What light was the Falcon 9 grid fin occulting in todays SpaceX Nusantara Satu Mission live broadcast?

I backed up the time slider on the YouTube live broadcast and snapped some screen captures, cropped with python and made a GIF below.

There is some light that blinks because it's seen slowly moving through the perforated grid fins.

Moon? Light on the ground? "Chaser" spacecraft's headlights?

This is seen between about T+ 00:05:39 and T+ 00:06:00.

SpaceX Nusantara Satu Mission live broadcast

Full screen:

SpaceX Nusantara Satu Mission live broadcast

  • 1
    $\begingroup$ Everybody including SpaceX calls them 'grid fin', why introduce a new term and muddy the waters? $\endgroup$
    – Hobbes
    Feb 22, 2019 at 11:42
  • $\begingroup$ @Hobbes edited. Of course everybody including me calls them grid fins. I have no idea why I added "waffle" but it's gone now. $\endgroup$
    – uhoh
    Feb 22, 2019 at 11:53
  • $\begingroup$ I suspect it is a reflection of the moon, which was nearly full and high in the South sky from the launch site. Your GIF shows it before re-entry burn, and it also reappears (better view) just after that burn, at T+00:06:47. $\endgroup$
    – amI
    Jun 1, 2019 at 4:30
  • 1
    $\begingroup$ It would have to be reflected by the Atlantic ocean. There are also clouds or land visible between the two visible grid fins. I don't know the trajectory or location of the landing barge, OCISLY -- was there a boost-back burn? (It had the highest entry heat load to date). The angles don't make sense to me, but it looks like the Moon. $\endgroup$
    – amI
    Jun 1, 2019 at 5:31
  • 1
    $\begingroup$ You are right (except Feb, not June) -- I goofed the UTC offset. On East horizon makes sense. Maybe the smaller light just to the left is the weaker reflection. Thanks for clearing this up. $\endgroup$
    – amI
    Jun 1, 2019 at 6:19


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