! File: 3995C.PROP ! Database: PEPDB ! Date: 20-FEB-1994:03:07:06 coverpage: title_1: PSEA PASSIVE CHECK FOR RMGA PROCESSING proposal_for: ENG pi_fname: MICHAEL pi_lname: URBAN pi_inst: CODE 441 pi_country: USA num_pri: 1 ! end of coverpage abstract: line_1: This proposal will acquire engineering data to be used line_2: to validate proper scaling and polarities of the outputs line_3: produced by the Pointing and Safemode Electronics line_4: Assembly (PSEA) when the Retrieval Mode Gyro Assembly (RMDA) line_5: is used as the primary rate input sensor. The PSEA provides line_6: the backup attitude control function for the HST in the event line_7: of a serious problem with the DF-224 flight computer. The line_8: PSEA will be placed in test mode which will power the line_9: safemode computer but willinhibit the output of commands to line_10: the reaction wheels and magnetic torquers. Small (5 degrees) line_11: maneuvers will be executed about each vehicle axis to provide line_12: the necessary input from the RMGAs. ! ! end of abstract general_form_proposers: lname: URBAN fname: MICHAEL inst: GFSC/CODE 441 country: USA esa: X ! ! end of general_form_proposers block general_form_text: question: 2 section: 1 line_1: The Pointing and Safemode Electronics Assembly (PSEA) line_2: provides the backup attitude control function in the event line_3: of a serious problem with the DF-224 flight computer. The line_4: PSEA uses sun sensors, rate gyro assembly (RGA), and, line_5: if required, the retrieval mode gyro assembly (RMGA) as line_6: inputs and produces commands to the reaction wheels and line_7: magnetic torquers. It is imperative that the scaling and line_8: polarities of the inputs signals and the output commands be line_9: correct to assure proper performance of the system. Although line_10: phasing tests were performed before launch, and the vehicle line_11: has been under PSEA control before during hardware safemode, line_12: the vehicle has never had to use the RMGA output. The PSEA line_13: Safemode Computer (SMC) is normally powered off. The PSEA, line_14: upon loss of keep-alive signals from the DF-224, will power line_15: on the SMC and the HST will enter hardware sunpoint mode. line_16: Phasing information incorporating the RMGAs can be obtained line_17: on-orbit by utilizing the PSEA test mode. When in test mode line_18: the PSEA will power the SMC and all calculations are per- line_19: formed, however the command outputs are inhibited. ! question: 2 section: 2 line_1: The RGA (rate gyro assembly) null status in the PSEA line_2: Configuration Memory will be changed such that the status line_3: of all RGAs is null; this will cause the PSEA to use the line_4: RMGA as its primary rate input. Once in the loop the RMGA line_5: processing may be verified. ! question: 2 section: 3 line_1: This information is important to provide confidence in the line_2: backup attitude control system. Should problems be line_3: discovered, the entire safemode strategy may change. ! question: 3 section: 1 line_1: Format T is required for all PSEA data takes. The format line_2: T tables will be loaded into the DF-224, dumped and verified. line_3: IMPORTANT NOTE: Format T overlays formats P and F. The line_4: stored program command (SPC) group normally used to initiate line_5: format P can be used to activate T, however if attempts are line_6: made to switch to F format while T is loaded, T format will line_7: be used. Therefore, no switches to F format should line_8: be placed in the command loads following this test for a line_9: reasonable period of time to allow the STOCC to reload P & F. line_11: HST will be slewed to a +V3 to the