 +_____________________________________________________________________
 ] AUTHOR:            ]                             ] DR:              ]
 ] CHRIS HICKEY       ]    PASS PROGRAM NOTE        ]       110333     ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE:            ]
 ] SSOAS/(281)335-2273]      RELEASE NOTE( )        ]       01/29/97   ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ]   OI-26B, OI-27               ]  CREW ( )  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]        MAJOR SOFTWARE AREA:       ] OPS MODES AFFECTED:             ]
 ]SSW ( )  GNC (X)  VU ( )  SM/PL ( )]  G2, G8                         ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA: NAV, IMU, GPC                                    ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: 4.97                                           ]
 ]_____________________________________________________________________]
 ] TITLE:                                                              ]
 ]         GPC ERROR(S) CAUSED BY HIGH IMU GIMBAL RATES                ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ]    ONE OR MORE GPC ERRORS (GROUP=4, CODE=10 AND PDE=GEK_ORBIT_MFE)  ]
 ] COULD OCCUR AT 6.25 HZ IN THE QUAT_TO_EULER PROCEDURE DURING        ]
 ] PERIODS OF HIGH IMU GIMBAL RATES.  THESE ERRORS RESULT FROM AN      ]
 ] ATTEMPT TO TAKE THE ARCSIN OF A VALUE GREATER THAN ONE WHILE        ]
 ] EXTRACTING TOPODETIC EULER ANGLES FROM THE BODY TO TOPODETIC        ]
 ] QUATERNION.  THE ERROR OCCURS WHEN THE BODY TO M50 QUATERNION       ]
 ] BECOMES UNNORMALIZED DUE TO HIGH IMU GIMBAL RATES.  HIGH IMU GIMBAL ]
 ] RATES MAY BE OBSERVED DURING PERIODS OF HIGH VEHICLE RATES AND WHEN ]
 ] THE PITCH GIMBAL ON AN IMU APPROACHES 90 OR 270 DEGREES.  GPC ERRORS]
 ] WILL ONLY OCCUR WHEN A HIGH RATE EXISTS ON THE SELECTED IMU.        ]
 ]    WHEN THESE GPC ERRORS OCCUR, DISCONTINUITIES IN THE TOPODETIC    ]
 ] ANGLES WHICH FORM THE GPS AIDING STATE ARE LIKELY.  THESE           ]
 ] DISCONTINUITIES SHOULD NOT PERSIST FOR MORE THAN A FEW SECONDS AND  ]
 ] SHOULD NOT ADVERSELY AFFECT THE PERFORMANCE OF THE GPS RECEIVER.    ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ]USER RESPONSE:                                                       ]
 ]                                                                     ]
 ] BE AWARE OF THE ABOVE.                                              ]
 ]                                                                     ]
 ] GPC ERRORS ARE ONLY VISIBLE IN DOWNLIST.                            ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]SSOAS:  JOHN MAGLEY       DATE 03/18/97]                             ]
 ]      ------------------      ---------]                             ]
 ]ASD:  ERIC C. BINGHAM     DATE 03/19/97]                             ]
 ]    --------------------      ---------]                             ]
 ]PF MGR:                   DATE         ]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_______________________________________]_____________________________]
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