karn@eagle.UUCP (06/04/83)
UOSAT SPACECRAFT CONTROL CENTRE UNIVERSITY OF SURREY, GUILDFORD, SURREY, ENGLAND ************************************************ **** UOSAT BULLETIN-27 1200 GMT 3 JUNE 1983 **** ** OSCAR-8 NEWS ** THE AMSAT-OSCAR-8 SPACECRAFT WAS ACTIVATED IN MODE-J ON 2 JUNE FOLLOWING A BATTERY RECHARGE PERIOD. THE TRANSPONDER OPERATED CORRECTLY ON THE FIRST ORBIT WITH AN INITIAL BATTERY TELEMETRY COUNT OF 364. BY THE NEXT ORBIT THE BATTERY COUNT HAD FALLEN TO 329 AND AO-8 WAS SUBSEQUENTLY COMMANDED TO MODE-D (RECHARGE). THE MODE-A TRANSPONDER HAS BEEN ACTIVATED FOR SHORT PERIODS TO GATHER TELEMETRY, BUT AS THE BATTERY COUNT WAS STILL LOW THE SPACECRAFT WILL REMAIN IN MODE-D RECHARGE, EXCEPT FOR SHORT PERIODS WHEN THE MODE-A TRANSPONDER WILL BE ACTIVATED TO GATHER TELEMETRY. **IT IS ESSENTIAL THAT YOU DO NOT USE OSCAR-8 IF YOU SHOULD HEAR IT ON DURING THIS PERIOD** ** UOSAT NEWS ** AS REPORTED BY A NUMBER OF CORRESPONDENTS DURING THE WEEK, THE MEMORY ERROR RECOVERY COUNTER BITS IN THE TELEMETRY FRAME COULD BE SEEN COUNTING RAPIDLY WHILE THE BULLETIN WAS RUNNING LAST WEEKEND. THE BULLETIN PROGRAM (WITH A 19 HOUR TIMING LOOP) WAS RE-RUN ON WEDNESDAY 1/6/83, AND THE COUNTING DID NOT RECUR. OUR ANALYSIS OF THE SITUATION IS THAT A SOFT ERROR OCCURRED IN A BYTE WHICH WAS ACCESSED VERY FREQUENTLY BY THE BULLETIN PROGRAM AND THIS WAS HAMMING-CORRECTED EACH TIME IT WAS READ DURING THE WEEKEND. THE NON-RECURRENCE DURING A RERUN OF THE PROGRAM INDICATES NO PERMANENT MEMORY FAULT. THANKS FOR THE REPORTS ABOUT THIS EVENT. THE SPACECRAFT REMAINS STABLE IN A FLAT (END OVER END) SPIN WITH A +Y/-Y FACET TEMPERATURE GRADIENT OF AROUND 65C. ANALYSIS OF THE SCIENTIFIC AND NAVIGATION MAGNETOMETER DATA HAS SHOWN THAT THE TIP MASS Z-AXIS IS ORIENTED AT 93 DEGREES TO THE SPACECRAFT Z-AXIS. THE OFFSET BOOM DEPLOYMENT HAS CAUSED THE EFFECTIVE Z-SPIN AXIS TO SHIFT 6 DEGREES FROM THE SPACECRAFT Z-AXIS. INVESTIGATION OF THE BENT BOOM SITUATION HAS INVOLVED A NUMBER OF DEPLOYMENTS AND RETRACTIONS OF THE BOOM TO ESTIMATE THE CHANGE IN POSITION OF THE TIP MASS. THE EFFECTS OF TWO 25CM EXTENSIONS OF THE BOOM HAVE BEEN MINIMAL, AND A FURTHER DEPLOYMENT OF 50CM WAS PERFORMED ON 02/06/83. THE RESULTS OF THIS ARE STILL BEING ANALYSED, BUT NO CHANGE WILL LEAD TO RETRACTION TESTS BEFORE ABANDONING FURTHER RECOVERY ATTEMPTS. DETAILS OF THE WHOLE-ORBIT TELEMETRY RECORDING PROGRAM ARE REPEATED BELOW. THIS PROGRAM CAN STORE 7 CHANNELS OF TELEMETRY OVER A PERIOD OF UP TO 100 MINUTES (OR 1 CHANNEL FOR APPROX. 