phase I
                     Impacts primarily APT, TRANS, and SPIKE: Additional PI tools
                      and incorporation of scheduling constraints

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             TGS Implementation Team

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             Documentation Status

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             Operational Scenarios

                 Merle Reinhart

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                    TGS Modes and Scenarios:
        Currently, operations uses three gyros to provide rate control at
         all times; attitude errors are limited to nominally a couple of
         hundred arc-seconds worst case after very large vehicle slews
        Onboard attitude updates using FHST data are done to get errors
         within FGS search radius
        FGS data are used with gyro data to hold spacecraft position
         during science
        With only two gyros and MSS data, we may start with degrees of
         attitude error each orbit
        FHST and / or FGS data are needed to control the rates as well as
         correct the attitude

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                           TGS Modes and Scenarios:
        Two active gyros are available; these measure the vehicle rates in the
         plane formed by the input axes of the two gyros
        Another sensor is required to estimate the vehicle rates normal to the
         two-gyro (input-axes) plane
                MSS
                      Measures magnetic field vector
                      Always available
                FHSTs
                      Measure star vector
                      Provide accuracy required to start using the FGSs
                FGSs
                      Measure the guide star vector
                      Provide accuracy required for science
                Rate of change of the measured vector is used to estimate vehicle rates
                 normal to the two-gyro (input-axes) plane
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             TGS Scenario

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                         Two-Gyro Mode: Overview
       TGS modes are based on an alternate sensor being used in place
        of a third gyro
             MSS / two-gyro (M2G) mode: Normal entry only from FHST / two-gyro mode
             FHST / two-gyro (T2G) mode: Default entry from safemode
             FGS / two-gyro (F2G) mode: Entry only from FHST / two-gyro mode
                                                                                           Safe Mode

                                 M2G Mode
                   Mode                                                                     T2G Mode
                 Transition    Rate Estimation
                               based on 2 gyros                                           Rate Estimation
             Rate Estimation    + MSS and on-                                             based on 2 gyros
                 Failure       board Mag field                                                + FHST
               Transitions          model
                 from                                      F2G Mode
                                                    Rate Estimation based on 2
                                                  gyros + FGS data (in FL or CT)
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                                  Two-Gyro Mode: M2G

            Modes defined in M2G
                Attitude hold: Only path for normal transition to and from T2G
                Maneuver: Large vehicle (type 2) slews

                       Mode            M2G Mode
                   Ops Mode
                 Rate Estimation
                     Failure                        Maneuver

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                              Two-Gyro Mode: T2G
      Modes defined in T2G
            Attitude hold / rate capture: Only path for              Maneuver / attitude correction
                Normal transition to and from M2G                    Guide star acquisition
                Normal transition from F2G                              Only path for transition to F2G

            Attitude determination (OBAD)                               Spans T2G and F2G

                                                                 T2G Mode
               Mode                                        Attitude Determination

             Ops Mode
                                                                 Maneuver / Att. Correction
         Rate Estimation
             Failure                                       Attitude Hold /
           Transitions                                      Rate Capture
               from                                             Guide Star Acquisition               Safe Mode
             Safemode                                                                              (ZGSP/PSEA)
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                                   Two-Gyro Mode: F2G
            Modes defined in F2G
                Guide star acquisition
                      Spans T2G and F2G
                      Only entry path for F2G
                Maneuver / science slew
                      Decenterline slew, error correction
                      Profile slews, peakups, scans etc.
                Science
                      Fine guidance
                                                                       F2G Mode
                                                                        Guide Star Acquisition
                   Ops Mode
                   Transition            T2G                 Science
                 Rate Estimation
                     Failure                                                         Maneuver
                   Transitions                                                     (Science Slews)

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               What We Lose in Two-Gyro Mode

        Smallest aperture, highest spatial resolution science programs
         are likely to be infeasible
        No pointed gyro science observations (Earth calibrations may
         be an exception to this)
        No handoffs from guide star control to gyro control
        No guide star handoffs
        No single FGS guiding
        No target acquisition information carried over from orbit to
         orbit (i.e., must repeat the target acquisition in each orbit)
        No moving target observations (at least in Phase I)

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                 FHST Star Density Study (1 of 2)
       For the OBADWG, a star density study was conducted to
        determine if sufficient stars will be available for
            FHST rate control
            FHST onboard mapping, star identification, and attitude correction

10/24/2003                                                                        21
                   FHST Star Density Study (2 of 2)
       Star count analysis indicates that
            The chance of not finding a rate control star in one of the three FHSTs is
             exceedingly small
            Away from the galactic plane, there are regions where there are fewer than
             three stars available for a given tracker
                 Thus there is a small chance that the FHST used as a mapping tracker will
                  have fewer than three stars
                 Due to the different orientations of the three FHSTs, it is unlikely that all three
                  trackers will see fewer than three stars at a given time

       Conclusions
            FSW requires logic to switch between rate control and mapping trackers if
             the mapping tracker finds insufficient stars
            The planning systems should retain an optional capability to specify the
             mapping FHST based on star density expectations for the three FHSTs
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                 Science Impact Studies

              CVZ scheduling study
              All-sky target availability study
              Current cycle scheduling study

