 +_____________________________________________________________________
 ] AUTHOR:            ]                             ] DR:              ]
 ] J. ZOPHY           ]    PASS PROGRAM NOTE        ]     52108        ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE:  03/18/83  ]
 ] IBM/282-8409       ]      RELEASE NOTE( )        ] REV A: 09/27/90  ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ] OI20 AND SUBS                 ]  CREW (X)  GROUND ( )  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]        MAJOR SOFTWARE AREA:       ] OPS MODES AFFECTED:             ]
 ]SSW ( )  GNC (X)  VU ( )  SM/PL ( )] G2, G8                          ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA:   ORBIT, DAP                                     ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: 4.35                                           ]
 ]_____________________________________________________________________]
 ] TITLE:  MISCONTROL WITH DOWNFIRING VERNIER JET UNAVAILABLE          ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ] IF A DOWNFIRING VERNIER RCS JET (DVJ) IS UNAVAILABLE, THE ABILITY   ]
 ] OF THE ORBIT DAP TO CONTROL THE VEHICLE'S ATTITUDE IS GREATLY RE-   ]
 ] DUCED WHILE VRCS JETS ARE SELECTED.  SOME DEGREE OF MISCONTROL WILL ]
 ] ENSUE IF ANY SITUATION OCCURS IN WHICH THE BEST JET TO BE FIRED IS  ]
 ] THE UNAVAILABLE JET.  IN SUCH A SITUATION THE ORBIT DAP WILL FIRE   ]
 ] THE NEXT BEST JET, EVEN IF THAT JET FIRING WILL CAUSE UNDESIRABLE   ]
 ] ACCELERATIONS IN ONE OR MORE AXES.                                  ]
 ]                                                                     ]
 ] THE PROBABILITY OF MISCONTROL IS GREATEST DURING SIMULTANEOUS 3-AXIS]
 ] CONTROL IN AUTO MODE (MANEUVER OR ATTITUDE HOLD) OR MANUAL DISCRETE ]
 ] ROTATION SUBMODE.  DURING PERIODS OF THIS TYPE OF CONTROL, THERE IS ]
 ] A TANGIBLE POSSIBILITY OF THE CONTROL SYSTEM (RCS DAP) GOING UN-    ]
 ] STABLE, I.E., LEFT TO ITSELF, THE DAP WOULD NOT BE ABLE TO NULL THE ]
 ] ORBITER'S BODY RATES.                                               ]
 ]_____________________________________________________________________]
 ]USER RESPONSE:                                                       ]
 ] IT IS RECOMMENDED THAT AUTO MODE OR MANUAL DISCRETE RATE SUBMODE NOT]
 ] BE SELECTED WHEN USING VRCS JETS AFTER A DVJ LOSS.  IF VRCS CONTROL ]
 ] IS REQUIRED IN THE PRESENCE OF ONE OR MORE UNAVAILABLE DVJ'S, THEN  ]
 ] DIRECT MANUAL CONTROL USING ROTATION ACCELERATION SUBMODE WOULD BE  ]
 ] THE BEST CHOICE.  KEEP IN MIND THAT FULL AUTOMATIC OR MANUAL CONTROL]
 ] IS AVAILABLE WITH PRIMARY RCS JETS AND THAT THE ALTERNATE PRIMARY   ]
 ] MODE (ALT) CAN BE USED WITH LOADING EFFECTS COMPARABLE TO THOSE     ]
 ] PRODUCED IN VRCS MODE.                                              ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]IBM: PATTI A. THORNTON    DATE 10/16/90]                             ]
 ]    --------------------      ---------]                             ]
 ]FDSD:  SAM ANKNEY         DATE 10/18/90]                             ]
 ]     -------------------      ---------] DARRELL E. STAMPER 11/09/90 ]
 ]PF MGR: K. L. LINDSAY     DATE 10/30/90]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_______________________________________]_____________________________]
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