sun attitude. The RMGA line_12: will be powered up by realtime commands (RTCs) and allowed to line_13: warm up for a minimum of 5 minutes. The RGAs will be nulled line_14: in the PSEA Configuration Memory via RTC, after which the line_15: PSEA will autonomously configure to use the RMGAs in its line_16: control loop when test mode is entered. Safemode Computer line_17: A will be used. ! question: 3 section: 2 line_1: A minimum of 5 minutes after entry into orbit day the STOCC line_2: will begin issuing soft keep-alive disable commands to the line_3: PSEA to condition the PSEA relays to allow entry into hard- line_4: ware sunpoint upon exiting test mode should the DF-224 keep- line_5: alive signals stop while the PSEA is in the test mode. These line_6: commands are automatically issued every 30 seconds by the on- line_7: line system. The PSEA test mode will be commanded by RTC. A line_8: five degree slew about the +V3 axis will be executed from line_9: SPC. This will be followed up by similar slews about the -V3 line_10: +V2,-V2,+V1, and -V1 axes in that order. Ideally, these line_11: slews will be back to back, but may be spread apart subject line_12: to the constraints given below. When the final slew is line_13: complete, test mode and soft keep-alive disable commands will line_14: be terminated. If the slews are spread apart in time by a line_15: significant amount and/or continuous forward link is not line_16: available, test mode initiate and sot keep-alive disable line_17: commands will be terminated between slews. ! question: 3 section: 3 line_1: Constraint 1: Continuous forward link is required whenever line_2: the PSEA is in test mode. This is necessary to keep the soft line_3: keep-alive disable commands and the test mode initiate line_4: commands going. line_5: CONSTRAINT 2: The HST must be in full sunlight whenever test line_6: mode is active. Test mode is active for 73 secs following the line_7: test mode initiate command. This is required to prevent the line_8: PSEA from closing the aperture door when test mode is line_9: initiated. line_10: Constraint 3: The test period must occur no earlier than line_11: Wednesday of the week in which it is scheduled, and must line_12: occur between the hours of 8 AM to 8 PM EST. line_13: An additional set of six slews will be scheduled in the next line_14: orbit as contingency time in the event of a loss of forward line_15: link in the first orbit. line_16: After completion of test mode the RMGA will be powered off. line_17: The previous RGA null/not null configuration will be line_18: restored to the PSEA Configuration Memory. Format F and P line_19: tables will then be uplinked and verified. ! question: 5 section: 1 line_1: Six slews required to obtain a complete set of vehicle line_2: rotations. Since loading format "T" does impact operations line_3: by eliminating the possibility of using "P" and "F" formats, line_4: backup data takes are requested so that the test is assured line_5: of a good probability of success. This test is intended to line_6: exerise the last untested loop in the PSEA and should not line_7: again be necessary. ! question: 6 section: 1 line_1: Continuous forward link required whenever the PSEA is in line_2: test mode is required to keep it in test mode. The PSEA line_3: will automatically exit out of the test mode, 73 secs. line_4: after the test mode initiate command is received. line_5: The PSTOL proc issues this command every 73 secs. ! question: 7 section: 1 line_1: Results will be processed by the ESS system and compared line_2: against predicted values supplied by LMSC, along with line_3: comparisions with attitude from the