Fireball over southern England ~21:44 on 16th May?

[Rick]

There've been a number of reports of a bright fireball over southern England this evening, at around 21:44 BST. Anyone see it?

[Rick]

Too early in the evening, and too much cloud around for the Global Meteor Network cameras to catch much. There've been a few videos etc. posted on Twitter:

Thread start: https://twitter.com/UKMeteorNetwork/status/1526308926848913411

GMN image: https://twitter.com/UKMeteorNetwork/status/1526471451485913088

Door camera: https://twitter.com/HoopyKakapo/status/1526453099698827264

Door camera: https://twitter.com/ShamBaig/status/1526329482654756868

Dash cam: https://twitter.com/sndyrgrs/status/1526313754530566144

Security camera: https://twitter.com/ChrisChatfield/status/1526444472132829186

Security camera: https://twitter.com/Jen_HRRM/status/1526492159737733121

[Hugh]

The second Door Camera seems have the best recording. 

Seems they have more than a security use!

- Hugh

[Rick]

A lot of the film of the Chelyabinsk meteorite came from dashcams and security cameras. Specialised camera networks like FRIPON and GMN are all very well, but they're using very sensitive cameras because they want to be able to track an object against the stars, and that doesn't work so well when it's not completely dark. Yesterday's fireball is Exhibit A for this situation. The fireball happened at dusk, and some of the photos show that it left a persistent trail in the atmosphere, but there are very few (if any) stars also visible in the images I've seen. So far, I've not seen any Allsky camera images, but it must have been bright enough to be well recorded by any that were operating at the time.

[ApophisAstros]

Surely if they have the GPS of the cameras they can triangulate exectly where it came down?
Roger

[Rick]

Even with excellent data it can be tricky to find meteorites on the ground. I'm sure folk are trying to work out where this one landed (or splashed), but the quality of the data I've seen so far is not great, and they'll need much better data to get a good flight path. To get accurate track information you need a good position for the cameras and accurate times (to much better than a second) as well as some way of figuring out what distortions are present in the fields of view and what directions the cameras were pointing. The fixed security camera videos stand a good chance of being usable. Videos from cameras that can turn and zoom or cameras that were moving is much trickier to analyse. It can be done, and has been done for a few spectacular cases in the past, but it is quite a bit of work...

This report on the recovery of a meteorite in Slovenia a couple of years ago gives an idea of some of the work needed: https://phys.org/news/2021-09-dashcam-recovery-space-fireball-slovenia.html

To help create 3D models, local people were asked to take several photographs from known locations of buildings, telephone posts, distant mountains, and other landmarks visible in the dashcam videos. The images enabled triangulation of exact locations accurate to within a few centimeters, akin to surveyors with a theodolite. Photographs were taken on starry nights, so after calibrating against window frames and the other known points, every pixel on the original images could be mapped to a precise direction. Hardest was determining the exact coordinates from the dashcam footage of moving vehicles—for every video frame and to a precision of about one centimeter, which was long tedious work.