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                              CVZ Scheduling Study
        Status: Nearly complete; need to complete analysis of the effect of
         changing the timings and to write up the final results
        Built upon earlier work done to evaluate the potential of using the
         CVZ as a way of achieving relatively high observing efficiency
        Evaluated using the north and south CVZs for early operations
                Evaluated the ability to cover SAA passages with FHST availability
                Estimated how many orbits are schedulable and how many will be lost due to
                 uncovered SAA passages
                      Number of usable orbits varies from ~7 to 15 orbits per day
                      A scheduling efficiency >~ 50% is implied
                Evaluated the level of scheduling flexibility available (via off-nominal roll,
                 etc.) to adjust these uncovered periods
        Results of study can be used to evaluate potential early two-gyro
         science programs
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             Northern FGS CVZ -Nominal Roll

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             Southern FGS CVZ -Nominal Roll

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                     All-Sky Target Availability Study
        Status: In progress; proposals / targets to be used have been written;
         expect to be completed by the end of the year
        Assess the availability of targets across the entire sky
                Driven by FHST scheduling restrictions
                Provide basic information about when and how various portions of the sky
                 are accessible
                Instantaneously, expect <50% of the sky to be available (predominantly due
                 to FGS / FHST visibility synchronization)
        Perform schedulability sensitivity studies
                Vary worst case pointing error in M2G / T2G
                Vary FHST durations and timings for transitions from T2G to F2G
        Utilize SPIKE and other tools to evaluate a grid of targets over the
         entire sky, comparing the results to nominal operations
        Provides insight into how much of any pre-existing observational
         program could be supported
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                     FGS vs. FHST Visibility (1 of 2)

            Example of visibilities that are unusable with two-gyro science ops
            In this case, the target is east of the Sun

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                     FGS vs. FHST Visibility (2 of 2)

            Example of visibilities that support two-gyro science ops
            In this case, the target is west of the Sun

10/24/2003                                                               29
                     Current Cycle Scheduling Study
        Status: Start early next year
        Evaluate what fraction of an entire cycle could be scheduled using
         a representative pool of observations
        Results will help determine the observing policies that the STScI
         would put in place to support two-gyro mode
                If only a few typical cycle observations can be scheduled as originally
                 requested, then it is likely that development of a new observing program
                 would be necessary ASAP (while carrying out an interim CVZ campaign)
                If a substantial fraction can be scheduled in two-gyro mode, then more
                 time to respond will be available, and potentially a new program could
                 simply be brought in with the next planned observing cycle
        Details are to be defined as previous studies are completed

10/24/2003                                                                                  30
             Long-Range Planning: SPIKE

                     Mark Giuliano

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             HST Scheduling Systems

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                                   SPIKE Background
      Science Planning Interactive Knowledge Environment (SPIKE) is a
       highly adaptable constraint-based software system for planning and
       scheduling astronomical observations
      SPIKE works in terms of constraint windows and plan windows
            Constraint windows: Intervals in which an observation can satisfy all its
             physical (e.g., Sun / Moon avoidance) and observer-specified (e.g., ob1 after
             ob2 by 10-20 days) constraints
            Plan windows
                 Subset of constraint windows (nominally 8 weeks)
                 Selected via heuristic search to optimize resource usage and user-tunable criteria
                 Used by SPSS to create a pool of candidate SUs for building an SMS

      SPIKE is run under various guises by various HST user communities
            Observers run SPIKE through APT to determine and analyze visit schedulability
            STScI staff use SPIKE to build and maintain the HST Long-Range Plan (LRP)

10/24/2003                                                                                             33
                        TRANS Background

       Transformation (TRANS) is a knowledge-based software
        system that takes proposal observation descriptions and
        generates a detailed plan for executing the observations on HST
       TRANS creates support activities (e.g., buffer dumps), models
        instrument overheads (e.g., filter moves), and groups activities
        into a hierarchy based on exposure pointing and engineering
       A TRANS observations plan is used by observers to pack orbits
        (as part of APT) and by downstream systems for planning,
        scheduling, and data analysis

10/24/2003                                                                 34
                         SPIKE Prototyping Efforts

            Since July 2003 the SPIKE team has been developing
             prototype two-gyro scheduling capabilities
                The purpose of this effort is to provide tools that can be
                 used to characterize and analyze the impact of two-gyro
                 constraints on HST scheduling
                     The tools will support the science impact studies described
                The prototype will also form the basis of the final
                 implementation of SPIKE two-gyro support

10/24/2003                                                                          35
                   SPIKE TGS Design Concept
       Divide the implementation of two-gyro constraints into two
            Model the required FHST overlaps
                 The exact requirements for the overlaps are expected to be volatile
            Integrate an FHST visibility constraint into SPIKE
                 Integration with existing GUI, constraint infrastructure, and roll angle code
                 Nonvolatile

       Determine how much (if any) of an orbit is available for
        FHST scheduling by incorporating the FHST overlap model
        into the FHST visibility constraint
            Feed the resulting orbit structure into the existing SPIKE orbital
             viewing constraint (code reuse)
            Sample FHST visibility over legal roll ranges for a day
10/24/2003                                                                                        36
                     Schedulable FHST Overlaps





    FHST 3

    FHST 2

    FHST 1



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              Unschedulable FHST Overlaps







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             SPIKE GUI Snapshot

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                  SPIKE TGS Requirements Summary

            SPIKE will provide two-gyro scheduling constraints
             for APT proposal processing and long-range planning
                SPIKE will model FHST visibilities
                SPIKE will implement two-gyro constraints based on FHST
                SPIKE will integrate two-gyro constraints with existing
                 constraint infrastructure and visualization tools
                SPIKE will model FHST / SAA impacts
                SPIKE will integrate FHST roll restrictions with existing
                 roll constraints

10/24/2003                                                                   40
                 SPIKE Study Support Status (1 of 2)