DF-224. ! question: 8 section: 1 line_1: The time constaints given in Constraint 3 above are requested line_2: to allow STOCC engineers time for a Flight Readiness Review line_3: of the test procedure immediately prior to the test itself, line_4: and to allow the test to occur during regular business hours line_5: to maximize personnel availability should they be required line_6: due to a contingency. ! !end of general form text general_form_address: lname: URBAN fname: MICHAEL category: PI inst: GFSC/CODE 441 addr_1: GSFC city: GREENBELT state: MD zip: 20771 phone: 286-1335 ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: NEP descr_1: N.ECLIPTIC POLE (NOMINAL) WITH +V3 TO SUN pos_1: RA = 18.033D +/- .1", pos_2: DEC = +66.56086D +/- .01" equinox: 1992 ! targnum: 3 name_1: NEP-3 descr_1: N.ECLIPTIC POLE-3 (NOMINAL) WITH +V3 TO SU descr_2: N pos_1: RA = 18.033D +/- .1", pos_2: DEC = +66.56086D +/- .01" equinox: 1992 ! targnum: 4 name_1: NEP-2 descr_1: N.ECLIPTIC POLE-2 (NOMINAL) WITH +V3 TO SU descr_2: N pos_1: RA = 18.033D +/- .1", pos_2: DEC = +66.56086D +/- .01" equinox: 1992 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.000 targname: NEP config: S/C opmode: POINTING aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO req_1: CYCLE 1 / 1-19; comment_1: SLEW TO TARGET SEP AND SLEW comment_2: SOLAR ARRAYS +/- 3 DEGREES TO comment_3: SUN NORMAL VIA SPC comment_4: THE SIX SLEWS SHOULD BE CENTERED comment_5: AROUND ORBIT NOON. ! linenum: 2.000 targname: NEP config: S/C opmode: DATA aperture: V1 num_exp: 1 time_per_exp: 25M fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO req_1: AFTER 1 BY 10M+/-5M; req_2: RT ANALYSIS; req_3: REQ UPLINK; comment_1: UPLINK REQ'D TO DUMP ETR. comment_2: LOAD AND DUMP "T" FORMAT comment_3: AND TO PATCH SUN ANGLE comment_4: SA NORMAL SAEMODE LIMIT TO comment_5: 12 DEGREES VIA RT COMMAND ! linenum: 3.000 targname: NEP config: S/C opmode: POINTING aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_1: AFTER 2 BY 20M+/-5M; comment_1: SWITCH TO "T" FORMAT VIA comment_2: SPC, USING MOCMERGE SMS ! linenum: 4.000 targname: NEP config: S/C opmode: DATA aperture: V1 num_exp: 1 time_per_exp: 20M fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_1: AFTER 3 BY 10M+/-5M; req_2: RT ANALYSIS; comment_1: REALTIME UPLINK REQ'D TO COMMAND comment_2: POWER ON TO RMGA'S AND TO SELECT comment_3: REQUIRED TLMDIAGS IN PSEA ! linenum: 5.000 sequence_1: DEFINE sequence_2: PSEA-A targname: NEP config: S/C opmode: POINTING aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_1: SEQ 5-8 NO GAP; req_2: CRIT OBS; comment_1: COLLECT/REC "T" DATA comment_2: FROM BEG. #5 TO END #8. comment_3: LINES 5-8 TO BE PERFORMED comment_4: IN ONE SUNLITE ORBIT. ! linenum: 6.000 sequence_1: DEFINE sequence_2: PSEA-A targname: NEP config: S/C opmode: DATA aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_1: RT ANALYSIS; req_2: REQ UPLINK; comment_1: FROM BEGINNING OF 6 TO comment_2: END OF 8; comment_3: R/T UPLINK REQUIRED TO COMMAND comment_4: PSEA TEST MODE. ! linenum: 7.000 sequence_1: DEFINE sequence_2: PSEA-A targname: NEP-2 config: S/C opmode: POINTING aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_2: CRIT OBS; comment_1: SLEW TO TARGET +5 DEGREES ABOUT comment_2: V3 VIA SPC ! linenum: 8.000 sequence_1: DEFINE sequence_2: PSEA-A targname: NEP config: S/C opmode: POINTING aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_2: CRIT OBS; comment_1: SLEW TO TARGET SEP (NOMINAL) comment_2: -5 DEGREES ABOUT V3 VIA SPC comment_3: LINES 8 MUST BE COMPLETED NO comment_4: LATER THE 5 MIN. PRIOR TO comment_5: ENTER ORBIT NIGHT. ! linenum: 9.000 sequence_1: DEFINE sequence_2: PSEA-A targname: