If you haven’t ever seen an Iridium flare, you are rapidly running out of time to do so. If this is the first you're hearing of it, a satellite flare is a brief glint in the sky caused by a passing satellite reflecting sunlight toward the Earth.
As part of Iridium’s activation of their new Iridium-NEXT constellation, they have been responsibly deorbiting their original Block 1 constellation that produce the flares. Iridium flares are so bright because of the unique design of the Block 1 satellites—the Iridium-NEXT constellation uses an entirely different design, so they won’t be producing flares.
Of the original 95 satellites in the Block 1 constellation, 35 have been deorbited (and one destroyed in a collision), with 25 deorbited in 2018 and 10 since July 1.
In order to predict flares, the satellites must be operational and have their attitudes controlled. Of the remaining 59 satellites still in orbit, 32 have already been deactivated. Another 4 are currently in the process of being deboosted. And 11 are in backup mode, which means they have been moved out of the operational orbits and may not have their attitudes as tightly controlled, also making predictions impossible.
That only leaves 13 fully operational Block 1 Iridium satellites in orbit and those are all expected to be deboosted in the coming months. So, time is running out fast!
To learn more about Iridium flares, how to see them, and what we will all-too-soon be missing, please visit https://www.iridium.com/flarewell/.
Dr. T.S. Kelso
Senior Research Astrodynamicist & SDC Operations Manager
Center for Space Standards & Innovation
Analytical Graphics, Inc.