State of the art
Nice to know we can make this stuff -- but not quite so nice to know that we have to rely on someone else to launch it...
The RAF has acquired a satellite that can beam live video footage from space, the head of the air force told an industry gathering in Surrey today. The Carbonite-2 satellite, built by Airbus Defence and Space subsidiary Surrey Satellites, based near Guildford, will be used by British military intelligence folk as a concept …
You can't quite do one spot each day. This is in a 90minute orbit, so gets 18 slices of the Earth each day.
Since it only images a 5km wide swath you don't get very complete coverage - basically you get 5km wide lines 2000km apart. You can slowly precess the orbit so that you can fill in the coverage over any spot but that takes a while
"basically you get 5km wide lines 2000km apart"
The numbers: the Earth's circumference of 40000 km (plus ~7-75km - a little bit) / 5 km swath width = 8000 swaths. Five satellites means 1600 swaths per sat, or 1600 orbits per sat, to cover the equator. If the orbital period is 90 minutes then we're looking at 1600 orbits * 90 minutes per orbit = 144000 minutes = 2400 hours = 100 days (to cover the equator).
(if there's a bad in that maths, I can't see it, but welcome corrections - I'd sooner be right than wrong)
However, each satellite, in its Sun-synchronous orbit, which is nearly polar, is covering a 'gore' of the Earth's surface which, whilst being 8000 km wide at the equator, narrows as you move further north and south, which means you can get more frequent coverage; in a polar orbit, where the satellites passed directly over the poles, one would be passing overhead every 18 minutes.
Fwiw, at 60 deg north or south, the circumference, and thus the gore width, is half that of the equator.
But yes, this is the most important limitation of the system. I can't see them having a significant cross-range capability either, so once they're up they're not going to change their orbits by very much, making their overflights predictable - it should be easy to avoid being observed by them.
The live video feature would seem to have limited utility too. It would appear, from the article, that it "can collect 50fps imagery in two-minute bursts." which, presumably might also give you 25fps x 4 min. Such a narrow window of observation means that the people you want to observe would have to deliberately schedule their operations and move to the right place to allow you to observe them.
The MOD's claim that they'll provide an "ability to surveil particular locations and pick up physical changes at short notice" doesn't seem plausible.
I reckon they'd bet very useful indeed, for high-res mapping and scientific research though.
"it should be easy to avoid being observed by them."
Maybe. It depends what you are doing. If the UK MoD is interested, there's a good chance others are too, possibly a data share with the other 5 eyes would give more frequent coverage and if there's that level of interest, then probably everyone with an interest is watching too, even of not sharing with each other.
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