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Iridium Flashes & GSOC ... the FACTS

Come on now, folks ... it seems to me that we're being grossly unfair in
our judgement of the German Space Operations Center (GSOC)
http://www2.gsoc.dlr.de/satvis/ and the superb service they are providing
us for FREE!  Here's the complaints which have been repeating in the Emails
I've seen lately ::

1.  Keps are old ... not true!  I checked the keps on all visible Iridiums
for the next 7 days and they were all only FOUR days old!  Since the birds
are in a very stable orbit and the Attitude Control Systems (ACS) keep them
smack dab on the money, there is absolutely NO practical need for more
frequent updates to the Keplerians. In the worst case I have ever
witnessed, the flare occurred approximately 30 seconds late!

2. Difficult to comprehend the output?  You are provided a clearly laid out
table with 8 values per flare.  The first 5 entries show you::

     - date & time of the flare    (in *your* Local Time!)
     - Intensity or Magnitude      (how bright it's going to be at YOUR
     - Azimuth & Elevation    (where you should look to see the flare)

Seems pretty clear doesn't it?   ... that's ALL you need to observe the

The last column gives the *name* of the particular Iridium bird producing
the flare .. If you click on that name, all the technical details for that
bird are shown, including the Keplerian element set showing date & time of
the epoch.  If you click on the "Local Time", you are provided more detail
INCLUDING A MAP/PICTURE showing your location in relation to the 'Flare
Center'.  This reference to the "Flare Center" is more than likely to be
the culprit causing confusion ... for all practical intents and purposes,
this data can be totally IGNORED if it's confusing.  Let's take a real
     For my location, the table shows a flare occurring on 05 Aug @
21:54:43 EDT.  The magnitude will be -1 (brighter than Mir!) and it will
occur at 10 deg elevation, 350 deg azimuth.   NOW comes the potentially
confusing part ... for each 'flare', there is an optimum spot on the face
of the earth where the brightness of the flare will be highest ... that is
called the 'Flare Center'.  If I chose to (I don't), the table shows me
that I could jump in the car, drive 83.2 km due East and I would be right
ON that optimum spot ... further, if I DID that, the magnitude of the flare
as seen by me at that point would increase to -4!  (That's about half as
bright as a full moon).

I feel certain that if those experiencing confusion would only read the
"Iridium Flare Help Page", all confusion would be dispelled ... that page
presents a well done tutorial which explains everything you ever wanted to
know about flares and how to view them.  Yes, I know ... ONLY when 'all
else fails, read the documentation'.

By the way, the GSOC also provides you with a table of visible Mir sighting
opportunities for the next 10 days as well, and they have been extremely
accurate in my experience.  The tables have proved to be so clearly
presented that I have been able to fax them to non-Internet friends who
have been delighted by the results.
SO, please don't be frightened away by a few negative comments .. check
into the GSOC site, print listings for Mir and Iridium flares and try it
yourself ... I guarantee you'll like it!

73,  Ron    W0PN/3

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