700 MINUTES) FOR LATER TRANSMISSION. PLOTS OF THE TELEMETRY CHANNELS RECORDED BY THE SPACECRAFT THROUGHOUT A WHOLE ORBIT (INCLUDING ECLIPSE, ETC) ARE USEFUL INDICATORS TO THE CONDITION OF THE VARIOUS INTERNAL SYSTEMS. THE PROGRAM PRODUCES CHECKSUMMED LINES OF DATA, WITH SERIAL NUMBERS AND A VARIABLE NUMBER OF TELEMETRY DATA VALUES. EACH LINE HAS BEEN RECORDED FROM THE STANDARD TELEMETRY FRAME (5.28 SECONDS DURATION, EACH CHANNEL DIGITISED AT THE TIME IT WOULD BE TRANSMITTED IN THE STANDARD TELEMETRY FORMAT). THE DOWNLINK FORMAT IS: NNNNXYZXYZXYZXYZCC WHERE NNNN IS 4-HEX DIGIT SERIAL NUMBER ( UP TO 046DH LINES ARE SENT AS DATA IS ACCUMULATED ) XYZ ARE BCD TELEMETRY CHANNEL VALUES AS IN ORDINARY TELEMETRY CC IS 1 BYTE CHECKSUM ( ADD NN, NN, 0X, YZ, CC BYTES USING 8-BIT BINARY ADDITION - RESULT SHOULD BE 0AAH ). NNNN=0000 GIVES CHANNEL NUMBERS RECORDED IN 0YZ POSITIONS. THE LINE WITH SERIAL NUMBER 0001 WAS RECORDED AT THE PROGRAM LOAD TIME. NO COMPUTER-READABLE TIMESTAMP IS AVAILABLE, BUT WE WILL ATTEMPT TO GIVE THE PROGRAM LOAD TIME AND TELEMETRY CHANNEL NUMBERS IN FUTURE BULLETINS. DISPLAYING WHOLE-ORBIT DATA IN REAL TIME (OR FROM A TAPE RECORDING) IS AN IDEAL DEMONSTRATION FOR EXHIBITIONS, ETC. ** S/C OPERATIONS SCHEDULE ** FRI 03/6/83 TO MON 06/6/83 1200 TELEMETRY, 1200 BULLETIN, DIGITALKER, 2.4GHZ BEACON MON 06/6/83 TO FRI 10/6/83 VARIOUS DATA FORMATS (145 & 435 MHZ) TO FURTHER INVESTIGATE THE BOOM SITUATION. AN 1802 PROGRAM TO STORE AND RE-TRANSMIT RADIATION COUNTER DATA TOGETHER WITH THE TELEMETRY CHANNELS NECESSARY TO ANALYSE THE SPACECRAFT ATTITUDE HAS BEEN DEVELOPED - TESTING HAS BEEN DELAYED BUT SHOULD BE DONE NEXT WEEK. DOWNLINK FORMAT WILL BE SIMILAR TO THE WHOLE-ORBIT TELEMETRY DATA AND WILL BE DESCRIBED FULLY WHEN TESTING IS COMPLETE ** THANKS FOR REPORTS ** WB8OTH, K1KSY, JA2GSD, B.LINDHOLM, K2AR, K1KSY, ON6UG, KA9Q, F1GRR, G3UMF, JA7IEL, JA7IE WE WOULD APPRECIATE REPORTS FROM STATIONS ABLE TO DECODE DATA FROM THE 435MHZ AND 2.4GHZ BEACONS - RELIABILITY AND BURST LENGTH AT CURRENT ATTITUDE & SPIN - THIS INFORMATION FOR FUTURE PACKET DEMONSTRATIONS. *** UOSAT MISSION PLANNING *** A UOSAT MISSION PLANNING MEETING WAS HELD AT SURREY ON 23/05/83 TO FORMULATE A FORWARD-LOOK FOR THE NEXT THREE MONTH PERIOD OF UOSAT OPERATIONS. THE PLAN REPRESENTS THE OVERALL MISSION DIRECTION RATHER THAN A SPECIFIC OPERATIONS SCHEDULE AND REMAINS FLEXIBLE TO OPERATIONAL EVOLUTION. * STABILISATION/ATTITUDE CONTROL: DETAILED ANALYSIS OF SPACECRAFT DATA HAS LOCATED THE POSITION OF THE TIP-MASS AND BOOM FOLLOWING DEPLOYMENT AND SUBSEQUENT CABLE SNAG. ATTEMPTS TO STRAIGHTEN THE BOOM WILL RESUME, BUT IF UNSUCCESSFUL OR WITHOUT SPECIFIC PROMISE AFTER 10/06/83, ATTEMPTS WILL BE TERMINATED AND NO FURTHER SPACECRAFT TIME ALLOCATED TO THIS PROGRAMME. THE BOOM PROBLEM DOES NOT AFFECT THE USER SPACECRAFT OPERATIONS DRAMATICALLY AND THE FINITE SPACECRAFT RESOURCES SHOULD