1+_____________________________________________________________________
 ] AUTHOR:            ]                             ] DR:              ]
 ] R. K. PAIR         ]    PASS PROGRAM NOTE        ]      106678      ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE:            ]
 ] IBM/282-8463       ]      RELEASE NOTE( )        ]       11/24/93   ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ] OI-21 AND SUBS                ]  CREW ( )  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]        MAJOR SOFTWARE AREA:       ] OPS MODES AFFECTED:             ]
 ]SSW ( )  GNC (X)  VU ( )  SM/PL ( )] G6                              ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA: GPC, ABORT, NAV                                  ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: 4.20                                           ]
 ]_____________________________________________________________________]
 ] TITLE:                                                              ]
 ] POTENTIAL GPC ERRORS DURING RTLS FLYBACK                            ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ] DURING THE FLYBACK PHASE OF AN RTLS ABORT WHEN THE VEHICLE NEARS    ]
 ] ZERO DOWNRANGE VELOCITY, THE ARCSIN ARGUMENT IN THE FLT_PATH_ANG    ]
 ] CALCULATION (IN THE POWERED RTLS USER PARAMETER CALCULATION OF      ]
 ] THE RTLS UPP) MAY BE GREATER THAN 1.  THIS CAN OCCUR WHEN THE       ]
 ] THE RELATIVE MOTION OF THE VEHICLE IS APPROXIMATELY TOWARDS THE     ]
 ] CENTER OF THE EARTH, AND WILL OCCUR WHEN THE ESTIMATED ALTITUDE     ]
 ] RATE EXCEEDS THE RELATIVE VELOCITY MAGNITUDE.                       ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ]USER RESPONSE:                                                       ]
 ]                                                                     ]
 ] IGNORE GPC ERRORS EXPERIENCED WHEN THE VEHICLE BEGINS FLYING BACK   ]
 ] TOWARD THE LAUNCH SITE DURING AN RTLS ABORT, IF ANALYSIS CONFIRMS   ]
 ] THAT THE SOURCE IS AN ARCSIN ARGUMENT OUT OF RANGE (ERROR GROUP 4,  ]
 ] CODE A) IN THE MID-FREQUENCY EXECUTIVE.                             ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]IBM:   HUGH D. STOVALL    DATE 01/06/94]                             ]
 ]    --------------------      ---------]                             ]
 ]FDSD:   W. R. PRUETT      DATE 01/06/94]                             ]
 ]     -------------------      ---------] DARRELL E. STAMPER 01/07/94 ]
 ]PF MGR:   M. N. MONTEZ    DATE 01/07/94]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_______________________________________]_____________________________]
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