What’s an Iridium?

What’s an Iridium?

I’ve been asked this question a lot lately. It probably has something to do with my occasional, somewhat cryptic Facebook posts that simply say something like ‘Iridium 70’.

Simply speaking, Iridiums are communications satellites. There are currently 66 active Iridium satellites, a few spares and a few dead satellites in orbit around the earth about 485 miles up. Each of the satellites has 3 highly polished antenna panels near its bottom which point toward earth to receive and transmit satellite phone signals.

Iridium Sat

If you’re in the right place at the right time you can see the sun reflect off of the panels as it passes more or less overhead. The reflection, called an ‘iridium flare’, looks like a very slow moving meteor and can be barely visible to very bright depending on how close to directly overhead it passes.

Iridium 54

For the past few months we’ve been out in the evenings or early mornings doing a bit of flare watching. Its not too hard to do, you just have to know when and where to look and have a fairly dark location with a low horizon to watch from. Fortunately, there are apps out there for smartphones that can tell you when and where to look from practically anywhere. My current favorite for iPhone is ‘Sputnik!’ and with a couple minor settings tweaks will show both nighttime and daylight flares.

sputnik iphone

The Iridium apps I’ve come across so far range from free to just a couple of bucks. That’s pretty cheap entertainment if you ask me. Don’t have a smartphone? Give the Heavens Above website a try. Simply create a free account, enter the longitude and latitude of your viewing location (Google Earth can help with that) and click on the Iridium Flares option to get the info you need.

Find yourself a relatively dark place to watch and, if possible, a dark place with a fairly low horizon – you need to be able to see down to about 20 degrees above the horizon.  Parking lots are great places to watch, as are cul-de-sacs.  Streetlights are annoying but most of the time they’re not deal killers.  Got access to a pasture?  You’re good to go…just be sure to watch where you step.  Don’t know where 20 degrees is?  Try this…Make a fist with each hand, put one on top of the other and hold them out straight in front of you.  Place the bottom of your bottom hand on the horizon and the the top of your top hand will be fairly close to 20 degrees.  Some of the apps, like Sputnik!, have features to point you to the right spot in the sky to look.  If you’re using a data printout from Heavens Above having a compass or a really good sense of direction will be pretty handy.

Sputnik Screen 1 Sputnik Screen 2









OK, so you have your app installed or a printout of your Heavens Above info in hand and you’ve picked out a flare that is supposed to be visible from the location you’re going to watch from…what next?  Head outside to the spot you’ve picked to watch from.  Be sure to go out a few minutes early to give your eyes time to adjust to the darkness.  Go ahead and turn on your app or pull out your compass and data printout and begin to get your bearings (for those of you using a compass and a paper printout, try to use a red filter on your flashlight to preserve your night vision).  At 30 or so seconds out begin watching the spot that your app of the Heavens Above data points you to.  Often times you’ll be able to find the satellite before it ‘flares’ as well as after.  That’s it.  Sounds simple right?  Well, it is.  Try to pick out fairly bright flares for your first couple of trys.  Once you know what to look for the rest become easier.

Now Get Out! and see and Iridium for yourself!

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