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