       FHST visibility study support – Completed
            SPIKE already modeled FHST visibility
            Verified correctness of the model
       All-sky target availability study support - Completed
            Working on configuration and delivery issues
            Added FHST overlap constraints to SPIKE
            Integrated with SPIKE constraint and visualization tools
            Integrated with orientation restrictions

10/24/2003                                                              41
                      SPIKE Study Support Status (2 of 2)

        Current cycle scheduling study support (Nov. 2003 -
         Jan. 2004)
                Complete SAA modeling
                Perform TRANS preparation work to account for less
                 visibility time due to extended PCS acquisition times
                Requires no TRANS code changes
                     Model times via input parameters
                     Use existing TRANS orbit fill capability to shrink orbits
                     Rebuild TRANS with new visibility model table

10/24/2003                                                                        42
        Short-Term Scheduling: SPSS / SCS

                   Scott Stallcup
                    Scott Speck

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             HST Scheduling Systems

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                      SPSS Background (1 of 2)
                Science Planning and Scheduling System (SPSS)
                    Short-term scheduler for HST science observations
                    Schedules activities to the nearest second
                    Scheduling constraints include
                         Bright / dark Earth avoidance
                         Sun / Moon avoidance
                         SAA avoidance
                         Target visibility (input from MOSS)
                         Power constraints
                         Thermal constraints
                         SI state restrictions
                         Guide star constraints (input from NGSS)
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                      SPSS Background (2 of 2)
            Scheduled activities include
                 Slews
                 Small-angle maneuvers
                 Track 51 scans
                 PCS acquisitions / reacquisitions
                 Guide star handoffs
                 Target acquisitions
                 FHST updates
                 Science instrument reconfigurations
                 Science activities
                 Calibrations
                 Recorder activities
            Written in F77, C++, and Java in 520,000 lines, 54 applications
10/24/2003                                                                     46
                            SCS Background

            Science Commanding System (SCS)
                Takes “calendar” of observations from SPSS and
                 produces a science mission specification (SMS) for
                 input to PASS by interpreting command instructions
                Generates high-level HST commands from the SPSS
                 “calendar” of science and other activities
                Written in F77, C++, and Java in 220,000 lines,
                 19 applications

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                  Proposal Management Data Base

       Proposal Management Data Base (PMDB)
            Relational data base that contains all observation proposal data
            Observation structure
                 Proposal
                 Scheduling unit (visit)
                 Observation set
                 Alignment
                 Exposure
            Also contains ephemeris data, linkset data, and other items

10/24/2003                                                                      48
                    SSPS Calendar and Candidate List

            Calendar and Candidate (C&C) List
                File and data structure
                Contains a candidate pool of observations from the PMDB
                Contains a calendar of scheduled observations for a given
                 time period
                Generally covers 1 week of observations
                SPSS scheduling commands work only with C&C list files,
                 not the PMDB

10/24/2003                                                                   49
                      SPSS Scheduling Concept (1 of 2)

        SPSS scheduling begins with an empty calendar and a
         pool of candidate observations (scheduling units - SUs)
         to be scheduled
        Candidate SUs may be scheduled automatically as a
         group or individually using SPSS commands
        Scheduling is attempted for a particular time span
                If the candidate can be scheduled within constraints, it will be,
                 and the scheduled efficiency will be reported
                If the candidate cannot be scheduled, the reasons for the failure
                 are reported

10/24/2003                                                                           50
                   SPSS Scheduling Concept (2 of 2)

            As the software adds activities within an SU, it checks all
             constraints and, if required, delays activities until the
             constraints are clear; it continues this process with all
             necessary activities until all activities are scheduled or the
             end time is reached
            SPSS does not schedule SU activities in time order from
             beginning to end; the scheduling order for each alignment is
                Science activities
                PCS activities
                SI activities
                Slews
                FHST updates

10/24/2003                                                                    51
                  SPSS TGS Requirements Summary:
                      Data Base and C&C List

            SPSS will query the PMDB for all parameters for two-gyro
             operation and store these data in the C&C list
            SPSS will designate a new C&C list as either two-gyro or
             non-two-gyro; only two-gyro observations will be added to a
             two-gyro C&C list and vice versa for a non-two-gyro C&C
            SPSS will issue errors when a moving-target observation is
             set to use a two-gyro PCS scenario

10/24/2003                                                                 52
                   SPSS TGS Requirements Summary:
                         Scheduling (1 of 3)
            In two-gyro mode, gyro scheduling units will be scheduled only
             in M2G mode
            When scheduling an alignment, SPSS will first determine
             whether the HST is in M2G or T2G mode
            For the HST to be in T2G mode, FHST windows must exist from
             the previous FGS loss-of-usability through the resumption of
             F2G mode; SPSS will calculate these windows using a small
             attitude uncertainty
            In M2G mode, FHST windows will be calculated using a large
             attitude uncertainty, from the end of the previous slew to the start
             of F2G mode
10/24/2003                                                                          53
                SPSS TGS Requirements Summary:
                      Scheduling (2 of 3)
        To transition the HST from M2G to T2G mode, an initial FHST
         rate control activity will be scheduled
        SPSS will schedule initial FHST map and attitude correction
         activities at the earliest time when two FHSTs are visible for the
         required duration
        SPSS will calculate FHST windows using a medium attitude
         uncertainty after the first attitude correction to determine the next
         place where two FHSTs are visible for a second map and attitude
        SPSS will schedule a second FHST map and attitude correction,
         ending as close as possible to the start of the FGS PCS acquisition
10/24/2003                                                                       54
               SPSS TGS Requirements Summary:
                     Scheduling (3 of 3)
        SPSS will calculate FHST windows using a small attitude
         uncertainty to determine when one FHST is visible until F2G mode
         is achieved
        SPSS will schedule an FHST observer mode activity that ends
         partway through the FGS PCS acquisition, when F2G mode is
         established; no FHST handoffs will be permitted during this
         observer mode activity
        When more targeted alignments need to be scheduled after FGS
         loss-of-usability, a full FGS acquisition will be scheduled if the
         HST is in T2G mode; otherwise, a full set of FHST maps and
         attitude corrections will be scheduled before the FGS acquisition

