karn@mouton.UUCP (07/26/84)
**** UoSAT Bulletin-83/84 20th July 1984 ****
** UoSAT-OSCAR-9 Status **
Following problems encountered loading the bootstrap loader
last Friday (the 13th!), Oscar-9 was left generating an
all-too-familiar tone as the corrupted loader branched around
its checksumming routine, turned the 145MHz beacon on and then
promptly crashed! Valiant efforts - including the modification
and use of Oscar-11 command equipment - were made at Guildford
to remedy the problem using the 438MHz uplink, but due to a
design feature, this uplink is dependent on the 144MHz squelch,
which frequently stays open for prolonged periods. Persistence
paid off, however, and the beacon was finally turned off on
Thursday 19/7/84. Normal service according to the schedule
below will hopefully be restored.
** UoSAT-OSCAR-11 Status **
This report combines the news from the past fortnight's
operations...
The past fortnight has primarily been one of consolidation
prior to boom deployment operations, expected within the next
two or three weeks. The opportunity has been taken to test a
number of the other experiments on the spacecraft, although
most of these will not be operated further until the craft is
locked pointing downwards. Much more analysis of the
spacecraft's attitude both now and after gravity-gradient boom
deployment has been performed, and software to run in real time
on the ground-station computers has been written and tested.
The pyrotechnic bolt-cutters securing the boom tip-mass to the
top of the spacecraft were fired on orbit 1909.
A daily account follows:
Friday 6/7/84
Monitored the TORQUEC automatic magnetorquing program and
collected more data in dwell mode to analyse.
Saturday 7/7/84
More monitoring
Sunday 8/7/84
Yet more monitoring
Monday 9/7/84
Loaded the ODATA whole-orbit telemetry recording program at
20:21:46, recording channels 1,2,3,10,50,52. Analysis shows
that the spacecraft remains adequately 'locked' to the earth's
magnetic field for only about 15-20 minutes after the automatic
magnetorquing program is turned off - this affects our planning
for boom deployment. Automatic magnetorquing was re-enabled on
next pass.
Tuesday 10/7/84
The boom tip-mass release pyrotechnics were fired on orbit
1909.
During the evening, a new version of TORQUEC with an
interruption facility was tested. This allows updates to the
magnetorquer firing parameters to be loaded without re-loading
the whole program. The test was successful.
Wednesday 11/7/84
ODATA was run at 18:25:34 to look at the temperatures of the
top and bottom panels of the spacecraft as an independent
measurement of attitude. The channels monitored were
1,2,3,19,29,59. Again, TORQUEC was re-loaded on the subsequent
pass.
Thursday 12/7/84
TORQUED was loaded and tested successfully. This program
contains an additional loop which allows a sequence of commands
to be uploaded and sent to the telecommand system at
pre-determined intervals. This will allow us to deploy the
boom under automatic control, possibly allowing the operation
to be performed elsewhere than over England. This will allow
more flexibility in the boom deployment planning.
Friday 13/7/84
The Digital Store and Readout experiment was powered up on
orbit 1958, and data from the 1802 computer UART was recorded
and re-played successfully. Apart from the serial input, the
DSR also has very fast parallel inputs from the CCD camera and
the Radiation experiments and is the only device which can
store the data from these (at least in the short term). The
DSR features an extremely sophisticated readout mechanism,
complete with synchronisation characters, a Hamming-encoded
memory address, data protected by a CRC code and the whole
block enclosed in a Fire code for burst error correction. A
datasheet explaining these is under preparation, but the
initial checking of the downlink data received is taking lower
priority than many other current activities.
Also on Friday 13/7/84, the 435MHz beacon was tested briefly,
and found to be working well. Due to the initial command
problems, this beacon will not be activated again until after
g-g stabilisation, when the effects of blocking the 438MHz
uplink will be measured.
Saturday 14/7/84
TORQUEE - the latest of the automated magnetorquing programs -
was loaded and run. This program has the added feature of
concurrent ODATA storage and playback, so that the effect of
magnetorquing over the whole orbit can be evaluated without
interrupting it. After an orbit with a decoy checksum, the
first successful run was on orbit 1973, recording channels
1,2,3,10,50,52.
Also on orbit 1973, the 2.4GHz beacon was powered up for the
first time. This beacon also performed well, and was used a
few times over the weekend. It is hoped, after more checks of
possible effects on the uplinks, to be able to leave this
beacon powered for longer periods when the power budget allows.
Sunday 15/7/84
TORQUEG was tested. This version allows the ODATA recording to
be reset by ground command, preventing the program from having
to be re-loaded. This worked well. The ODATA was reset after
various tests at 21:03:10, this time displaying channels
1,2,3,35,50,52.
Monday 16/7/84
Further ODATA resets (using channels 1,2,3,35,50,52) were done
at 08:48:25 and 11:59:50 as 2.4GHz tests continued.
