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Re: Latest news on AMSAT-DL page



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After the incident in the drive system and with the withdrawn fuel several basic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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