I've heard that Osama Bin Laden was first found via satellite. I was wondering if it is possible to have a satellite that can scan an entire continent and find a single person or terrorists without having any specific location to look for? Can sattelites be that powerful?
I've heard that Osama Bin Laden was first found via satellite.
That isn't the case. Bin Laden was instead first found by human intelligence (interrogation, spy work). Detainees at Guantanamo revealed the name of bin Laden's most trusted courier. This eventually led to that courier being found and then discretely tailed to the compound in Abbottabad. It was suspected that someone of greater importance than a courier lived in the compound. Satellite recon was used in the process, but to develop a 3D map of the compound rather than to recognize bin Laden. Photographs of someone suspected of being bin Laden were taken, but by drones, not satellites.
Can a satellite scan an entire continent to search for someone?
No, for many reasons.
One reason is the resolution limitations of a satellite due to physics. Geostationary satellites can see almost half of the globe, but the large distance between those geostationary satellites and the surface of the Earth places severe limitations on resolution. Reconnaissance satellites (aka spy satellites) operate in low Earth orbit to overcome these limitations, but even then, the resolution is estimated to be about ten centimeters. That's not enough resolution to recognize that a face is present, let alone who's face it is.
Another issue is that those reconnaissance satellites can only see a rather small part of the globe. It takes multiple days for a reconnaissance satellite to fully map a continent. The person subject to the search can hide indoors (or simply not look up) during the very brief intervals when the satellite is in view.
Yet another issue is the huge amount of data needed to accomplish this task. Assuming good conditions, assuming the person subject to the search walks around looking up, and assuming a satellite with 0.4 centimeter resolution exists (the resolution needed for facial identification under good conditions), a continent's worth of monocolor (grey scale) imagery represents over an exabyte of data. Many such images will need to be scanned to find the elusive person of interest. Even the most powerful supercomputer is not up to this task.