That's the Multiple Kill Vehicle.
The filmed test took place in December 2008.
The MKV mission was to destroy medium-range through
intercontinental-range ballistic missiles equipped with multiple
warheads or countermeasures by using a single interceptor missile.
During an actual hostile ballistic missile attack, the carrier vehicle
with its ...
tl;dr: It's probably a pair of small drones with LEDs or a satellite flare next to something unidentified.
To me this could look like a pair of small drones with LEDs. One remains static and the other slowly rotates so that it appears to brighten and dim as it passes the other.
Some have Lambertian distributions (see more in this answer) but with the ...