[meteorite-list] OT: Iridium flares

From: ceweed_at_qatar.net.qa <ceweed_at_meteoritecentral.com>
Date: Thu Apr 22 10:07:02 2004
Message-ID: <2ae30c2adc9e.2adc9e2ae30c_at_qatar.net.qa>

Hi Matson & Folks

Matson wrote
"Marco mentioned that there is a website for predicting
flares -- this is the Heavens-Above site. Its predictions should
be quite compatible with those of my program (IRIDFLAR) as the
program author used my model for photometric brightness. The
Heavens-Above site is handy in that you don't need to know how
to run a flare prediction model. You just plug in your coordinates
or your city name, and it does all the work for you. The only
drawback is that you have to be logged onto the internet."

Matson , We owe you a great debt of grattitude
The precision of the flare predictions is breathtaking at times
set the gps on & count down to the second
good for filling in time un this meteorite sparse land
allthe best
Colin


----- Original Message -----
From: "Matson, Robert" <ROBERT.D.MATSON_at_saic.com>
Date: Saturday, October 19, 2002 10:00 pm
Subject: [meteorite-list] OT: Iridium flares

> Hi Marco and List,
>
> For those not interested in more info on Iridium flares, delete now.
> (This is a bit off-topic for the Meteorite List, but since many
> meteorite afficionados are also interested in bolides, there is
> a tenuous connection.)
>
> Marco wrote:
>
> > For those who do not know, this is a series of artificial
> > communication satellites, initiated some years ago (I believe
> > we started to first see them in 1997) ...
>
> This is correct -- summertime of '97.
>
> > ... in order to provide for (expensive) satellite telephone
> > from anywhere in the world.
>
> Expensive is right. The marketing plan for Iridium was questionable
> at best. The phones are bulky and very expensive themselves, and
> the per-minute telephone charges were many dollars per minute. Of
> course, if you're working in Antarctica on some research project,
> you aren't likely to have a nearby cellular site! ;-)
>
> > The network entailed as much as 70 satellites, most of which
> > have indeed been launched.
>
> Over 90 have been launched -- perhaps around 95 by now. About
> a dozen of these have failed, and of that dozen several have
> already reentered the atmosphere. 91 remain in orbit at the
> present time.
>
> > The project failed as the company in question got bankrupt,
> > but the satellites are still there although they should be
> > phased out and re-enter as was the plan some time ago when
> > the company was dismantled and the network closed.
>
> Actually, the DoD bought out Iridium ILC's interest in these
> satellites (for pennies on the dollar) and they continue to
> operate to this day. The DoD was the primary customer of
> the system, so they had a vested interest in keeping it alive.
>
> > They carry a large antenna panel which reflects beams of
> > sunlight.
>
> There are 3 main mission antennae (MMA), any of which is
> capable of reflecting solar glints down to the ground depending
> on the geometry. These MMAs are quite large -- door-sized (and
> a large door at that). Under the most favorable geometry, an
> antenna can produce a glint as bright as magnitude -8.5, and
> thus are quite visible in daytime. (I've seen several dozen
> of these daytime Iridium flares).
>
> Back in the summer of 1997, shortly after the first 5 satellites
> were launched, the "flare phenomenon" was serendipitously
> discovered by an amateur satellite observer. The flares were
> totally unforseen by the satellite builders. Working with a
> network of observers and the spacecraft designers, I was able
> to quickly cobble together a program that would predict future
> flares for any observer. As more flare observations came in,
> the brightness curves were tweaked until I finally had a very
> reliable flare predictor. Indeed, you can set your watch by
> these flares -- they're that reliable.
>
> What makes the flares predictable is that the satellite orientation
> is very accurately maintained and thus predictable for weeks into
> the future. Marco mentioned that there is a website for predicting
> flares -- this is the Heavens-Above site. Its predictions should
> be quite compatible with those of my program (IRIDFLAR) as the
> program author used my model for photometric brightness. The
> Heavens-Above site is handy in that you don't need to know how
> to run a flare prediction model. You just plug in your coordinates
> or your city name, and it does all the work for you. The only
> drawback is that you have to be logged onto the internet.
>
> Anyway, for the few people left in the world who have never seen
> an Iridium flare, make the effort to see one. They are fabulous,
> and great for getting kids interested in astronomy.
>
> Cheers,
> Rob
>
>
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Received on Sat 19 Oct 2002 10:53:54 PM PDT