10/24/2003                                                                    55
                  SPSS TGS Requirements Summary:

            SPSS will display the new FHST activity types on a
             calendar, as well as the FHST visibility windows on a
             calendar using any of the HST pointing uncertainties
             associated with two-gyro scheduling

10/24/2003                                                           56
                  SPSS TGS Requirements Summary:
                         SMS Generation
            The SMS generation (SMSG) process will
             recognize the new FHST activity types
                FHST tracker identification will be provided via SCPL
                 pseudo-instruction if set by SPSS scheduling for FHST
                 or guide star acquisition activities
                FHST mode information will be available via SCPL
                Where practicable existing pseudo-instructions will be
                 enhanced to provide this additional information

10/24/2003                                                                57
                 SPSS / SCS TGS Design Concept
                            (1 of 3)
       SPSS will operate in two general modes: two-gyro and three-gyro
        modes controlled by a flag in the PMDB
       Users will be able to create C&C lists and SMSs in either mode,
        depending on the state of the flag
       There will be no user interface changes required for SPSS / SCS,
        though the displayed items with the display tools will change slightly
       In three-gyro mode, SPSS schedules FGS acquisitions and
        reacquisitions; in two-gyro mode, it schedules only acquisitions
       No FGS specific code changes will be required because FGS
        operations in SPSS are table driven based on named guiding
        scenarios, although overlapping FHST visibility will be needed
        through the first part of FGS activities
10/24/2003                                                                       58
                     SPSS / SCS TGS Design Concept
                                (2 of 3)

        Most of the software changes will be isolated to the FHST
         processing components in SPSS
                In three-gyro mode, FHST updates will be scheduled as they are today
                In two-gyro mode, FHST updates will not be scheduled; instead, onboard
                 maps and attitude corrections will be scheduled
        Currently, FHST visibility windows are computed with a constant
         HST pointing uncertainty; under two-gyro mode, three separate
         FHST visibility window calculations will be needed
                Different pointing uncertainties will be associated with the first and
                 second map / attitude correction activities and the FHST / FGS observer
                 mode activity

10/24/2003                                                                                 59
                SPSS / SCS TGS Design Concept
                           (3 of 3)

        The most significant change to the scheduling algorithm involves
         the need to schedule FHST maps, attitude corrections, and FGS
         activities with one or two FHSTs simultaneously visible as
        Existing event display tools (“calendar display” and “sgs”) will be
         updated to display the three sets of FHST visibility windows when
         in two-gyro mode
        SMS changes will be minimal and isolated to the FHST
         statements; new arguments (described in the interface section of
         this presentation) will be added to handle the maps and attitude

10/24/2003                                                                     60
             Short-Term Scheduling: PASS

                       Clif Darby
                    Bob McCutcheon

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             HST Scheduling Systems

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                                  PASS Background
        PASS is run weekly as the last step of HST short-term scheduling to
         accept, verify, and expand the weekly science plan (SMS) into stored
         command loads for uplink to the spacecraft
        Major PASS functionality includes
                Verifying vehicle pointing control activities
                Selecting FHST reference stars
                Managing antennas and solar arrays
                Managing science and engineering data recording
                Generating weekly TDRSS communication schedule requests
                Generating stored command loads
                Generating ancillary reports
        PASS FHST Reference Star Selection System (FRSS) is used by the
         guide star selection system for determining roll ranges with valid
         FHST support
10/24/2003                                                                      63
                    PASS TGS Requirements Summary:
                      Vehicle Control Determination

            PASS will determine whether an SMS is in three-
             gyro (nominal) mode or two-gyro (degraded) mode
             based on a data base parameter
            Two-gyro mode further consists of three types of
             vehicle control modes
                M2G control mode (default)
                T2G control mode when under FHST rate control
                F2G control mode when in FGS fine lock

10/24/2003                                                       64
                   PASS TGS Requirements Summary:
                          SMS Statements
       PASS will accept FHST statements to support two-gyro mode
        (described in the interface section of this presentation)
            FHST OAD to perform onboard attitude determination and attitude correction
            FHST GOB to perform two-gyro FHST observer control

       PASS will not allow the following SMS statements in two-gyro
            FHST(MAN) - FHST maneuver update
            FHST(DEL) - FHST delay update
            FHST(OBS) - FHST observer
            GSACQ,CPNAME(REACQ) - Guide star reacquisition
            SLEW,SLEWRATE - Any vehicle slew that specifies the SLEWRATE

10/24/2003                                                                                65
                 PASS TGS Requirements Summary:
                       Attitude Uncertainty

       PASS will use SMS statements and data base values
        to determine three levels of attitude uncertainty
            Large uncertainty always exists during M2G
            Small uncertainty always exists during F2G
            T2G transitions between large, medium, and small
       PASS will account for attitude uncertainty when
        calculating constraints for FHST, V1, off-nominal
        roll, and solar array (shadowing and incidence angle)

