 +_____________________________________________________________________
 ] AUTHOR:            ]     RECONFIGURATION         ] DR:  107119      ]
 ] J. MCKENNA         ]       PROGRAM NOTE          ]                  ]
 ]____________________]                             ]------------------]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE:  12/09/92  ]
 ] RSOC/483-4390      ]      RELEASE NOTE( )        ] REV B: 08/16/93  ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ] OI-21 & SUBS                  ]  CREW (X)  GROUND (X)  DUMP ONLY ( )]
 ]                               ]                                     ]
 ]---------------------------------------------------------------------]
 ] MAJOR SOFTWARE AREA:    PASS(X) BFS( )] OPS MODES AFFECTED:         ]
 ] SSME**( ) DEU**( ) T&G( ) DFL/FPL**( )] G9, S2                      ]
 ] TFL**( ) TCS**( ) I-LOAD( ) LEVEL C(X)]                             ]
 ]---------------------------------------------------------------------]
 ] SOFTWARE SUB-AREA: FDA, SM/PL                                       ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: JSC19478-54/S 7.20, 7.21, 7.6                  ]
 ]                      SS-P-0002-580/S 4.1                            ]
 ]_____________________________________________________________________]
 ] TITLE:  UNEXPECTED PAYLOAD FDA MESSAGE                              ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ] DURING IUS MISSION VEHICLE TESTS, AN UNEXPECTED FDA MESSAGE "205    ]
 ] TDRS XMIT ON A" OCCURRED WHEN THE PAYLOAD WAS POWERED ON AS WELL    ]
 ] AS WITH THE PAYLOAD POWERED OFF DURING THE GROUND TESTS FOR BOTH    ]
 ] STS29 AND 54). THIS LED TO AN ANALYSIS THAT REVEALED THAT AN INITIAL]
 ] LOCK ON PAYLOAD DATA VIA DECOMS 2, 3 OR 4 MAY CAUSE A CONDITION     ]
 ] WHERE THE SECOND PL DATA SYNCH WORD IS ERRONEOUSLY STORED IN THE    ]
 ] PDI DATA RAM, OVERWRITING THE DATA THERE. IF THE DATA IN THAT LOCAT-]
 ] ION HAS AN ASSOCIATED FDA, THEN THE CHANGED DATA MAY CAUSE UNEXPECT-]
 ] ED FDA. THE ACTUAL RAM ADDRESS AFFECTED IS A FUNCTION OF THE DFL    ]
 ] LOADED IN THE DECOM. CONSEQUENTLY, ANY MEMORY LOCATION COULD BE AF- ]
 ] FECTED NOT JUST THOSE ASSOCIATED WITH THE PL DATA STREAM JUST INIT- ]
 ] IALIZED/LOCKED ON. THIS COULD OCCUR WITH ANY PAYLOAD USING A PDI.   ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ]USER RESPONSE:                                                       ]
 ]THIS CONDITION IS DUE TO AN UNCERTAIN LOGIC STATE OF A COMPONENT IN  ]
 ]THE LOGIC OF DECOM'S 2, 3 OR 4 AT PDI POWER UP. THIS ANOMALY CAN OC- ]
 ]CUR ONLY ONCE/DECOM (THE COMPONENT THEN GOES TO DESIRED STATE) UNLESS]
 ]THE PDI POWER IS CYCLED. IF THE PAYLOAD DATA AFFECTED IS ACTIVE, VAL-]
 ]ID PAYLOAD DATA WILL OVERWRITE THE CORRUPTED DATA WITHIN ONE INPUT   ]
 ]DATA CYCLE PERIOD. THE GROUND (POCC) CAN CONFIRM VALID PAYLOAD DATA/ ]
 ]ERRONEOUS FDA, OR OTHER INDICATION. IF THE PAYLOAD IS NOT ACTIVE, THE]
 ]FDA MESSAGE WILL BE ANNUNCIATED ONLY ONCE AND THE CORRUPTED DATA WILL]
 ]REMAIN IN THE PDI DATA RAM. NO CREW ACTION IS REQUIRED.              ]
 ]---------------------------------------------------------------------]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]RSOC:   B. CONTRERAS      DATE 09/14/93]                             ]
 ]     -------------------      ---------]                             ]
 ]MOD:   WANDA L. PRICE     DATE 09/14/93]                             ]
 ]    --------------------      ---------] DARRELL E. STAMPER 09/14/93 ]
 ]SW MGR:  CHARLES STOUGH   DATE 09/14/93]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_______________________________________]_____________________________]
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