Yes, an incoming impactor was detected before impact. Object 2024 UQ was spotted (by the ATLAS telescope system) and reported back to the NEOCP (the Minor Planet Center‘s Confirmation Page). A trajectory solution determined that the object was likely to hit the Earth, and in fact likely already had by that point. Sure enough, sky monitors confirmed a flash in the expected area- in the Pacific, off the California coast.
This is the third pre-impact detection this year, and folks, this is how it works. Global telescopes (here, ATLAS’s Haleakala observatory) report their detections to one or both computational clearinghouses (either the Minor Planet Center, or its European equivalent). After three or more coordinates are in hand, a trajectory can be computed, either by the two clearinghouses, or at times by the observatory reporting the coordinates in fortunate cases. The asteroid centers then send out alerts, depending on the urgency. Some asteroids are passing Earth closely, meaning they cross the sky quickly and leave soon. These bodies need to be observed in a limited window, before they ‘escape.’ In the case of a trajectory that computes an impact, well, escape isn’t the right word, eh?
I am reminded of asteroid 2008 TC3, which was discovered shortly before impact in the Sahara Desert. A telescope with a spectrograph managed to get onto it before too long. In the Sahara, fragments were discovered- the Almahata Sitta meteorite. With both an asteroid characterization (crude though it was) and a meteorite sample in hand. we learned a lot about the correspondence. We know meteorites are fragments of asteroids, but without any connection between the two, how do we fit the puzzle pieces together? We’re getting better at this, definitely. But not in the case of 2024 UQ- the pieces are now in the ocean, as with so many meteorites before it.
We are getting more search telescopes (and bigger ones). If we can detect impactors sooner, and with better telescopes, we will be able to fit more puzzle pieces, like 2008 TC3/Almahata Sitta. The future of meteoritics, planetary defense, and geochemistry/cosmochemistry is looking up.