SWSU-55 satellites – determination of the spin rate

I am currently working on determining the spin rate of the SWSU-55 satellites. You see from most SSTV images that all SWSU-55 satellites spinning very fast.
Now we are lucky and can read the angular velocity (xyz axis) from the beacon. This shows that the satellite is rotating in all 3 axes, i.e. it is tumbling.
If you look at the field strength, you can see a period of 4.5 sec. I assume that this is one rotation. This results in a value of 13.3 rpm.


Based on the SSTV image you can also see 8 noise dips (lines) within the 36 seconds.

The angular velocity can be computed as w = sqrt(Vx^2 + Vy^2 + Vz^2) and the rotation axis can be computed as the unit vector (Vx, Vy, Vz)/w.

So we see similar rotation values. This is what we get from the gyros, and also from the fades in the signal power and SSTV image. Based on the radiation pattern of a dipole I assume the assignment to the axis as shown in my drawing below.

… and we still observe the Dzhanibekov effect, also called the intermediate axis theorem or tennis racket theorem describes the behaviour of a rigid body with three distinct principal moments of inertia.

13:08:39 RS5S>ALL>UI,C,F0 (1124 baud):
SWSU-55 #7 S=290 U1=4.51 U2=4.37 T1=12.72 Mx=9.643372 My=32.069817 Mz=-48.665386 Vx=-38.816795 Vy=56.412212 Vz=45.847328 Time=1080475103 R
13:09:18 RS5S>ALL>UI,C,F0 (1124 baud):
SWSU-55 #7 S=291 U1=4.48 U2=4.45 T1=13.04 Mx=-16.819834 My=4.709554 Mz=-3.812496 Vx=-48.839695 Vy=-9.167939 Vz=70.931297 Time=1080510009 R
13:12:40 RS5S>ALL>UI,C,F0 (1127 baud):
SWSU-55 #7 S=294 U1=4.43 U2=4.28 T1=14.01 Mx=7.400727 My=-52.253620 Mz=-47.319801 Vx=-48.114502 Vy=6.099236 Vz=-69.580154 Time=1080625225 R
14:42:50 RS5S>ALL>UI,C,F0 (1124 baud):
SWSU-55 #7 S=391 U1=5.00 U2=4.98 T1=12.72 Mx=25.117619 My=42.161720 Mz=34.536728 Vx=-52.977100 Vy=51.541985 Vz=-45.351147 Time=1085566194 R
14:46:13 RS5S>ALL>UI,C,F0 (1125 baud):
SWSU-55 #7 S=394 U1=4.48 U2=4.46 T1=13.37 Mx=-16.595570 My=4.036760 Mz=11.213223 Vx=-45.190838 Vy=-70.725189 Vz=-12.167939 Time=1085680123 R
14:51:34 RS5S>ALL>UI,C,F0 (1126 baud):

Update SWSU-55 – telemetry

RS9S>ALL>UI,C,F0:
KETs #1 S=2765 U1=4.80 U2=4.77 T1=13.37 Mx=26.687471 My=4.261025 Mz=52.253620 Vx=-26.839695 Vy=-79.022903 Vz=-57.854961 Time=1028440205 R1=0 R2=0
RS9S>ALL>UI,C,F0:
KETs #1 S=2771 U1=4.93 U2=4.89 T1=14.98 Mx=24.220562 My=13.007339 Mz=76.698448 Vx=25.015266 Vy=-82.198471 Vz=-45.748093 Time=1028683140 R1=0 R2=0
RS9S>ALL>UI,C,F0:
KETs #1 S=2774 U1=4.73 U2=4.70 T1=15.62 Mx=23.547768 My=92.172691 Mz=54.944794 Vx=-17.129770 Vy=-79.206108 Vz=-59.541985 Time=1028790042 R1=0 R2=0
RS9S>ALL>UI,C,F0:
KETs #1 S=2775 U1=4.94 U2=4.91 T1=15.62 Mx=44.628628 My=69.297714 Mz=84.099174 Vx=21.183207 Vy=-81.603050 Vz=-48.900764 Time=1028861142 R1=0 R2=0
RS9S>ALL>UI,C,F0:
KETs #1 S=2776 U1=4.98 U2=4.94 T1=16.27 Mx=48.665386 My=44.180099 Mz=-7.849256 Vx=-70.297707 Vy=-71.038170 Vz=17.580153 Time=1028893012 R1=0 R2=0