10/24/2003                                                      66
                     PASS TGS Requirements Summary:
                         Initial FHST Rate Control

            PASS will verify that an initial rate control
             period exists
                An initial rate control period is a time when a single
                 FHST has continuous visibility before the first FHST
                 OAD statement following a period of M2G control

10/24/2003                                                                67
                      PASS TGS Requirements Summary:
                          Systemic FHST Visibility

        PASS will calculate the periods of systemic FHST
         visibility for use in verifying FHST OAD and
         GSACQ statements
                Systemic FHST visibility is the entire time covered by a
                 collection of FHST visibility windows that overlap by a
                 data-base-specified time

10/24/2003                                                                  68
                PASS TGS Requirements Summary:
              FHST Map / Attitude Correction (1 of 2)
       PASS will determine whether an FHST OAD SMS
        statement is an initial or a second onboard map / attitude
       PASS will verify that an optional second FHST OAD is
        separated from the initial FHST OAD by a data-base-
        specified time (start to start)
       PASS will verify that systemic FHST visibility exists
        from the initial rate control period through a data-base-
        specified time after the start of the FHST OAD
       PASS will verify FHST visibility and issue FHST OAD
10/24/2003                                                           69
                      PASS TGS Requirements Summary:
                    FHST Map / Attitude Correction (2 of 2)
        If the FHST OAD statement does not specify the FHST
                PASS will verify that at least two FHSTs have continuous
                 simultaneous visibility throughout the FHST OAD map
                PASS will verify that at least two FHSTs have visibility
                 throughout the FHST OAD attitude correction
                PASS will optionally populate the FHST OAD command with
                 the PASS-selected FHST
        If the FHST OAD statement specifies the mapping FHST
                PASS will verify the visibility of that FHST and one other
                PASS will populate the FHST OAD command with the specified

10/24/2003                                                                    70
                   PASS TGS Requirements Summary:
                     FHST Observer Commanding

            The FHST GOB statement for observer mode
             commanding may optionally specify the FHST; if an
             FHST is not specified, PASS will select an FHST
            PASS will verify continuous FHST visibility for the
             observer mode and specify the FHST in the command
            PASS will verify that an FHST GOB statement
             accompanies every GSACQ statement and is offset by
             a data-base-specified time

10/24/2003                                                         71
                    PASS TGS Requirements Summary:
                      FGS Acquisition Commanding

            PASS will process GSACQ statements as is done
             currently (reacquisitions not permitted)
            PASS will verify that systemic FHST visibility exists
             from the initial rate control period through a data-
             base-specified time after the start of GSACQ
            If no FHST OAD statements have occurred since the
             previous GSACQ, PASS will verify that systemic
             FHST exists from the previous FGS loss-of-usability

10/24/2003                                                           72
                   PASS TGS Requirements Summary:
                            FHST Maps

            PASS will optionally generate FHST map commands
             on a single FHST and only when that FHST and at
             least one other have visibility
            PASS will schedule automaps to begin as soon as
             possible after the first GSACQ following a type 2
             slew; additional automaps may follow subsequent
             GSACQs if requested
            PASS will, for FHST MAP SMS statements, verify
             that FHST visibility exists for one more FHST than is
             requested in the MAP statement
10/24/2003                                                           73
                    PASS TGS Requirements Summary:
                     FHST Availability Commanding

            PASS will issue FHST shutter open and close
             commands at the start and end of FHST visibility, as
             calculated using the appropriate attitude uncertainty
            PASS will set the FHST available coincident with the
             open shutter command
            PASS will set the FHST as unavailable before the
             close shutter command
            PASS will use the autogroup feature to control these

10/24/2003                                                           74
                     PASS TGS Requirements Summary:
                            PASS Reporting

            PASS will expand existing reports to include
                Calculated FHST visibility windows
                Transition times between M2G, T2G, and F2G
                FHST commanding
                Constraint violations
            PASS will generate error messages when constraint
             violations occur and continue processing if possible

10/24/2003                                                          75
                  PASS TGS Requirements Summary:
                    Star Catalog for Flight Software

            PASS will provide the SKYMAP star catalog to
             flight software for onboard star identification
             and attitude determination

10/24/2003                                                     76
                    TGS Scenario 1 - M2G-T2G-F2G Transition
TGS Mode               M2G
                       M2G                                             T2G T2G                                                F2G


              FHST -- Systemic


Uncertainty                        LARGE (LAU)                      MEDIUM (MAU)                       SMALL (SAU)

                      SLEW 2                     FHST(OAD)                    FHST(OAD)                FHST(GOB)
                              TGS_DUROAD(1)        TGS_DUROAD(4)              TGS_DUROAD(6)
                                  (~3 min)             (7 min)                    (5 min)                TGS_DUROAD(8)
                                                                                                            (8-9 min)
                                             TGS_DUROAD(3)       TGS_DUROAD(5)             TGS_DUROAD(7)
                                                 (3 min)             (3 min)                  (~1-5 min)

                                               = FHST hand-off   Systemic                                   = No hand-off restriction
                 Legend:         SMS
                                                 not allowed     Visibility
                                                                                 = 1 FHST available
                                                                                 = 2 FHSTs available
                    TGS Scenario 2 - F2G-T2G-F2G Transition
TGS Mode                              T2G                 F2G F2G                         T2G                         F2GF2G


              FHST -- Systemic

                                                                            TGS_DUROAD(2) (~1 min)

Uncertainty                                                                  SMALL (SAU)

                                    FHST(GOB)                                                   FHST(GOB)
                                                GSACQ                                                       GSACQ

