 +_____________________________________________________________________
 ] AUTHOR:            ]                             ] DR:              ]
 ] W. ALLEN           ]    PASS PROGRAM NOTE        ]    57330         ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: SEPT. 1987 ]
 ] DEV/282-7344       ]      RELEASE NOTE( )        ]                  ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ] OI06 AND SUBS                 ]  CREW (X)  GROUND ( )  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]        MAJOR SOFTWARE AREA:       ] OPS MODES AFFECTED:             ]
 ]SSW ( )  GNC (X)  VU ( )  SM/PL ( )] G2                              ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA: OMS                                              ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: 4.35                                           ]
 ]_____________________________________________________________________]
 ] TITLE:                                                              ]
 ] MANUAL OMS SHUTDOWN                                                 ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:  THE ORBIT DAP DOES NOT INITIATE ATTITUDE HOLD AT      ]
 ] MANUAL OMS CUTOFF AS IT DOES AT GUIDED CUTOFF.  INSTEAD, IT RETAINS ]
 ] GUIDANCE AS THE COMMAND SOURCE, AND WILL INITIATE ATTITUDE HOLD AT  ]
 ] THE +X RCS BURN ATTITUDE, TO ALLOW BURN COMPLETION USING RCS.       ]
 ]     UNNECESSARY JET FIRINGS MAY RESULT IF THE OMS ENGINES ARE       ]
 ] MANUALLY DISARMED DURING A BURN IN OPS 2.  SOME JET FIRINGS WILL    ]
 ] OCCUR IF ANY ATTITUDE ERROR AT SHUTDOWN IS GREATER THAN THE RCS     ]
 ] ATTITUDE DEADBAND IN EFFECT IMMEDIATELY AFTER THE BURN.  DEPENDING  ]
 ] UPON THE GEOMETRY OF A GIVEN BURN, THESE FIRINGS COULD BE IN CURRENT]
 ] DIRECTION (I.E., TOWARDS THE +X RCS BURN ATTITUDE) OR THE WRONG     ]
 ] DIRECTION.  REGARDLESS, EVENTUALLY THE ORBITER WILL MAINTAIN THE RCS]
 ] BURN ATTITUDE.                                                      ]
 ]     IT IS POSSIBLE THAT THE PROBLEM MAY MANIFEST ITSELF IN THE FORM ]
 ] OF A SEQUENCE OF FIRINGS IN OPPOSITE DIRECTIONS, A "DOUBLE          ]
 ] MANEUVER", IN WHICH AN INITIAL FIRING DRIVES THE ORBITER TOWARD THE ]
 ] FINAL TVC COMMANDED ATTITUDE, A SECOND FIRING (WHICH OCCURS WHEN THE]
 ] DAP RECEIVES FROM GUIDANCE THE QUATERNION BASED UPON THE RCS        ]
 ] PROPULSION SYSTEM) REVERSES THE BODY RATE IMPARTED BY THE FIRST, AND]
 ] A THIRD FIRING STOPS THE MANEUVER AT THE RCS COMMANDED ATTITUDE.    ]
 ]     (NOTE: THE GUIDANCE COMMANDED ATTITUDE QUATERNION IS BASED UPON ]
 ] THE OMS ENGINE GEOMETRY FOR TVC BURNS; IT IS BASED UPON THE +X RCS  ]
 ] GEOMETRY DURING GUIDED RCS BURNS.)                                  ]
 ]_____________________________________________________________________]
 ] USER RESPONSE:  BECAUSE THE ORBITER ATTITUDE WILL EVENTUALLY LINE UP]
 ] WITH THE RCS BURN ATTITUDE, NO ACTION IS NECESSARY.  IF DESIRED, THE]
 ] LIKELIHOOD OF UNNECESSARILY FIRING JETS CAN BE REDUCED OR ELIMINATED]
 ] BY INCREASING THE RCS ATTITUDE DEADBAND WHICH WILL BE IN EFFECT     ]
 ] AFTER THE BURN (MAX. ALLOWED IS 40.0 DEG).                          ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]IBM: WYATT COOPER         DATE 7/28/88 ]                             ]
 ]    --------------------      ---------]                             ]
 ]SSD: SAM ANKNEY           DATE 7/28/88 ]                             ]
 ]    --------------------      ---------] RW MOOREHEAD        7/30/88 ]
 ]PF MGR: KL LINDSAY        DATE 7/29/88 ]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_______________________________________]_____________________________]
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