Luister na OBC1 se klingel, OBC2 se boodskap, die 1200 en 9600 baud modems of die eerste herhaler-kontak met Sunsat (tussen Stellenbosch en Durban).
If you have a good link you can download a the movie file showing the
release and detumbling of Sunsat (7.7MByte): Sunsat Movie
(streaming RealVideo)
22 March 1999
A inorbit roll maneuver is executed using the Z axis reaction wheel. The
maneuver rotates the satellite through 180 degrees. On the graph the up
and down ramping of the reaction wheel is visible. The rough sun sensors
indicate the rotation of the satellite. Initially the -Y side was pointing
towards the sun. During the manuever the -Y side moved away from the sun,
the -X side moved into and then away from the sun and finally the +Y side
moved into the sun.
21 March 1999
Early Sunday morning the Y axis reaction wheel is switched on to perform
a yaw maneuver. From the downloaded data the maneuver appears to
be a complete success. Later the day Sunsat's radios are enabled to act
as a radio transponder for radio amateurs in South Africa. They spend an
enjoyable 10 minutes talking to each other through Sunsat. 32 call signs
are identified during the transmission from all over South Africa.
16 March 1999
At 01:46 UTC the second onboard computer on Sunsat was booted and it transmitted
a message back indicating that it is working as expected. Listen
to the start of the message
14 March 1999
The radio amateur transponder is enabled for a short test period using
a VHF uplink and UHF downlink. During this time the first radio contact
was established between Stellenbosch ground station and a radio amateur
in Kwazulu Natal while using Sunsat as a relay station.
11 March 1999
The S-Band high speed data link was switched on at 01:46 UTC and the first
s band signal is acquired on the dish antenna at Stellenbosch at 13:55
UTC.
7 March 1999
The telemetry received over the weekend confirmed that Sunsat is stabilised
earth pointing with a slow z axis spin. The detumbling controller gravity
locked the satellite on Friday. The attached magnetometer data show confirmed
the gravity lock of the satellite. The crude sun sensor data confirmed
that the satellite is earth pointing. The attached solar panel temperature
show the extreme temperature seen by the solar panel as the satellite’s
orbit takes it in and out of the earth’s shade.
3 March 1999
The communication problems with Sunsat seem to be solved. The ground station
has had faultless communications with the satellite for the last 24 hours.
The stabilisation of Sunsat is progressing well. The attitude determination
and control system is using magneto-torquers to stabilise the satellite.
The magneto-torquers produce a torque on the satellite by using the interaction
between the earth’s magnetic field and a magnetic field induced by a coil.
The attached graph show the decrease in spin tempo, as seen from the X
axis magnetometer, during control using the Y axis magneto-torquer.
2 March 1999
Today was a frustrating day in which failures in ground station equipment
hampered progress in the stabilisation of the satellite. No communication
was established during the early morning passes, but after repairs to the
ground station equipment communications was re-established this afternoon.
1 March 1999
The first whole orbit data from the satellite has been downloaded. The
first attach graphs show the calibrated magnetometer data. This has been
processed to determine the spin rates of the satellite. The second the
temperatures measured during a few orbits on the outside of the satellite.
The third show the batteries on the satellite charging and discharging
in orbit. From the data Sunsat appears to be healthy. The team will now
continue stabilising the satellite by testing the stabilisation controllers.
28 February 1999
From telemetry down loaded early this morning it appears that the Sunsat
boom deployment was a complete success. The boom was deployed parallel
to the earth and perpendicular to the orbit, which left Sunsat travelling
on its side. The satellite have started moving to a more upright position
due the difference in inertia around the x,y and z axes. This is expected
to leave the satellite in a very slow head over heel spin (approximately
2 revolutions per minute), which will be dampened using the magneto torquers
on the satellite. The sequence below shows the boom deployment. On the
left is the spinning satellite and on the right the boom during deployment.
The centre picture shows the satellite after the stabilisation.
The satellite appears to be very healthy and the battery temperature dropped
to 16 degrees Celsius. The onboard computer has been running continuously
for more than 24 hours. The computer operated uninterrupted except for
a reset due to memory corruption in the South Atlantic anomaly. The reset
was done by the edac (Error detection and correction) system on the computer.
The onboard computer is currently capturing whole orbit data that will
be used in the stabilisation of the satellite.
27 February 1999
The Sunsat gravity boom was deployed at 02:00 in an effort to remove the
satellite from an unfavourable inertial stable orientation. The unfavourable
position hampered communications and increased the battery temperature
to above 40 degrees Celsius. All initial indications are that the boom
deployed successfully. In two consecutive passes, there was a dramatic
improvement in communications and the battery temperature dropped to 27
degrees.
The Sunsat team will start the earth pointing stabilisation of the satellite
later today and hope to complete it in the two or 3 days. After stabilisation
the commissioning of the scientific and amateur radio payloads will be
done. This is excepted to take at least a month.
26 February 1999
Communication was successfully established again. A big step forward was
the switch-on of the first on board computer OBC1. The "jingle" that OBC1
on-board SUNSAT relayed was "I'm Alive" - Good news indeed!
25 February 1999
Communication with SUNSAT was established and among other data SUNSAT relayed
the temperature of both it's top and bottom plate. Both temperatures were
quite low, which is good for the condition of the batteries.
