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! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ! ! SDDL Name: QAOFFSET.SDDL ! ! Purpose: This SDDL file defines the qaoffset relation. ! ! Modification History: ! ! Date OPR Who Reason ! -------- ------- --- ------------------------------------------------- ! 12/ 1/94 27329 EGB Original implementation ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ! ! LANGUAGE FORTRAN, SQL INCLUDE ZSPSS_USER_TYPES.SDDL RECORD QAOFF_TYPE !------------------------------------------------------------------------------ ! ! RECORD INFORMATION ! !------------------------------------------------------------------------------ DESCRIPTION "This relation contains alignment level data that describes the usage of onboard NSSC-1 Offset Maneuver Table Slot offsets by the alignment. Offsets are data stored in the on-board NSSC-1 offset maneuver slot table that are used to perform offset maneuvers. Offset maneuvers correct for target and HST ephemeris errors and/or errors in attitude determined after a target acquisition. So unless the offsets are explicitly cleared by a special activity, the offsets stored in the slot table can be reused when a given target is revisited in scheduling units that can span over several calendars. Because offset slot allocation and offset maneuver activities are scheduled in advance, the need for real time uplinks for such maneuvers is diminished. There are four types of OFFSET activities that are scheduled on a calendar: ALLOCATE, REVERSE, FORWARD, and CLEAR. The REVERSE and FORWARD offset activities are actual offset maneuvers that apply(FORWARD) or back out(REVERSE) target and HST ephemeris corrections and/or target acquisition corrections. The ALLOCATE and CLEAR offset activities are used only in the allocation and deallocation, respectively, of slots in the NSSC-1 offset slot table. Allocate offset activities are scheduled on a calendar for target acquisition alignments that require that a slot be allocated for a specified target acquisition offset. Such target acquisition alignments have QAOFFSET records with QAOFFSET.offset_type=ALL and QAOFFSET.offset_clear_flag=N. Allocate activities have a one second duration and are scheduled sequentially, beginning at the start of the target acquisition alignment. There is no restriction on the order in which these activities appear on a calendar if multiple allocate activities are specified by a single alignment. Forward offset activities are offset maneuvers scheduled in response to an alignment that specifies an offset. These alignments will have QAOFFSET records with offset_type=ACQ or EPH and offset_clear_flag=N. A forward offset maneuver will be scheduled for such an alignment only if - it is the first targeted alignment that follows a GS acquisition. - a GS handoff is required prior to the alignment. - it is NOT the first targeted alignment that follows a GS acquisition AND the previous targeted alignment does not require the same offset. The duration of forward offset maneuvers is dependent on the target position uncertainties specified in QTARGETS and/or the HST vehicle ephermeris error specified in QXPDBCON. Reverse offset maneuvers are scheduled for alignments that do not require an offset that was required by the previous targeted alignment. The maneuver itself reverses the forward maneuver previously applied for the offset. In addition, reverse offset maneuvers will be scheduled for alignments that require an offset and a GS handoff acquisition. The duration of such maneuvers, and the offset magnitudes are set to the values computed for the previously scheduled forward offset maneuver. A reverse offset maneuver will be scheduled prior to an alignment only if - the alignment is not the first targeted alignment that follows a GS acquisition, AND 1. the alignment does not require the same offset specified for the previous targeted alignment, OR 2. a GS handoff is scheduled prior to the alignment and the alignment requires at least one offset. Clear offset activities are scheduled on a calendar for alignments that require that a slot allocated for an offset be cleared or deallocated. Such alignments have QAOFFSET records with offset_type=ACQ or EPH and offset_clear_flag=Y. Clear activities have a duration specified in QXPDBCON and are scheduled sequentially, beginning at the start of the alignment. There is no restriction on the order in which these activities appear on a calendar if multiple clear offset activities are specified by a single alignment." !------------------------------------------------------------------------------ ! ! FIELD INFORMATION ! !------------------------------------------------------------------------------ FIELD proposal_id TYPE PROPOSAL_ID_TYPE FORM NAME "AOF" LABEL "PROPOSAL ID" END_FORM END_FIELD FIELD obset_id TYPE OBSET_ID_TYPE FORM NAME "AOF" LABEL "OBSET ID" END_FORM END_FIELD FIELD alignment_id TYPE ALIGN_ID_TYPE FORM NAME "AOF" LABEL "ALIGN ID" END_FORM END_FIELD FIELD version_num TYPE VERSION_NUM_TYPE FORM NAME "AOF" LABEL "VERSION NUM" END_FORM END_FIELD FIELD offset_id TYPE C12 DESCRIPTION "This field uniquely identifies the offset. It is the concatenation of the proposal id, observation set id, alignment id, and exposure id of the first exposure referenced by the special requirement (the acquisition exposure for target acquisitions), and the offset type ('0' for ephemeris correction, '1'-'Z' for target acquisition)." FORM NAME "AOF" LABEL "OFFSET ID" END_FORM END_FIELD FIELD offset_type TYPE C3 DESCRIPTION "This field identifies the type of offset associated with the activity (offset maneuver or clear offset) to be scheduled: EPHemeris correction ('EPH') or target ACQuisition ('ACQ'). If the alignment contains the target acquisition exposure, then set to 'ALL' to indicate no activity is to be scheduled but a slot is to be ALLocated for subsequent offset usage." FORM NAME "AOF" LABEL "OFFSET TYPE (ALL/ACQ/EPH)" END_FORM DISCRETE " ", "ACQ", "ALL", "EPH" END_FIELD FIELD offset_clear_flag TYPE YES_NO_FLAG_TYPE DESCRIPTION "This field indicates whether or not to schedule a clear offset activity during the alignment instead of an offset maneuver activity before the alignment." FORM NAME "AOF" LABEL "OFFSET CLEAR FLAG (Y/N)" END_FORM END_FIELD FIELD offset_min_mag TYPE I4 UNITS "ARCSECONDS" DESCRIPTION "This field specifies the minimum magnitude (in arcseconds) of the offset used to calculate the duration of the offset." END_FIELD END_RECORD !------------------------------------------------------------------------------ ! ! RELATION DECLARATION ! !------------------------------------------------------------------------------ RELATION qaoffset TYPE QAOFF_TYPE DESCRIPTION "Alignment NSSC-1 Offset Maneuver Usage Relation" SUBSYSTEM_USING "SPSS", "TRANS" FORM NAME "AOF" END_FORM INDEX qaoffset_1 TYPE unique, clustered FIELDS proposal_id, obset_id, alignment_id, version_num, offset_id, offset_type, offset_clear_flag END_INDEX END_RELATION !------------------------------------------------------------------------------ ! ! INSTANCE DECLARATION ! !------------------------------------------------------------------------------ INSTANCE qaoffset GLOBAL TYPE QAOFF_TYPE END_INSTANCE

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