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SEDSAT Passes Vibration Tests




I wanted to pass this along to all the amsat folks just as a reminder that you will have a new bird in the air in a few months!! The best thing that could happen right now is for some AMSAT folks to volunteer to help the students in Huntsville get the thing ready from the rf side of the house.

For those who know about such things a minimum vibration frequency above 95 hz is as good as a rock!

Oh by the way SEDSAT didn't cost AMSAT a penny of cash outlay but we did have wonderful support from Keith Baker, Perry Klein, Gene Marcus, Chris Rupp, the late Ed Stluka, Harold Price, and many many others at AMSAT. 

Dennis Ray Wingo
KD4ETA


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The news as of today (6/18/98, 5PM) is that SEDSAT-1 has PASSED its
vibration test. All three axes went fine. For each axis we did an up/down
sine diagnostic sweep, the body dynamics sine test, a random vibration
test, and an other up/down sine diagnositc sweep.

1. All modes were at constant frequency before and after the vibration
(within a few Hz).

2. No modes had center frequencies below 65 Hz. The lowest frequency mode
in the X and Y directions appears to have been rocking on the PAF, although
there was not enough instrumentation to prove this. Assuming that is the
case all SEDSAT body modes are above 95 Hz.

3. In the Z vibration which was expected to maximally excite internal
components we could here some distinct internal "buzz" and "hum" sounds at
particular frequencies. However, everything passed functional test
afterward.

4. During the functional tests two anomalies were observed. First was
unstable current readings from the internal main bus current sensor. This
spontaneously disappeared after some operation. The second was reduced
brightness and contrast in the PAL images after the X shake. It is possible
this is due to a lens iris problem. We will do some analysis later but do
not plan any opening of the satellite.

5. The shock test is scheduled for tomorrow.

6. Ground handling and GSE continues to be a problem. We were able to
complete all required operations, but doubts were raised about several
steps with the flight PAF that could not be fully resolved. The differences
between the T-PAF used for vibration, the test PAF used for shock, and the
flight PAF make the issue more complicated.

A really BIG thank you to everybody who has helped us get to the this
point. Especially Larry Berge and Mike Henderson at Boeing, Mike Goeser at
Goddard, Christine O'Neill at JSC, Marion Thompson at KSC, Jim Harrison at
Marshall, and the whole staff of the vibration lab at Marshall who've been
putting up with our abortive tests and every changing PAFs for quite a
while.

Mark Maier


Dr. Mark W. Maier				maier@ece.uah.edu
Associate Professor				205-890-6642
Elec. and Computer Engineering			205-890-6803 FAX
University of Alabama in Huntsville		KF4YGR
Huntsville, AL  35899		http://eb-p5.eb.uah.edu/~maier

Stereo Image Compression	SEDSAT-1	Systems Architecting




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