 +_____________________________________________________________________
 ] AUTHOR:            ]                             ] DR:              ]
 ] J. H. CHUAN        ]    PASS PROGRAM NOTE        ]      55328       ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: SEPT. 1987 ]
 ] IBM/282-8937       ]      RELEASE NOTE( )        ] REV A: 11/05/90  ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ] OI20 AND SUBS                 ]  CREW (X)  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]        MAJOR SOFTWARE AREA:       ] OPS MODES AFFECTED:             ]
 ]SSW ( )  GNC (X)  VU ( )  SM/PL ( )] G3                              ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA: ABORT, OPS, TRANSITIONS                          ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: 4.127                                          ]
 ]_____________________________________________________________________]
 ] TITLE:                                                              ]
 ]        VELOCITY ERRORS DUE TO DELAY IN TAL OPS 3 TRANSITION         ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ] IF G3 ARCHIVE IS USED FOR A TAL OPS 3 TRANSITION THE FOLLOWING NOTE ]
 ] IS NOT APPLICABLE (SINCE IT WILL TAKE A SHORTER TIME TO START OPS   ]
 ] 3 FSW CODE EXECUTION).                                              ]
 ]                                                                     ]
 ] UPON ENTERING OPS 3, THE ENTRY NAVIGATION STATE VECTOR IS INI-      ]
 ] TIALIZED BY PROPAGATING THE LAST VECTOR FROM THE PREVIOUS OPS       ]
 ] FORWARD TO CURRENT TIME.  SINCE NO IMU DATA IS AVAILABLE DURING     ]
 ] THE TRANSITION PERIOD, AN ATMOSPHERIC DENSITY MODEL WHICH ASSUMES   ]
 ] LIFT TO BE ZERO IS USED TO ESTIMATE DRAG ACCELERATION.  HOWEVER,    ]
 ] AS THE ALTITUDE DECREASES BELOW ABOUT 270K FT. THE MODEL BECOMES    ]
 ] HIGHLY INACCURATE, OVERESTIMATING THE DENSITY AND HENCE THE DRAG    ]
 ] ACCELERATION.  THE PROBLEM IS MADE WORSE IF THE TRANSITION TIME     ]
 ] IS EXTENDED BECAUSE OF MMU FAILURES.  THEREFORE, IF THE OPS 3       ]
 ] INITIALIZATION TAKES PLACE TOO LOW IN THE ATMOSPHERE, THE NAVIGATION]
 ] WILL BE INITIALIZED WITH ERRORS THAT MAY BE LARGE ENOUGH TO CAUSE   ]
 ] LOSS OF CONTROL.                                                    ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] USER RESPONSE:                                                      ]
 ] DO NOT DELAY TAL DECLARE AND OPS 3 TRANSITION IF G3 ARCHIVE         ]
 ] RETRIEVE IS DISABLED.                                               ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]IBM: PATTI A. THORNTON    DATE 01/15/91]                             ]
 ]    --------------------      ---------]                             ]
 ]FDSD:  ROBERT N. HINSON   DATE 01/16/91]                             ]
 ]     -------------------      ---------] DARRELL E. STAMPER 01/22/91 ]
 ]PF MGR: MOISES N. MONTEZ  DATE 01/18/91]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_______________________________________]_____________________________]
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