Discuss how real-time or near real-time imagery can help border-security officials monitor activity along a border (you can use a general border or discuss a specific international border). In your discussion provide a description of at least one imagery platform and sensor could be used to monitor a border. 
Platforms can be manned or unmanned aircraft, such as UAVs, airplanes or aerostats (blimps), or terrestrial platforms could be poles, trees or buildings. 
 
 
Sensors can be still cameras, video cameras, infrared cameras, multi-spectral sensors, and lidar sensors.  
Note that satellites generally do not have revisit times that allow for near real-time monitoring, but a few satellites do monitor the Earth daily, such as the Planet Labs constellation.