                                      TGS_DUROAD(8)                                             TGS_DUROAD(8)
                                         (8-9 min)                                                 (8-9 min)
                        TGS_DUROAD(7)                                             TGS_DUROAD(7)
                           (~1-5 min)                                                (~1-5 min)

                                        = FHST hand-off      Systemic                                 = No hand-off restriction
                Legend:       SMS
                                          not allowed        Visibility
                                                                          = 1 FHST available
                                                                          = 2 FHSTs available
                        PASS TGS Design Concept:
       PASS two-gyro support is consistent with overall system design
        and functionality
       Mission scheduling subsystem has most of the software changes
            Pointing control area
                 Occultation processing
                 FHST processing
            Autogroup area
       Data management subsystem has some software changes
            SKYMAP star catalog generation
            PDB processing
       FHST Reference Star Selection System has minimal software
10/24/2003                                                               79
                   PASS TGS Design Concept: Mission
                     Scheduling Subsystem (1 of 3)
       Data structure initialization
            Accept additional SCHF / CRPF data base parameters for two-gyro mode
             (thus minimizing operational impact for transition to two-gyro control)
            Populate internally used parameters with proper values, based on the two-
             gyro or three-gyro data base flag (thus minimizing software algorithm

       Determination of FHST and V1 occultation times
            Invoke the occultation subsystem three times to compute occultation times
             for the entire SMS at each attitude uncertainty level
            Invert occultation times into visibility times
            Use visibility times to verify SMS statements and determine M2G, T2G,
             and F2G modes
            Form one set of visibility times based on calculated M2G, T2G, and F2G
10/24/2003                                                                               80
                      PASS TGS Design Concept: Mission
                        Scheduling Subsystem (2 of 3)
        FHST processing
                Expand FHST SMS statement processing to accept new two-gyro FHST
                 OAD and GOB requests
                     Verify FHST statements using appropriate visibility times
                     Select FHST for use
                     Issue commanding using expanded data base templates
                Disable FHST MAN, OBS, DEL requests, thereby bypassing reference
                 star selection
                Modify FHST map area to handle additional two-gyro constraints

        Pointing control constraints
                No changes needed; handled by proper two- or three-gyro data base

10/24/2003                                                                           81
                     PASS TGS Design Concept: Mission
                       Scheduling Subsystem (3 of 3)

        Autogroup processing
                Add new FHST visibility orbital events for use in generation of FHST
                 shutter open / close and FHST availability commanding
                Apply optional + / - delta for determination of command times
                Allow an optional event identifier for SMS on / off control of a subset of
                 commands for a given event; e.g., turn FHST availability commanding
                 off, but leave FHST shutter commanding on

10/24/2003                                                                                    82
                      PASS TGS Design Concept:
                          Other Subsystems
            Modify project data base subsystem
                Add two-gyro parameters to SCHF and CRPF
                Add new entries in the GREX and DFSC files to define FHST
                 commanding parameters
                Expand the autogroup file format to support FHST shutter and
                 availability commanding
            Generate a SKYMAP reference star catalog for the flight
             software by modifying input generation options for
             limiting star magnitude and proper motion reference time
            Modify FRSS to make reference star selection optional
10/24/2003                                                                      83
             Commanding / PRD

                 Alan Welty
                Mike Bielefeld

10/24/2003                       84
                             Commanding Role
        Create and maintain “instructions” for SMS
                An instruction is invoked by each calendar activity,
                 including FHST updates and GSACQs
                Guided by information on the PMDB, the instruction
                 outputs statements required by the activity to the SMS
                Instructions are written in “Science Commanding
                 Programming Language,” part of SPSS
        Maintain SMS Review Tool (SRT)

10/24/2003                                                                85
                           Commanding Impacts
        Preserve current FHST and GSACQ commanding
        Develop new instructions for new FHST activities
                New activity types expected for OAD and GOB modes

        Adapt existing instructions for new guide star
         acquisition scenarios
                New scenarios expected for two-gyro mode
                May require new instructions as well

        Incorporate two-gyro checks into SRT
10/24/2003                                                           86
                       PRD Data Types

        Commands, telemetry, symbols: Support CCS PRD
        PLCPs, CCLs, and GRPs: Support command scripts
        TFPF tables: Support HST486 personnel
        CRPF and SCHF: Support PASS, SPSS, and TRANS
        GREX, DFSC, and AGCF: PASS only
        DBDF: Support ST-ICD-11 syntax modifications

10/24/2003                                                87
                                  PRD Impacts
       Impact similar to normal software build-related PRD change
       Value changes: Normal process
       Data structure changes
            ICD modifications
            Output specs by receiving party (e.g., SPSS, TRANS)
            IMTOOL changes
            Regenerate PASS ODBs

       Determine data item owner, then values
       Coordinate installation for tests and operations

10/24/2003                                                           88
               Test Planning

             Leslie Zimmerman Foor

10/24/2003                           89
                 Planning and Scheduling
                     System Testing
       The modifications to each of the planning and
        scheduling systems will be tested using the normal
        testing process
       This testing will be successfully completed before
        starting the integration testing of the entire
        planning and scheduling system
       Test cases will be generated for each requirement,
        and their verification will be tracked using the
        DOORS requirements management tool

10/24/2003                                                   90
                    Requirements Traceability
                        and Verification
        Requirements and test cases for two-gyro mode will be managed
         using DOORS; the following diagram illustrates how the test
         cases and requirements will be linked:

