I've had this discussion before, but am willing to revive it if needed. We have agreed on some, and disagreed on other points. Flash is a quick sharp blast of light, such as photo flash bulb.
Glint is reflection.
Glint is what the light is. Flash is what it looks like. I agree with this usage in astronomy. However, in looking at literature dating back to the first satellites, 'elevation' has been used for apparent angular distance of satellite above horizon. I'm not the one to change them.