Originally Posted by
HOVIS
Second stage of the Atlas V/Starliner perhaps.
That would make sense, thanks. Roughly 24 hours after launch it's still somewhere near the 98nm initial trajectory, so not yet burning up, but is high enough to catch the sun, and crosses the sky about four times faster than the ISS. That assumes that the initial trajectory is more or less orbital - which would make sense, you want something fairly stable in case of delays, rather than find yourself plummeting earthwards only a few minutes after planned separation. In addition the path was in the same general direction as the ISS (maybe 15 degrees out?). And of course it would be following up behind - I believe SOP from year dot of orbital rendezvous has been to do that.
I guess heavens-above don't bother with ephemeral and less-predictable events.
A genuine thank you.