TORQUEH - outputting ODATA with non-sequential channel numbers
- was run during the evening - details of timing unavailable.
The evening was also spent testing the Radiation detectors, but
this was not particularly successful - as expected - because
they draw more current than the supply trips allow at this
temperature. More tests will be done after stabilisation is
complete.
Tuesday 17/7/84
The CCD camera, dumping to the DSR, was tested for the first
time. After a few false starts configuring the memories, a
test image was taken. Analysis of the DSR downlink format and
development of the decoder and display are in progress, but the
initial results look promising.
Wednesday 18/7/84
This was spent running some uplink and receiver tests.
Thursday 19/7/84
The ODATA section of TORQUEH was reset at 09:02:14, which
highlighted a problem in the program. The program was re-run
around 12:20, but the reason for the earlier problem is not yet
fully known. The program was again reset at 20:13:45, to
channels 1,2,3,35,50,52.
** UoSAT-OSCAR-11 Operations Schedule **
We will be using dwell telemetry, with channels 01, 02, 03, 61
and 67 transmitted in a one-line frame with the standard
checksum, thus providing very fast data for ground analysis.
(Note channel 67 has been added to monitor the computer
command. The MSB of channel 67 is the magnetorquer demand flag
(set when commands sent if they are enabled), the other 3 bits
in the first digit giving type of firing (based on a z-field
change or a transverse field change) and the bottom 8 bits
giving a measure of the transverse change.)
** UoSAT-Oscar-9 Schedule **
The 2.4GHz beacon will be in use this weekend.
Friday Load bulletin
Saturday Bulletin / 1200 bd telemetry / Digitalker
Sunday Bulletin / 1200 bd telemetry / Digitalker
Monday Whole-orbit radiation data
Tuesday Checksummed telemetry
Wednesday CCD image
Thursday Whole-orbit telemetry data
Friday Load bulletin
Based on the response to our questionnaire, we are considering
generating Digitalker for the educational 'market' on Mondays,
now that we have started transmitting CCD images on Wednesdays.
Radiation data will be scheduled occasionally.
** UoSAT-Oscar-9 bulletin #82 **
Last week's bulletin filled the memory of the 1802 computer
leaving only 3 bytes spare! More notably, a new cross
assembler written by G8NEF made it possible to alter the
bulletin slightly, compile it, load 16kb onto the spacecraft
and run it all during a 32 degree elevation pass, lasting some
12 minutes. The compilation time of around 30 seconds compares
very favourably with the 20 or 25 minutes typically taken with
the previous facility. The assembler also features UoSAT
checksum generation and loader support routines.
** General News - UoSAT Newsletters **
The following information has finally been printed at UoS. The
full pack will be sent to all enquirers who have written to us
since February this year, just ask for individual sheets if you
want them!
Newsletter - General status of UoSAT activities at June 1984
Datasheet 1 - UoSAT Project Summary
Datasheet 2 - UoSAT-1 Technical Data Summary
Datasheet 3 - UoSAT-1 Orbit Geometry, Tracking and
Groundstation details
Datasheet 4 - UoSAT-1 Telemetry
Datasheet 5 - UoSAT-2 Project Summary
Datasheet 6 - UoSAT-2 Technical Description
Datasheet 7 - UoSAT-2 Reception, Data formats
and Telemetry equations
Datasheet 8 - UoSAT-2 FSK demodulation using BBC Micro.
Questionnaire - As transmitted on this bulletin
Sheets describing the DSR data format and how to assemble this
data to make up CCD images are under preparation as time
allows.
** Weather Satellite Status **
* The NOAA-8 spacecraft is being decommissioned following a
failure of the primary oscillator which commands the timing of
the gyros and attitude control system. Engineers have not been
able to switch over to the redundant oscillator as the primary
oscillator has not yet failed completely.
* The NOAA-6 spacecraft has been re-activated to replace the
failed NOAA-8 data.
* NOAA-7 will complete its planned operational lifetime this
summer, but is continuing to perform well.
* The NOAA-9 spacecraft is currently scheduled for launch on 23
October 1984.
* METEOR-2-7 remains active on 137.3 MHz
* METEOR-2-9 has not been heard recently.
* METEOR-2-8 is now active on 137.85 MHz.
** Thanks for Reports & Questionnaire Returns **
ZL1MO, G6AAL, IV3TKI, ZL1AOX, G3WDI / Kessingland VCP School,
G4BZB, OZ1RO, HB9AYX, K1KSY, Sir William Turner's 6th Form
College, G3TKW, G3UVC / Southampton C.H.E., Birger Lindholm.
OZ1WN, G3FIJ, ON1BTH, JA2WO.
This week: HB9RJV / HB9RKR, PY2NKW, KDX1A, G3VOM, DD2OJ /
DB2OS.
