Homing Sensors is a technology that can be researched at the Research Center in Tech Level 4. It costs 300 Food and 200 Nova, and gives the projectiles of Anti-Air units and Turrets homing capability, making them vastly more accurate.
If the enemy employs a lot of aircraft, this upgrade is an absolute necessity, as it's very hard to hit a moving aircraft without it.
"By developing these new sensors specialised against Aircraft, you can grant all your Anti-Air units an additional attack bonus, making them even more lethal."
—Manual description