RS5S>ALL>UI,C,F0 (1126 baud):
SWSU-55 #7 S=8895 U1=4.51 U2=4.36 T1=14.98 Mx=43.058777 My=-40.816132 Mz=-39.919075 Vx=-43.366413 Vy=24.473282 Vz=-61.923664 Time=1005463036 R
RS5S>ALL>UI,C,F0 (1127 baud):
SWSU-55 #7 S=8896 U1=4.77 U2=4.76 T1=14.98 Mx=78.492561 My=4.036760 Mz=-20.632330 Vx=-31.969465 Vy=-62.847328 Vz=-30.374046 Time=1005502031 R

RS4S>ALL>UI,C,F0 (1142 baud):
SWSU-55 #6 S=1931 U1=4.73 U2=4.70 I1=0.0 T1=22.71 Mx=0.672793 My=86.790344 Mz=9.194843 Vx=0.000000 Vy=0.000000 Vz=0.000000 Time=974092004
RS4S>ALL>UI,C,F0 (1142 baud):
SWSU-55 #6 S=1934 U1=4.42 U2=4.31 I1=0.0 T1=23.04 Mx=-18.613951 My=83.202118 Mz=9.643372 Vx=0.000000 Vy=0.000000 Vz=0.000000 Time=974197224
RS4S>ALL>UI,C,F0 (1143 baud):
SWSU-55 #6 S=1940 U1=4.78 U2=4.75 I1=0.0 T1=25.29 Mx=-5.606611 My=30.724232 Mz=60.775669 Vx=0.000000 Vy=0.000000 Vz=0.000000 Time=974471104
RS4S>ALL>UI,C,F0 (1142 baud):
SWSU-55 #6 S=1941 U1=4.72 U2=4.69 I1=0.0 T1=25.29 Mx=51.356560 My=39.246281 Mz=23.099239 Vx=0.000000 Vy=0.000000 Vz=0.000000 Time=974504127

Meaning of the telemetry channels

S - the number of the packet from the moment the telemetry is turned on or reset
U1 - solar cell voltage V
U2 - battery voltage V
I2 - total current mA
T1 - processor temperature ะก
M# - magnetic field strength micro Tesla three axes xyz
V# - angular velocity deg/sec three axes xyz
Time - the time since the telemetry was turned on or reset in ms

R1 and R2 (only on KETs) – power of calibration transmitters in dBm


SSTV picture sent from RS5S


RS5S and RS6S send the same children’s drawings (shuffled)

SWSU-55 #8 – RS6S SSTV and telemetry

13:15:09 RS6S>ALL>UI,C,F0 (1134 baud):
SWSU-55 #8 S=5984 U1=4.84 U2=4.83 T1=18.52 Mx=47.319801 My=17.716892 Mz=46.422745 Vx=-8.740458 Vy=-81.725189 Vz=-26.122137 Time=802336055
13:21:19 RS6S>ALL>UI,C,F0 (1135 baud):
SWSU-55 #8 S=5989 U1=4.82 U2=4.80 T1=20.78 Mx=64.812431 My=16.371305 Mz=-26.687471 Vx=-9.679389 Vy=-81.946564 Vz=-36.007633 Time=802588224
13:22:32 RS6S>ALL>UI,C,F0 (1135 baud):
SWSU-55 #8 S=5991 U1=4.81 U2=4.79 T1=21.42 Mx=84.996231 My=30.275702 Mz=71.540359 Vx=-16.885496 Vy=-82.175575 Vz=-29.687023 Time=802727002