BE DIRECTED TO OTHER PROFITABLE EXPERIMENTS NOT YET FULLY EXPLOITED. THE SPACECRAFT CAN BE ALLOWED TO REMAIN IN A NATURAL SPIN STATE WHICH IS QUITE ACCEPTABLE, WHILST THE POSSIBILITIES (& DESIRABILITY) OF CONTROLLED SPIN OR WEAK GRAVITY CAPTURE ARE ASSESSED. * H.F.BEACONS EXPT: FOLLOWING THE TERMINATION OF THE STABILISATION PROGRAMME, THE H.F. ANTENNAS WILL BE DEPLOYED AND THE BEACONS ACTIVATED. * PARTICLE EXPERIMENT: ADVANCED SOFTWARE HAS BEEN RECENTLY DEVELOPED TO ENHANCE THE VALUE OF THE EXPERIMENT DATA. WHEN COMMISSIONED, THE NUMBER OF WHOLE ORBIT OBSERVATIONS WILL BE INCREASED. * 2.4GHZ BEACON: THE BEACON HAS BEEN ACTIVATED RECENTLY AND SUCCESSFULLY RECEIVED IN THE UK AND BELGIUM. THIS BEACON CARRIES THE SAME DATA AS THE 145MHZ DOWNLINK, AND WILL BE ACTIVATED ROUTINELY AT WEEKENDS, POWER BUDGET PERMITTING, AND FOR OTHER SPECIFIC EXPERIMENTS. * CCD CAMERA & VIDEO EXPT: THE OPERATIONAL IMPLICATIONS OF CLOSING THE LINK BETWEEN THE 1802 COMPUTER AND THE VIDEO DISPLAY EXPT. WILL BE ANALYSED IN DETAIL WITH A VIEW TO POSSIBLE IMAGE PROCESSING OF THE CCD DATA AND, PARTICULARLY, UP-LOADING IMAGES AND GRAPHICS FROM THE GROUND. (IN ADDITION, THIS LINK PROVIDES ACCESS TO A FURTHER 32K OF MEMORY FOR THE 1802 FOR USE IN DATA COLLECTION AND BULLETINS ETC.) THIS ACTIVITY IS HIGHLY DESIRABLE TO STIMULATE INTEREST IN THE CCD & VIDEO EXPERIMENTS AND TO EVALUATE THE SYSTEM FOR FUTURE SPACECRAFT EXPERIMENTS. * DIGITALKER: THE DIGITALKER EXPT. HAS BEEN HIGHLY SUCCESSFUL AND GENERATED A GREAT DEAL OF INTEREST WHILST, AT TIMES, PROVING OPERATIONALLY VALUABLE. EFFORTS WILL BE MADE TO EXPAND THE SCOPE OF THIS EXPT. * SCIENTIFIC MAGNETOMETER: THIS INSTRUMENT HAS, THUS FAR, BEEN UTILISED PRIMARILY FOR SPACECRAFT NAVIGATION HOWEVER IT IS PROPOSED TO DEVELOP SOFTWARE TO ALLOW THE STUDY OF THE SHORT-TERM, LOW-LEVEL PERTURBATIONS TO THE GEOMAGNETIC FIELD AND THEIR RELATIONSHIP TO RADIOWAVE PROPAGATION PHENOMENA. * DIGITAL PACKET RADIO COMMUNICATIONS: IN PREPARATION FOR THE PROPOSED PACSAT SPACECRAFT, PACKET RADIO EXPERIMENTS SHOULD BE INITIATED BETWEEN UOS AND AMSAT-USA DEVELOPING FURTHER THE EXISTING PACKET COMMUNICATIONS USED IN THE CONTROL AND DATA TRANSFER ON UOSAT. *SPACECRAFT ORBITAL DATA* ORBITS FOR 3RD JUNE UOSAT OSCAR-8 NOAA-7 ORBIT NO : 9171 26733 10026 EQX TIME : 14:23:43 14:08:00 14:12:07 GMT EQX LONG : 346.9 292.6 347.5 DEG.W MEAN HGT : 502.6 904.0 850.0 KM PERIOD : 94.6665898 103.1663189 101.9030050 MINS P-DRAG : 5.194E-05 8.277E-07 7.500E-06 *N-REF LONG INC : 23.6657635 25.7899720 25.4879948 DEGS L-DRAG : 1.307E-05 .000E+00 2.000E-07 *N-REF RECEPTION REPORTS AND UOSAT DATA IS MUCH APPRECIATED SEND TO: UOSAT TEAM, UNIVERSITY OF SURREY, GUILDFORD, SURREY, ENGLAND - THANK YOU