** Keplerian Orbital Elements - from KA9Q **
Satellite: oscar-9
Catalog number: 12888
Epoch time: 84188.40501187
Fri Jul 6 09:43:13.25 1984 UTC
Element set: 660
Inclination: 97.5947 deg
RA of node: 163.2729 deg
Eccentricity: 0.0004512
Arg of perigee: 57.4152 deg
Mean anomaly: 302.7513 deg
Mean motion: 15.26041520 rev/day
Decay rate: 2.864e-05 rev/day^2
Epoch rev: 15247
Semi major axis: 6862.762 km
Anom period: 94.361784 min
Apogee: 502.631 km
Perigee: 496.438 km
Ref perigee: 2378.41543257
Fri Jul 6 09:58:13.373 1984 UTC
Beacon: 145.8250 mhz
Satellite: oscar-10
Catalog number: 14129
Epoch time: 84177.96936827
Mon Jun 25 23:15:53.418 1984 UTC
Element set: 107
Inclination: 25.5969 deg
RA of node: 192.2384 deg
Eccentricity: 0.6084343
Arg of perigee: 283.3262 deg
Mean anomaly: 18.9696 deg
Mean motion: 2.05846041 rev/day
Decay rate: 2e-07 rev/day^2
Epoch rev: 779
Semi major axis: 26106.433 km
Anom period: 699.551953 min
Apogee: 35616.117 km
Perigee: 3848.018 km
Ref perigee: 2367.94376985
Mon Jun 25 22:39:01.715 1984 UTC
Beacon: 145.8100 mhz
Satellite: oscar-11
Catalog number: 14781
Epoch time: 84182.80563673
Sat Jun 30 19:20:07.13 1984 UTC
Element set: 33
Inclination: 98.2397 deg
RA of node: 244.9611 deg
Eccentricity: 0.0012098
Arg of perigee: 246.8929 deg
Mean anomaly: 113.1014 deg
Mean motion: 14.61880279 rev/day
Decay rate: 1.45e-06 rev/day^2
Epoch rev: 1769
Semi major axis: 7062.326 km
Anom period: 98.503278 min
Apogee: 710.445 km
Perigee: 693.357 km
Ref perigee: 2372.78414588
Sat Jun 30 18:49:10.203 1984 UTC
Beacon: 145.8260 mhz
** Spacecraft orbital data **
Orbits for 20th July
UoSAT UoSAT-2 NOAA-8
Orbit no : 15462 2057 6823
Eqx time : 15:11:20 14:04:24 14:16:37 GMT
Eqx long : 348.1 244.6 287.8 deg.w
Mean hgt : 490.9 689.9 850.0 km
Period : 94.4043523 98.5601585 101.2702550 mins
P-drag : 4.318E-05 2.914E-06 9.000E-06 *N-ref
Long inc : 23.5991958 24.6391120 25.3298590 degs
L-drag : 1.086E-05 7.331E-07 2.000E-07 *N-ref
Incl : 97.590 98.242 98.900 degs
Freq : 145.825 145.825 137.500 MHz
Larry,
** UOSAT-OSCAR-11 Gravity Gradient Boom Deployment **
Following several days final preparation and rehearsals,
the UO-11 gravity gradient boom was deployed under on-board
computer (OBC) control at 10:35 gmt today 24 July on orbit
2113.
The automatic magnetorquing manoeuvres continuously
executed by the OBC over the last few weeks, had aligned the
spacec closely to the geomagnetic field vector and reduced
residual motions (wobble) to a very low value. Following final
confirmation at AOS at Surrey on orbit 2113, the OBC was given
instructions to terminate the magnetorquing routines and
deploy the boom for 15 minutes taking the spacecraft out of
range of UoS. Spacecraft telemetry indicated reasonable boom
motor current and correct operation of the OBC. The OBC
recorded X,Y,Z, +5V current and boom & computer status
channels automatically throughout the following orbit, whilst
the boom was being deployed, to monitor gravity gradient
capture.
The stored data was dumped at UoS on the next orbit (2114)
and confirmed the correct operation of the OBC routines and
preliminary analysis of the stored Navigation Magnetometer
data indicates successful gravity gradient capture.
**NOTE**
Gravity capture may occur successfully WITHOUT correct boom
extension due to the excellent initial attitude of the
spacecraft reliant solely on the asymmetric body shape -
residual energy and the effect of perturbing forces, however,
are likely to cause this condition to deteriorate quite
rapidly if the boom has not deployed to a significant extent.
Data gathered over the next day or so will confirm
successful (or otherwise) gravity gradient stabilisation and
will indicate the degree of libration.
The most obvious effect of gravity gradient capture is that
the spacecraft will now make only one rotation around the
earth - rather than two when magnetiacally stabilised.
Residual energy before boom deployment will translate itself
into subsequent libration after GG-lock.
More news will be forthcoming as we have it!!
Martin, Neville, Roger, Stephen + UO-11!
END