NEP config: S/C opmode: POINTING aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_1: CRIT OBS; req_2: SEQ 9-12 NO GAP; req_3: SEQ 9-12 NON-INT; comment_1: COLLECT/REC FORMAT "T" DATA comment_2: FROM BEGINNING OF 9 TO THE comment_3: END OF 12. LINES 9 THROUGH comment_4: 12 MUST BE PERFOMED DURING comment_5: ONE SUNLIGHT ORBIT. ! linenum: 10.000 sequence_1: DEFINE sequence_2: PSEA-A targname: NEP config: S/C opmode: DATA aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_1: CRIT OBS; req_2: RT ANALYSIS; comment_1: R/T ANALYSIS FROM BEGINNING comment_2: OF 10 TO END OF 12. R/T UPLINK comment_3: REQUIRED TO COMMAND PSEA TEST MODE ! linenum: 11.000 sequence_1: DEFINE sequence_2: PSEA-A targname: NEP-3 config: S/C opmode: POINTING aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_1: CRIT OBS; comment_1: SLEW TO TARGET +5 DEGREE ABOUT comment_2: V2 VIA SPC ! linenum: 12.000 sequence_1: DEFINE sequence_2: PSEA-A targname: NEP config: S/C opmode: POINTING aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_1: CRIT OBS; req_2: AFTER 11 BY 5M +/- 3M; comment_1: SLEW TO TARGET SEP (NOMINAL) comment_2: -5 DEGREE ABOUT V2 VIA SPC. comment_3: LINE 12 MUST BE COMPLETED NO comment_4: LATER THAN 5 MIN. PRIOR TO comment_5: ENTER ORBIT NIGHT. ! linenum: 13.000 sequence_1: DEFINE sequence_2: PSEA-A targname: NEP config: S/C opmode: POINTING aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_1: CRIT OBS; req_2: SEQ 13-16 NO GAP; req_3: SEQ 13-16 NON-INT; comment_1: COLLECT/REC FORMAT "T" DATA comment_2: FROM BEGINNING OF 13 TO THE comment_3: END OF 16. LINES 13 THROUGH comment_4: 16 MUST BE PERFOMED DURING comment_5: ONE SUNLIGHT ORBIT. ! linenum: 14.000 sequence_1: DEFINE sequence_2: PSEA-A targname: NEP config: S/C opmode: DATA aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_1: CRIT OBS; req_2: RT ANALYSIS; comment_1: R/T ANALYSIS FROM BEGINNING comment_2: OF 14 TO END OF 16. R/T UPLINK comment_3: REQUIRED TO COMMAND PSEA TEST MODE ! linenum: 15.000 sequence_1: DEFINE sequence_2: PSEA-A targname: NEP config: S/C opmode: POINTING aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_1: CRIT OBS; req_2: ORIENT 5D +/- 0.5D req_3: FROM NOMINAL; comment_1: SLEW TO TARGET +5 DEGREE ABOUT comment_2: V1 AXIS VIA SPC ! linenum: 16.000 sequence_1: DEFINE sequence_2: PSEA-A targname: NEP config: S/C opmode: POINTING aperture: V1 num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO, req_1: CRIT OBS; req_2: AFTER 15 BY 5M +/- 3M; comment_1: SLEW TO TARGET SEP (NOMINAL) comment_2: -5 DEGREE ABOUT V1 AXIS TO NOMINAL comment_3: VIA SPC. LINE 16 MUST BE COMPLETED comment_4: NO LATER THAN 5 MIN. PRIOR TO comment_5: ENTER ORBIT NIGHT. ! linenum: 17.000 sequence_1: USE sequence_2: PSEA-A ! linenum: 17.500 sequence_1: USE sequence_2: PSEA-A comment_1: AT 1ST OPPORTUNITY REPEAT THE comment_2: RECORDING OF "T" FORMAT. DURING comment_3: PSEA TEST MODE FOR THE SIX DEGREE comment_4: SLEWS ABOUT V1,V2, AND V3. ! linenum: 18.000 targname: NEP config: S/C opmode: DATA aperture: V1 num_exp: 1 time_per_exp: 15M fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO req_1: RT ANALYSIS; req_2: REQ UPLINK; comment_1: R/T UPLINK REQ'D TO POWER OFF comment_2: RMGA'S AND CHANGE GYRO'S 1,2,3,5 comment_3: TO NOT NULL CONFIGURATION ! linenum: 19.000 targname: NEP config: S/C opmode: DATA aperture: V1 num_exp: 1 time_per_exp: 15M fluxnum_1: 1 priority: 1 param_1: CONTROL=GYRO req_1: RT ANALYSIS; req_2: REQ UPLINK; comment_1: R/T UPLINK REQ'D TO PATCH SUN ANGLE comment_2: SA NORMAL SAFEMODE LIMIT TO 9 DEGREES comment_3: AND TO LOAD AND DUMP C AND F comment_4: TELEMENTRY FORMATS ! ! end of exposure logsheet ! No scan data records found