How many satellites are required to isolate an unacceptable satellite in RAIM?

To isolate an unacceptable satellite in Receiver Autonomous Integrity Monitoring (RAIM), a minimum of six satellites is required. The reason behind this is based on the concept of redundancy in the system.

When you have six satellites, the receiver can determine its position, while also being able to assess the integrity of each satellite's signal. In a scenario where one satellite is suspected to be transmitting incorrect information, the RAIM algorithm can use the remaining five satellites to confirm the position while identifying the faulty satellite. This allows the system to provide a level of integrity assurance for the navigation solution.

With fewer than six satellites, it becomes challenging to identify and isolate a potential erroneous reading, as the receiver wouldn't have enough data points to effectively cross-check and validate the integrity of the remaining signals. Thus, to ensure accurate navigation and reliable integrity monitoring, six satellites are the minimum requirement in RAIM to isolate a faulty satellite.