In the past I (think) I've read of artificial satellites which are designed to go into orbit quickly to deal with a short term need for observation of some type.
I'm now struggling to find a reference to this idea.
I'm not sure whether what I read was referring to the past or a system which is currently in place ?
I seem to remember that the idea was that it would be launched within days from the need occurring and wouldn't be intended to be used for longer than weeks.
I also have an idea that the orbit might be an unconventional one in order to provide optimal coverage of the area of interest.
Assuming I haven't imagined this - can anyone point me at examples of such systems ?