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Re: Re: What's up with Mir?

At 06:54 PM 10/14/98 GMT, you wrote:
>Jeff Johns writes:
>> I found Mir on 145.935
>> What causes the cosmonauts to change the frequency?
>I can't help wondering if theres a simple, ergonomic, answer to the
> .935 or .985 question; carelessness.

John & Jeff,

Interesting, this random flippping of channels.

Although, perhaps not the answer, I am reminded of our April Mir school
contact at the Land o' Pines School in Howell, NJ in which I was control op.

This 88 degree over head pass went well until after halfway thru when we
lost Andy Thomas as if a plug had been pulled. Fast checks on SWR, Doppler,
and antennae points gave no clue until the telebridge to Goddard suggested
the backup UHF repeater frequencies. (We had been assigned the UHF QSO freq
for the contact.) The switch (with current doppler) was made and, by gosh,
there was Andy.

Later debrief with Pat Kilroy and the folks at Goddard informed us the
problem was what they called an SEU,a Single Event Upset. As explained to us
the compact density of chips is now so fine that random cosmic rays passing
between the off-the-shelf non-hardened chips internal traces can cause these
glitches. Apparently it is not uncommon that the personal computers carried
by shuttle astronauts are crashed often enough that it is rather common to
expect lots of reboots.

This may be an area to be looked at closely for ensuring performance in the
ISS electronics package. For now VFO B maybe the answer for us on the planet.

Allen Emer, N2YAC


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