I just saw two point-like sources flaring in the sky in perfect sync. It was spectacular and a big surprise to me. The full event lasted at most 4 seconds. My position is in the Usera district in the city of Madrid, Spain. The time was 21:53:58 Madrid time and it happened close to Cassiopeia. Both lights were oriented vertically and the upper one was always a little more bright than the lower one.

I think it could be a satellite flare so I went to the www.satflare.com Iridium flares calculator to see if the observation matched. Iridium 28 did flare close to Madrid like 5 minutes before the event and it was close to Cassiopeia but the location didn't match so well with what I saw, the flare didn't pass exactly over Madrid, it happened to much before the time of my observation and it would explain only one flare, not two.

So I updated my TLEs in Heavensat and two objects match almost perfectly the position and time: NOSS 3-8 (A) and NOSS 3-8 (B). They move but it is true that for the 4 second time-span they did it very little (they looked still to me). So I concluded that I've observed two NOSS flares at the same time. Then I discovered this video showing the same kind of situation and I started wondering some things.


  • Why did they flare at the same time? Do they rotate in coordination and thus the Sun reflects on both surfaces at the same time in almost exactly the same angle?
  • Is this observation important for amateur observers for predicting future flares of these two satellites? Should I report it somewhere?
  • How can anyone predict the flares of these satellites? Wouldn't you need to know the exact geometry of it and the state of rotation (period and axis) to be able to do that?


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