On December 27th, 2019, Iridium 97 burned up in the atmosphere and there was a "#Flarewell" celebration. However, according to this website which seems to be VERY detailed, there are still 5 satellites still in orbit, but their orbit is decaying. I looked at all of their orbital parameters and of the 5, only 1 of them is going to fall into the atmosphere very soon. While the other 4 have perigees of 400-600 km and apogees still in the 700's km (they were originally at about 780 km), Iridium 96 has a perigee of only 261 km and an apogee of 443 km at the time of writing. It's predicted to reenter in a few months. According to the CEO of Iridium, he said that Iridium-45 (and probably the others) didn't have enough fuel and had to settle for a 10 year reentry.

Now, I know that since all of these satellites are probably tumbling, their flares will be unpredictable and show signs of their tumbling. Interestingly enough, Iridium 45 is supposed to flare according to Heavens-above soon in my area, so I figured I would take a look for the few minutes it will traverse my sky. A few other people on twitter are talking about it. Will it pass by me at the time it says? Yes, and I corroborated that with a satellite tracking website. But do I trust its prediction to flare? No, but knowing me I would look anyway.

And finally I know that there are 25 defunct, broken satellites that will not be intentionally deorbited because of lost contact, malfunction, etc. Again, many of those are tumbling and do not make predictable flares, but I have looked around and noticed that people HAVE taken pictures of their flares (even the tumbling ones) on here.

So basically, is there anyway an average Joe like me without any fancy equipment, but with access to the internet for tracking tools, predict a flare without literally watching every pass at twilight? And if an app gives a prediction for a satellite with a decaying orbit, will the unpredictability be biased to a certain result? For example, could it appear but be early by a minute? Or just not appear at all?

  • 1
    $\begingroup$ @uhoh I am aware that there are no longer ANY predictable flaring satelites, but the defunct ones that cannot be deorbited (of which there are 25) can still flare for as long as they are in orbit, which will be a fairly long time, but they will be unpredictable and show signs of tumbling. I just have no idea how to watch those unpredictable flares, unless the only way is to simply watch every pass at twilight and hope for the best. $\endgroup$
    – user34786
    Commented Feb 2, 2020 at 14:45
  • $\begingroup$ yep those aren't just for the OP, adding links to related questions helps other future readers, and it triggers them to appear in the upper-right corner where it says LINKED. $\endgroup$
    – uhoh
    Commented Feb 2, 2020 at 15:10


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.