Iridium Flares

This morning I captured an Iridium Flare on video. What, you might ask, is that?

There is a constellation of 66 spacecraft orbiting Earth which make up a world-wide satellite phone system. The system provides coverage all over the Earth. The spacecraft look like this. Besides having two solar panels, barely visible in this image, there are three highly reflective rectangular antennae. These antennae communicate with phones on the ground and with other Iridium satellites.

Source: Wikipedia Commons


The antennae are also excellent mirrors which reflect sunlight in orbit. Those reflections sometimes pass over the surface of the Earth as a bright patch of light about 10 km (6.1 mi) wide. If you know when and where to look, the reflections can be seen easily at night and sometimes in broad daylight. They last only a few seconds. They can be many times brighter than Venus or Jupiter. This morning one of the brightest possible reflections, or flares, passed directly over me. I wanted to try recording it on video.

When and Where to Look

There are websites that provide this information. An easy one to use is Heavens Above. You will need to set your location by using the Change Your Observing Location link at the left side of their window. Once you’ve done that, it should appear in the top right of the window. Bookmark the url for later visits. Notice the many choices at the left of things to explore.

Next click on the link at the left side of their window called Iridium Flares in the Satellites category. You should soon see a list of upcoming flares visible to you at your site if there are any. Note the Brightness column. Pick one with a large negative magnitude. Those are the brightest. Click on it’s link at left to see more. You will see a star chart and details about the flare. The satellite track is shown and a marker for the location of the bright flare along that track.

What I Expected This Morning

Heavens Above gave me this chart for this morning’s flare. It was going to be near Orion’s shoulder at 6:30:50 am.



At that time, the sky was going to be well into twilight. Stars wouldn’t be visible. So, I went outside a little before 6 am to photograph Orion in order to know where to point my video camera later. Orion was exactly where I expected. I zoomed, cropped, and enhanced the image to match the chart above.



Here are the details of the flare provided by Heavens Above. It provided the altitude and azimuth for the video camera pointing directions.


Video Result

I set the video camera to point at the spot in the bright sky. Just before the flare was to shine, I started the recording and looked up to watch. There it was, incredibly bright at magnitude -8. It brightened and faded within 3 or 4 seconds. I stopped the camera and went inside to check the result. Got it!

For best viewing, watch this video on a desktop monitor and set to full-screen HD. Look just barely right of center at the 5 second time. It is very brief. What do you think of that?


11 thoughts on “Iridium Flares

  1. I couldn’t see it either, until I went full-screen. Then, there it was, in all its glory! Very interesting: not only the phenomenon, but that you were able to catch it.


  2. Your topic of iridium flares made me think of the word the word iridium itself, which I figured must come from the Latin word for ‘rainbow,’ īris (with stem īrid-, as in iridescent). The American Heritage Dictionary says the name was created with reference to the colors produced by dissolving the element in hydrochloric acid.

    Like shoreacres, I couldn’t see the flare either until I went full-screen. The low resolution apparently swallowed the flare in the small view.


    • This too… [] the Iridium constellation of satellites was originally to be 77. That is also the atomic number for the element Iridium. That’s why they chose that name. Today, 66 satellites do the job.

      I couldn’t see it on anything but my large monitor. It would have been easy to miss in the sky if I didn’t look in the right place.


  3. Nice capture!

    The company I worked for in the satellite battery business, Eagle Picher Industries, built the batteries for Iridium. They were the same kind I was involved with, nickel-hydrogen, but it wasn’t one of my projects. It was a big, expensive program. Most satellite projects are singles. Even GPS has only 31 satellites currently. The expense was why Iridium was never a commercial success, but the birds were up there now and are obviously still in use. It is the only telephone system I’m aware of that is effective anywhere on earth. I’m sure Air Force One uses it.

    These are long-lasting batteries, but a challenge for any chemistry. The mid-earth-orbit design adds up to a lot of cycles and no maintenance calls accepted!

    Liked by 1 person

    • That is interesting to hear you were in that business. It is an impressive constellation of satellites. I visited their web site to read more about their products and technology. Right you are about no service calls.

      My son-in-law works for NOAA on the next generation GOES weather satellite. Once I get him started talking, he has a wealth of interesting things to talk about. I can keep up with most of it. Now and then, I get snowed under.


      • Thanks for educating me about these. The importance of mapping the sky has been so useful for me, although I live in an area where there are just too many buildings to watch anything. I will check out ‘Heavens Above’. Jim, thanks so much for this educational blog, I was able to see the lights in your video, and for me it’s so important to learn these because this is precisely the sort of thing that throws uneducated people to think that these reflections are either airplanes, helicopters, or what have you, UFO’s. Thank you!

        Liked by 1 person

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