Detects foreign spaceships approaching our planet.
New players will usually be fine with just one Radar!
It has different jobs (see Technology Center for more info on job unlocking):
Tells you if an enemy fleet is Raiding you, it takes 2 minutes to get the scan results. This scan doesn't provide any intel on enemy forces except for the player's name. It is the fastest scan since you get results in just 2 minutes compared to other types of scans.
Every 10 minutes it runs a Simple Scan.
Every 30 minutes it runs an Advanced Scan. Note that this job is expensive, you should disable it temporarily when running low on resources. It also runs 3 times slower than the simple Automatic Scan so it might not detect fast raids in time.
When getting raided, depending on what you want to do, the following are good strategies:
The Advanced Scan runs every 10 minutes, but the Advanced Automatic Scan does so every 30, which, with Hyperspeed, enemies could go undetected. A good strategy is to have 2 or more Radars running at the same time, so automatic scans happen more often. You do need to time/calibrate them right. For example, if you want to run Automatic Advanced Scans every 15 minutes, build 2 Radars and start the first job, then wait 15 minutes and start the job in the second Radar.