Weather balloons
First of all, are there any military test ranges in the area ?
I was a tech' photographer for BAe on Harrier trials, and since my job was done when the on-board cameras were fitted & loaded ( a place in SW Scotland ) I and a chum were tasked with the weather balloon.
They are sent up just before each trial flight, to help co-ordinate data on velocity etc.
The sonde in this case was about 6 x 2" in a cardboard box, packed with polystyrene.
The radar reflector below it, I kid you not, was a fold-out Christmas decoration !
As far as I remember the balloons were about 6' diameter at ground level, made of thick red rubber ( looked like a super large heavy duty condom - my chum took delight in flopping one on the bar table & raising his eyebrows at the local girls ) - they presumably expanded a lot on the way up.
I don't think the ones I dealt with would endanger a windscreen, but an engine might not like it.