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Re: Latest news on AMSAT-DL page



Hi Don,
Once upon a time ...
I was supposed to have learnt German, but was never really good at it,
and have not used it much in 30 years. However, I did pick my way through
the original.
I was too chicken to volunteer a complete translation.
German is very exact and that makes it difficult to translate, certainly a word
by word rendering is as close to Gibberish as anything I can think of.
Here is my kneading of your Babel fish, I hope it has not turned into two
loaves of rye bread ....

73 Jens    ZL2TJT


Three-axis stabilization of Ao-40.
-----------------------------------
With the transition of spinstabilized mode to three-axis stabilized
mode of Ao-40, longer service life would be obtained with improved
Squintangles.
But after the propulsion incident in December 2000 and the consequences
from it, new more complicated basic conditions result. In the following
contribution, the central problems and the further procedure are described
on the basis of summarized information by the project manager Karl Meinzer,
DJ4ZC, and the command team.

After the incident in the drive system and with the lost fuel, several basic
conditions have changed in such a manner that the subject of three-axis
stabilization was to be reconsidered completely again.
To these changes belong:

1. By the inclination of up to 10deg (fig. 1, A) as opposed to the originally
planned approximately 61deg (fig. 1, B), has the geometry between earth,
sun and satellite become different, which makes another strategy in the
present situation necessary.

2. The so-called " Mystery Effect (ME) " makes the movement of the satellite
uncontrollable, if the spin of AO-40 is so far reduced that the three spin
wheels (fig. 2) can take up the remaining angular momentum, without pushing
to their speed limit.

3. Since the omni antennas failed, each larger change of attitude, (ALAT),
leads to the loss of communication (fig. 1, C).

4. The communication in perigee proximity, with bad Squint, permits
practically no real time control of the three-axis automatic control loop in
the satellite.

For a long time the question was simply, whether there is at all a safe way
to be able to reach a three-axis stabilization without then loosing the control
of the satellite and communication.
In the meantime a strategy was developed, by project manager Karl Meinzer,
which permits a return, with some probability, to the spin mode from each
phase of the transition in time.
Thus it is not sure yet whether Ao-40 can be actually transferred into the
three-axis mode. A high risk remains.
However with the development of the strategy, it turned out that the procedure
is less dependent on the solar angle than original was accepted. That takes
some of the pressure from the further procedure.
This is better for all involved, in order not to risk that Ao-40 points uncontrolled

parallel to the magnetic axis of Earth, with the antennas to the north. That would
most likely be the end of Ao-40.

The strategy plans now to hold the Z-axis of the satellite such in the orbit, as to
have at least for a certain period in each orbit access to Ao-40. In order to
implement an satellite-internal automatic controller, actually a three-dimensional
automatic control loop of second order is necessary.
However a set of simpler differential equations could be found, which make it
possible to control the satellite movements in a predetermineable way.

To a final three-axis regulation one will only be able to approach step by step.
In a first step it is necessary to bring the spin to a value of approximately
0.4 RPM so that the spin wheels can take up the residual torque around the Z-axis.
This spin reduction must be tested, in order to be able to determine the behaviour
of the satellite as caused by the Mystery Effect.
If it is possible to still manoeuvre the satellite at this number of revolutions
the wheels can transfer the residual torque in a next step.
>From then on Ao-40 then slowly 'drifts', and one could return at any time to the
original situation with spin around the Z-axis.
If Ao-40 manoeuvring should be successful so far, the next steps can be planned.

For all these steps the appropriate mathematically physical fundamentals in
program code are to be converted.
This must also be progressed carefully. In addition trials of the code and
extended tests of the software must be done on the ground.
The transition of Ao-40 to the three-axis mode will thus still take some time.
Some steps of the strategy can take place only with a favourable solar angle.
The suitable Phase begins in November 2002.

