For those people not living under a rock, there have been quite a few stories regarding the kidnapped girls in Nigeria (rock-dwellers go here to catch up). Imagine my surprise, though, at finding out that Nigeria has not just one, but two imagery satellites orbiting the Earth in Low Earth Orbit (LEO). Not only that, but the reporters for Nigeria’s media, like Punch, are asking some questions regarding those satellites and their benefits to the country of Nigeria, including whether the satellites are useful for finding the kidnapped girls.
The Director General, National Space Research Development Agency, Prof. Seidu Muhammed answers the reporter’s questions. But, for some reason the answers aren’t very straightforward. Maybe he’s speaking in a local manner, or trying to remain detached, but his answers were plain confusing. So, I will try to answer the questions in a clear way (hopefully).
One of the first questions regarding the kidnapped girls is why the satellites don’t appear to be helping in the search for the girls. The answer to this question is a little complicated, but the concepts are relatively simple.
Consider this: a sun-synchronous LEO satellite will only have a particular spot of the Earth in it’s view for 10 to 15 minutes during its orbit. The satellite’s cameras might see that spot twice a day. If kidnappers are aware (which is doubtful) of when Nigeria’s satellites can possibly see them and the girls, they can always stay hidden until the satellite can’t see them anymore–and 15 minutes isn’t too long to do that sort of thing. What’s more likely is the group of girls just aren’t outside whenever one of their satellites are overhead. And as you can see, there’s a lot of time between one satellite being over Nigeria for those short 15 minutes.
The satellite imagery payloads are just cameras. This means they work similarly to the cell phone cameras nearly everyone has. Cameras can’t see through objects. So, there’s not much that can be done with clouds blocking the satellite’s cameras view, or roofs and trees doing the same thing the clouds are doing, which is blocking the camera’s view. And like the cameras on a cell phone, the cameras on the satellite kind of have to know which area to aim at to take a photo. So if the satellite operators don’t know where the girls are being kept, they don’t know where to aim the satellite’s cameras. And taking pictures of the whole country of Nigeria takes a little time, as well as having analysts sift through all the images on the off-chance the girls are grouped outside.
Another issue with these satellites is their camera resolution of 2.5 meters, which is not terrific. This means objects 2.5 meters or bigger on the Earth’s surface can be detected and imaged by the satellite cameras. A crowd of girls will be bigger than 2.5 meters, but a single girl would be hard to detect. Even with 3 cameras, if the resolution for each of them were 2.5 meters then the same problem persists. And the cameras are only able to capture images, not video–Skybox and Urthecast are the only two satellite operators I know of with actual video capability.
Near the end, the Director General suggests that drones might be better able to locate the girls, and he isn’t wrong to suggest that. Drones are cheaper and have better persistence (staying power) than the current Nigeriasat satellites. Drones could potentially fly over suspected areas for hours at a time, using unpredictable schedules. Maybe Nigeria can still do that?
The whole conversation is interesting because it shows the gaps in knowledge the Nigeria population has, and some of the misconceptions not just they, but many in the world have about satellite imagery . The Director General’s tone seems a little too defensive, though, and the reporter is obviously not familiar with satellite operations and could’ve benefited from doing some homework. It does seem that Nigeria’s satellite arm is suffering from the same kind of messaging issues NASA is regarding all the benefits satellites give a country. Maybe they’ll figure out a better way to get the word out?
In the meantime, if you’re interested in learning more about LEO imagery operations, you can always start with this site’s Lesson 1 about LEO satellite imagery operations. There are a few more lessons after that one, too, if you have the time.