10/24/2003                                                               91
                             Integration Testing
            Determine scenarios and create test cases and observations
             for each of them
            Schedule observations on test flight calendars and generate
             SMSs and PASS products
            Verify that no unexpected errors / warnings occur during
             the processing
            Analyze intermediate output to verify that it meets expected
            Perform further verification of the final products using an
             HST simulator (e.g., VEST)

10/24/2003                                                                  92
                           Test Environment

       Integration testing will take place in the integrated
        test environment
            Complete HST planning and scheduling system from
             APT  SMS generation
            Coming soon: PASS processing on Unix
            Separation from subsystem testing data
            Flexibility in P&S subsystem versions
            Supports multiple data bases, .i.e., multiple versions of
             ASSIST and PMDB data bases

10/24/2003                                                               93

             Bob McCutcheon

10/24/2003                    94
             Interface Control Documents

10/24/2003                                 95
                       Science Scheduling to Mission
                      Scheduling (ST-ICD-11) (1 of 2)

            Modify FHST statement for two-gyro operations
                Add new modes for two-gyro control only
                     OAD: Perform onboard attitude determination consisting of an
                      FHST map followed by onboard star identification, attitude
                      determination, and an onboard sized vehicle maneuver to correct
                      the vehicle attitude
                         Optional parameter: FHST map tracker ID

                     GOB: Designate FHST to be used as an observer during two-gyro
                      FGS guide star acquisition
                         Required new parameter: FHST observer support end time

                         Optional parameter: FHST observer tracker ID

10/24/2003                                                                              96
                     Science Scheduling to Mission
                    Scheduling (ST-ICD-11) (2 of 2)
                Restrict existing maneuver (MAN), delay (DEL), and
                 observer (OBS) updates to three-gyro control only
                Permit existing map (MAP) and standby (SBY) modes during
                 both three-gyro and two-gyro control
            Expand AUTO statement to include optional event
             identifier to provide on / off control for a subset of
             command groups associated with an orbital event
            Add new attitude-dependent orbital events for use in
             autogroup commanding
                FxVISBEG indicates start of FHST-x visibility
                FxVISEND indicates end of FHST-x visibility
10/24/2003                                                                  97
                        PASS to Project Data Base
                       (ST-ICD-26, Part 2) (1 of 4)
            Files affected: SCHF, CRPF, DFSC, GREX, and AGCF
            SCHF: Add new spacecraft parameters
                Flag to indicate that two-gyro control is in effect
                Minimum times to establish FHST rate control
                     When transitioning from M2G to T2G mode
                     When already in T2G mode or when transitioning from F2G to
                      T2G mode
                         Defines minimum FHST / FHST visibility overlap for FHST rate-

                          control handoff in T2G mode
                         Defines minimum FGS / FHST visibility overlap for transition
                          from F2G to T2G mode

10/24/2003                                                                                98
                        PASS to Project Data Base
                       (ST-ICD-26, Part 2) (2 of 4)
                For OADs (separate entries for first and second OADs)
                     Minimum time for FHST map
                     Minimum time for attitude correction
                For FHST observer support of FGS guide star acquisition
                     Minimum time for FHST observer to settle
                     Minimum FHST / FGS visibility overlap during initial phase of
                      guide star acquisition

            CRPF: Expand constraint / restriction parameters
                Add support for three levels of attitude uncertainty
                     FHST and V1 Moon angle constraints
                     FHST and V1 Earth bright limb angle constraints

10/24/2003                                                                            99
                        PASS to Project Data Base
                       (ST-ICD-26, Part 2) (3 of 4)
                     FHST and V1 Earth dark limb angle constraints
                     FHST Sun angle constraint (shutter open)
                     FHST Sun angle constraint (shutter closed)
                     V1 Sun angle constraint (aperture door open)
                     V1 Sun angle constraint (aperture door closed)
                Allow separate sets of two-gyro and three-gyro input
                     HST roll parameters (off-nominal roll and SA shadowing
                     Solar array parameters (SA off-nominal incidence angle checking
                      and type 28 command management)
                Note: No CRPF changes for HGA / LGA management

10/24/2003                                                                              100
                        PASS to Project Data Base
                       (ST-ICD-26, Part 2) (4 of 4)
                DFSC and GREX: Add new command templates and PLCP
                 command group names
                     Onboard FHST map, star ID, attitude determination, and attitude
                      correction events
                     FHST observer support of FGS guide star acquisitions
                AGCF
                     Modify format to include optional + / - delta time and event identifier
                      that are used to
                         Adjust command times by a + / - delta relative to their associated

                            orbital events
                         Provide on / off control for a subset of command groups associated
                            with a given orbital event
                     Add new autogroup commanding
                         FHST shutter open and shutter close commands

                         FHST start and end availability commands
10/24/2003                                                                                      101
                      CCS to P&S (HST-ICD-T1)

            Add SKYMAP star catalog definitions
                Ground reference star catalog used by
                   PASS for FHST reference star selection
                   SAC for FHST calibration and fine attitude star identification

                Flight software reference star catalog used for onboard
                 star identification

10/24/2003                                                                           102

             Carey Myers

10/24/2003                 103
                                      Risks (1 of 2)
        SPSS scheduling algorithms are complex, and there are many
         event scenarios to consider; some scenarios may be missed
                Mitigation: Begin design process with definition of scenarios;
                 develop test cases for each
        Overlap of flight software two-gyro work with scheduling
         system software implementation might cause late-breaking
         requirement changes
                Mitigation: Incorporate flexibility into design; parameterize data;
                 implement software in phases, with well-defined areas first
        Onboard testing of two-gyro mode operations does not occur
         until late in the scheduling system software implementation;
         unanticipated design changes may be needed
                Mitigation: Incorporate flexibility into design; parameterize data;
                 incorporate updates in Phase II
10/24/2003                                                                             104
                                        Risks (2 of 2)

