It's a dumb objection. A mission manager was quoted using the word "diving".
It isn't the journalist but the nitpicking commentors who are clueless. The headline accurately enough conveys what is happening and the article articulates it well. Orbital mechanics isn't intuitive enough for there to be perfect fit words given human experience, human timescales, "plummet" is fine.
Plummet implies a straight-line dead fall, or close to it. It derives from lead weights (hence the similarity to "plumber") attached to a line, used for sounding depth of water or for marking a straight vertical line. The "verbing" of that noun and its figurative use to describe falling appear to be quite recent developments—Webster's 1913 only lists a noun. I'd say it's the wrong word for this case, but then I'm an opponent of using slightly-similar words interchangeably, such that we effectively have fewer words to work with. However, I'm losing that fight anyway, so who cares I guess.
[EDIT] On reflection, this is even goofier than I thought at first, since the choice of lead for those applications is precisely because it's little affected by wind, and even fares better than most things against moving water, while this is entirely about something falling faster because of its interaction with air.
I don't see why it is a dumb objection. Word choice is important, especially for journalists trying to convey information to the general public and even more so when it comes to headlines - as the majority of people won't read the article to understand the nuance.
I genuinely think a decent number of people are going to envision a situation where satellites suddenly plunging out of orbit like they would in some big budget disaster movie. You are well within your right to tell them they are thinking of the word "plummeting" incorrectly but you are fighting an uphill battle. Technical and dictionary correctness has its place but to convey information properly people must consider the vernacular.
It’s dumb because it is based on the objector imagining what an uninformed reader would imagine and thinking that anything unlike mighty Thor smiting satellites out of the sky with lightning bolts would make the word “plummet” inappropriate.
Satellites are falling relatively very fast compared to usual and some of them have or soon will burn up in atmosphere as a result, it’s a headline, not a half sentence expected to grant a degree in astrodynamics.
Likewise, why would you imagine that an uninformed reader would see the word "plummet" and understand that none of these satellites are in immediate danger of re-entry, that they will in-fact continue to stay aloft for several more months, and that in this context plummet means an orbit decaying an order of magnitude faster than expected?
You are correct, one of the meanings of plummet is a rapid descent. These satellites are rapidly descending. You are correct.
Again, though, word choice matters. Can you see where other commenters and I are coming from?
Remember that Star Trek movie trailer wherein the Enterprise (or a similar) spacecraft seemed to drop like the string had been cut? That's what I picture with "plummet".
It isn't the journalist but the nitpicking commentors who are clueless. The headline accurately enough conveys what is happening and the article articulates it well. Orbital mechanics isn't intuitive enough for there to be perfect fit words given human experience, human timescales, "plummet" is fine.