AO51 magnetic 'flip' experiment successful

Since its launch, AMSAT-Echo AO-51 has carried a spacecraft attitude adjustment experiment which was tested for the first time this week.

The experiment contains a 'reversible' magnet which will align the spacecraft with Earth's magnetic field.

On the December 2, 2242 UTC pass of AO-51 AMSAT-NA VP Operations Drew Glasbrenner, KO4MA issued the command to reverse the magnet and "flip" the orientation of the satellite.

The first effect of the experiment was expected to be some changes in signal levels and patterns. AO-51's 435 MHz downlink was expected to become slightly weaker in the northern hemisphere and slightly stronger in the south-
ern hemisphere.

ZL2BX reported, "With two usable passes over ZL last night the most notable feature was the frequent polarity shifts. Certainly good strong signals but difficult to tell how it compares to previous signal levels."

IW4DVZ reported results from a contact with EI8JB, "For me nothing changed, I received from AO-51 the same strong signal as usual."

W6ZKH reported the only difference were frequent polarity changes. The signal strength here on the West Coast seemed to be the same as before.

Tom Clark, K3IO offered an explanation for the received signal changes, "Since angular momentum must be conserved when you "flip" the spacecraft it should precess (probably looking like tumbling) until the momentum dampers absorb the change. Keep an eye on the solar panel currents and I'll bet the spin rate will change."

Drew concluded, "We are still sifting through the telemetry, but as Tom suggested in his email, the satellite is precessing (wobbling) quite severely. This will calm down as the hysteresis rods do their job.

Initial reports from Australia and New Zealand indicate stronger signals, and about the same from South Africa. There are some peculiar things about the magnetic field near South Africa, so that doesn't surprise me too much, but is worth digging into once we get the whole orbit telemetry down."

The AO-51 Command Team appreciates any signal reports or observations for the next few days that you can email to ao51-modes@amsat.org or ko4ma@amsat.org. In a week or so the Command Team expects to re-orient AO-51 back to its original attitude.

Twitter users can receive tweets from the AO-51 command team at http://twitter.com/AMSAT or by adding "AMSAT" to your follow list.

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