AMSAT DL journal Sept. 2002, franc sperber, DL6DBN

================================================================================



Don Woodward wrote:

> I ran it through the translator at http://babelfish.altavista.com/ for a quick
> translation ...
>
> Three-oh stabilization of Ao-40
> With the transition of the spinstabilized mode to the Dreiachs stabilized mode
> of Ao-40 longer service life would be to be obtained with improved Squintwinkel.
> But after the driving work incident from December 2000 and the consequences from
> it new, more complicated basic conditions result. In the following contribution
> the central problems and the further procedure are described on the basis
> summarized information of the project manager Karl Meinzer, DJ4ZC, and the
> command team.
>
> After the incident in the drive system and with the withdrawn fuel several basic
> conditions had changed in such a manner that the topic three-oh stabilization
> was to be concerned fundamentally again. To these changes belong:
>
> 1. By the inclination of up to 10° (fig. 1, A) opposite the originally planned
> approximately 61° (fig. 1, B) is geometry between earth, sun and satellite
> different, which makes another strategy of the situation default necessary.
>
> 2. The so-called " Mystery Effect (ME) " makes the movement of the satellite
> uncontrollable, if the spin is so far reduced by Ao-40 that the three spin
> wheels (fig. 2) can take up the remainder angular momentum, without pushing to
> their speed limit.
>
> 3. Omni antennas round spray-end failed. Each larger change of situation, from
> the orbit level (ALAT), leads to the loss of the funkkontakts (fig. 1, C).
>
> 4. The funkkontakt straight in perigee proximity, bad by the Squint, permits
> practically no real time control of the Dreiachs automatic control loop in the
> satellite.
>
> For a long time the question was located to the satellites in the area, whether
> there is at all a safe way to be able to reach a three-oh stabilization without
> thereby to lose. In the meantime by project manager Karl Meinzer a strategy was
> developed, which permits a return to the spin mode with some probability from
> each phase of the transition in time. Thus it is not safe however yet whether
> Ao-40 can be actually transferred into the Dreiachs mode. A high risk remains.
> With the development of the strategy however it turned out that the procedure is
> less dependent on the solar angle than original was accepted. That takes
> something pressure from the further procedure. This is better for all involved
> ones, in order not to risk that Ao-40 points uncontrolled parallel to the
> magnetic erdachse with the antennas to the north. That would most likely be the
> end of Ao-40.
>
> The strategy plans now to hold the Z-axis of the satellite thereby in the orbit
> level in order to have at least for a certain period in each circulation access
> to Ao-40. In order to implement an satellite-internal automatic controller,
> actually a three-dimensional automatic control loop of second order is
> necessary. However a set of simpler differential equations could be found, which
> make it possible to control the satellite movements in a predetermineable way.
>
> To a final three-oh regulation one will be able itself to near-grope only
> gradually. In a first step it applies to bring the spin to a value of
> approximately 0.4 revolutions per minute so that the spin wheels can take up the
> residual torque around the Z-axis. This spin reduction must be tested, in order
> to be able to determine the behavior of the satellite by the Mystery Effect. If
> it is possible to still maneuver the satellite at this number of revolutions the
> wheels can transfer the residual torque in a next step. From then on Ao-40
> became slowly " sails ", and one could return at any time to the original
> situation with spin around the Z-axis. If Ao-40 should have so far come, the
> next steps can be planned.
>
> For all these steps the appropriate mathematically physical fundamentals in
> program code are to be converted. Also here is to be proceeded carefully. In
> addition Gegenchecks of the code belong and expanded tests of the software at
> the soil. The transition of Ao-40 to the Dreiachs mode will thus still last some
> time. Some steps of the strategy can take place only with according to favorable
> solar angle. The suitable Phasse begins in November 2002.
>
> AMSAT DL journal Sept. 2002, franc sperber, DL6DBN
>
> ================================================================================
> =
>
> 73's
>
> Don Woodward
> KD4APP
> AMSAT 33535
> kd4app@amsat.org
> http://kd4app.webhop.org
>
> ----- Original Message -----
> From: "Reinhard Richter" <r.richter@dj1km.de>
> To: <AMSAT-bb@AMSAT.Org>
> Sent: Tuesday, August 20, 2002 15:23
> Subject: [amsat-bb] Latest news on AMSAT-DL page
>
> Hello all,
> I've just uploaded to our AMSAT-DL webpage / AO-40-Update / Latest
> News (www.amsat-dl.org/journal/adlj-p3d.htm)an article by DL6DBN
> which was published in our recent AMSAT-DL Journal.
> It covers the 3-axis stabilization. Unfortunatelly the article is
> at time in German only. I am urgently seeking somebody who
> could translate it into English so that I can make the news page
> complete.
>
> Thank you for your attention.
>
> 73,
>  Reinhard
>  DJ1KM
>
> ----
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>
> ----
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