        Different occultation algorithms between SPIKE, SPSS, and
         PASS scheduling systems could limit the capability to
         generate two-gyro science plans. Under three-gyro mode,
         FHST visibility mismatches have been minor; for two-gyro
         mode, they may become a significant problem
                Mitigation: Start with CVZ observations to minimize mismatches;
                 ensure that SPSS is more restrictive than PASS; review the study on
                 algorithmic differences; consider integrating SPSS algorithm into
                 PASS (Phase II)
        Pointing error inherent under two-gyro control may cause
         antenna / communications problems
                Mitigation: Consider applying attitude uncertainty to antenna area in
                 PASS; minimize time under large attitude uncertainty
10/24/2003                                                                               105
            Scheduling system issues currently being worked through
                Handling of type 2 slew FHST shutter / availability commanding
                Placement of type 4 slews (Are they allowed before GSACQ?)
                FHST maps / automaps: Are they needed? Should duration be
                Is the second OAD always required? (Currently assuming so)
                FHST / GOB
                     Is it required for every GSACQ, or only the first in the sequence,
                      or at all?
                     Is it before, at, or after GSACQ?
                GSACQ scenario changes unknown
                Earth calibrations: Are they needed in two-gyro? How will they
                 be scheduled?
10/24/2003                                                                                 106
             TGS Project Schedule (1 of 4)

10/24/2003                                   107
             TGS Project Schedule (2 of 4)

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             TGS Project Schedule (3 of 4)

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             TGS Project Schedule (4 of 4)

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             TGS Implementation Schedule (1 of 2)

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             TGS Implementation Schedule (2 of 2)

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                                   Acronyms (1 of 2)
   AGCF      auto-group command data file                   FSE      Flight Systems Engineering
   APT       Astronomer’s Proposal Tools                    FSW      Flight Software
   ASAP      as soon as possible                            GOB      FHST two-gyro observer mode
   asec      arc-seconds                                    GREX     group expansion file
   ASSIST    relational data base for proposals             GRP      CCS real-time command group
   C&C       Calendar & Candidate                           GSACQ    guide star acquisition
   CCB       Configuration Control Board                    GSC      guide star catalog
   CCL       CCS command language                           GUI      graphical user interface
   CCS       Control Center System                          HGA      high-gain antenna
   CL        command loader                                 HST      Hubble Space Telescope
   CMD       Command Maintenance and Development            ICD      interface control document
   CRPF      constraints and restrictions parameters file   ID       identifier
   CT        coarse track                                   IMTOOL   instruction management tool
   CVZ       continuous viewing zone                        LGA      low-gain antenna
   DBDF      data block definition file                     LRP      Long-Range Plan
   DEL       FHST delay mode                                M2G      MSS / two-gyro (mode)
   DFSC      DF-224 / HST486 scenario data file             MAN      FHST maneuver mode
   DOORS     Dynamic Object Oriented Requirements           masec    milliarc-seconds
                  System                                    MGSE     Mission Ground System Engineering
   ESS       Engineering and Software Services              MOSS     Moving Object Support System
   F2G       FGS / two-gyro (mode)                          MSS      magnetic sensing system
   FGS       fine guidance sensor                           ngp      north galactic pole
   FHST      fixed-head star tracker                        NGSS     New Guide Star System
   FL        fine lock                                      OAD      FHST onboard attitude determination mode
   FRSS      FHST Reference Star Selection System           OBAD     onboard attitude determination

10/24/2003                                                                                                      113
                                 Acronyms (2 of 2)
   OBADWG    OBAD working group                           SCS     Science Commanding System
   OBS       observer                                     sgp     south galactic pole
   ODB       operational data base                        SI      Scientific Instrument
   ODM       Operations and Data Management               SM4     servicing mission 4
   OPB       Observation Planning Branch                  SMS     science mission specification
   P&S       planning and scheduling system               SMSG    SMS generation
   PASS      Payload Operations Control Center (POCC)     SPB     Science Projects Branch
                 Applications Software Support            SPIKE   Science Planning Interactive Knowledge
   PCS       pointing control system                                  Environment
   PDB       project data base                            SPSS    Science Planning and Scheduling System
   PI        principal investigator                       SRT     SMS Review Tool
   PLCP      planning command pool file                   SSCB    Spacecraft Scheduling and Commanding
   PMDB      Proposal Management Data Base                            Branch
   PRD       project reference data                       SSDB    Scheduling Systems Development Branch
   PSDB      Planning Systems Development Branch          STScI   Space Telescope Science Institute
   PSEA      pointing and safemode electronics assembly   SU      scheduling unit
   RPS2      Remote Proposal Submission Two               T2G     FHST / two-gyro (mode)
   SA        solar array                                  TDRSS   Tracking and Data Relay Satellite System
   SAA       South Atlantic Anomaly                       TEST    Test Engineering at Space Telescope
   SAC       Sensor Analysis and Calibration              TFPF    table formats and parameters file
   SBY       FHST standby mode                            TGS     two-gyro science
   SCHF      spacecraft characteristics file              TRANS   Transformation
   SCPL      Science Commanding Programming               VEST    Vehicle Electrical System Test
                 Language                                 ZGSP    zero-gyro Sun point

10/24/2003                                                                                                   114

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