There are several ways to go about it. First would be to use a single 2-D array starting straight down (or possibly straight up) and then use a lens (or mirror) to map the 360° region between two reasonable angles of declination onto the imager. Another would be to use a linear around mounted vertically but tipped at an angle toward the ground and sweep it in a circle as the drone flies around. Another is to use a single IR phototransistor to act as a single-pixel camera and then have a mechanism sweep it up and down as well as around.Ok, I don't care anymore about the secrecy or I won't get anywhere!
The purpose was to equip and build a system around a drone that could detect fires and report their coordinates to some fire departement or make an automatic phone call or so!
Let's imagine I have a drone that has some lifetime given buy some battery and that is somehow programmed to watch a specific area. In that period of time, the drone must scan that area and search for heat sources aka fires and report the coordinates or make some kind of automatic call or set an alarm to alert humans of a possible fire! This was the basic idea. Then, for a long term, it would be to create a bigger network that could cover larger areas!
You don't need good coordinates, either. If the drone reports its present location (using GPS) and then reports a possible fire one a bearing that only has a 45° resolution and has no distance measurement of any kind, that is almost certainly good enough for someone to quickly check if there really is a forest fire our there -- after all, once you are given notice that a fire might exist within a region that might be even a couple of thousand square miles, it is a pretty trivial matter to go look and determine whether there really is one anywhere in that area.