Update SWSU-55 – SSTV and NORAD ID’s

437.0000 MHz - SWSU-55 No8 - RS6S #53311
437.0125 MHz - Tsiolkovsky-Ryazan 2 - RS12S #53313
437.0250 MHz - Tsiolkovsky-Ryazan 1 - RS9S #53312
437.0500 MHz - SWSU-55 No1 & R-390 - RS10S ** not active
437.0620 MHz - SWSU-55 No2 - RS11S ** not active
437.0750 MHz - SWSU-55 No3 - RS1S #53309 ** not active anymore (carrier)
437.0820 MHz - SWSU-55 No4 - RS2S ** not active
437.0870 MHz - SWSU-55 No6 - RS4S #53306
437.1000 MHz - SWSU-55 No5 - RS3S #53308
437.1125 MHz - SWSU-55 No7 & R-390 - RS5S #53310

thanks, Nico PA0DLO for assignment

Every day new SSTV pictures are added to my collection, but the quality is decreasing rapidly. All satellites seem to rotate faster and faster. I don’t know with which system they are stabilized (possibly only a permanent magnet) – but the spin rate increases daily. That is a pity.

Sometimes only a carrier can be seen without modulation. This is normal, the KETs send a carrier to tune the space telescope on the ground. RS1S, on the other hand, seems no longer to work (continuous carrier).

SWSU-55 telemetry packets and new SSTV images

Based on the quality of the SSTV images, the SWSU-55s are spinning faster and faster rather than settling down …

telemetry on 437.05 MHz:
18:52 RS4S>ALL>UI,C,F0 (1142 baud):
SWSU-55 #6 S=8573 U1=4.88 U2=4.85 I1=0.0 T1=22.39 Mx=14.577189 My=82.305054 Mz=-13.680132 Vx=0.000000 Vy=0.000000 Vz=0.000000 Time=385422154
20:29 RS9S>ALL>UI,C,F0 (1136 baud):
KETs #1 S=9107 U1=4.91 U2=4.88 T1=23.04 Mx=32.294083 My=73.110214 Mz=84.323441 Vx=39.564884 Vy=-103.106873 Vz=6.167939 Time=415360187 R1=0 R2=0
20:31 RS5S>ALL>UI,C,F0 (1129 baud):
SWSU-55 #7 S=7652 U1=5.01 U2=4.99 T1=16.27 Mx=70.643303 My=38.797752 Mz=4.709554 Vx=40.717556 Vy=-21.977098 Vz=-44.954197 Time=403688156 R
20:47 RS1S>ALL>UI,C,F0 (1142 baud):
SWSU-55 #3 S=2906 U1=4.92 U2=4.89 I1=0.0 T1=23.36 Mx=-23.099239 My=-34.312462 Mz=124.915306 Vx=18.213741 Vy=75.473282 Vz=35.893131 Time=118567254
20:47 RS3S>ALL>UI,C,F0 (1157 baud):
SWSU-55 #5 S=8674 U1=4.84 U2=4.83 I1=0.0 T1=22.07 Mx=60.551403 My=-3.139702 Mz=-19.286743 Vx=-40.526718 Vy=36.870228 Vz=14.748092 Time=394387113

SWSU-55 spectrum – active satellites

437.050 MHz 1k2 AFSK Telemetry - all

Payload: DATA, SSTV, VOICE
---------------------------
437.0000 MHz - SWSU-55 No8 - RS6S active
437.0125 MHz - Tsiolkovsky-Ryazan 2 - RS12S active
437.0250 MHz - Tsiolkovsky-Ryazan 1 - RS9S active
437.0500 MHz - SWSU-55 No1 & R-390 - RS10S not active
437.0620 MHz - SWSU-55 No2 - RS11S not active
437.0750 MHz - SWSU-55 No3 - RS1S active
437.0820 MHz - SWSU-55 No4 - RS2S not active
437.0870 MHz - SWSU-55 No6 - RS4S active
437.1000 MHz - SWSU-55 No5 - RS3S active
437.1125 MHz - SWSU-55 No7 & R-390 - RS5S active