[Datastream #HLJ-915280]: GOES-east Signal Noise

Hi Fred,

re:
> The Unidata GOES-east data received via ADDE has a lot of noise and
> bad lines.

We began to notice this yesterday morning.

re:
> Checking other web sites of GOES data do not show these
> noise spots and bad lines.  In the past, these kind of image problems
> have been caused by problems with the GOES receiving antenna.  Some of
> the possible causes include having the antenna poorly aimed at the
> satellite, snow on the dish, obstructions on the feed horn (including
> snow and wasp's nests), local RFI interference from cell phones,  and
> marginal receiving electronics which are about to fail.

Got it.  Since there is no snow in Boulder at the moment, and since
is not yet late enough in the year for lawn mowing (one rammed into
the GOES-West dish last year, and the result was in total loss of
signal), we were at a loss for what the problem could be... until
we did an inspection.

re:
> Have you noticed the problems with the GOES-east data, and do you know
> what is causing the problem?

We did, and we do now.  It seems like one of the high wind episodes
must have spun the dish enough to put its alignment on the very edge
of usability.  Starting sometime on Sunday, this marginal condition
was enough for noise to start appearing in sectors being produced
on the GOES-East ingester.  By Monday, the problem had gotten bad
enough to force and end-user (not you) to submit an inquiry about
not being able to get data listings off of the ADDE server... the
problem was basically that the processing of data slows as bad data
increases, so the many folks that were hitting the server for data
were causing load averages to go through the roof (I saw loads as
high as 40 this afternoon).  After we realigned the dish this afternoon
and killed off some listing processes that had been running for over
a half hour, the load average dropped back to acceptable levels. 
At the same time, the realignment has resulted in the data being
clean once again.

Just so you know, we also re-pointed the solid dish we had been
using for GOES-South America surveillance to GOES-East as the
signal to noise on the solid dish is much better than for the
mesh dishes currently being used for GOES-East and GOES-West
ingest.  We plan on swapping goeseast and goessouth roles probably
sometime tomorrow.  Since we will do this by changing IP addresses,
you will not have to do anything on your end.  If we can do the
swap quickly enough, there shouldn't be any missed coverage as we
plan to do the swap during a data ingest lull.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: HLJ-915280
Department: Support Datastream
Priority: Normal
Status: Closed