How many operational satellites are required for NAVSTAR GPS, and how are they distributed?

For NAVSTAR GPS, a constellation typically comprises a minimum of 24 operational satellites that are necessary to ensure global coverage. These satellites are arranged in six orbital planes, with four satellites in each plane. This specific arrangement allows the system to provide adequate coverage to users anywhere on the planet, ensuring that at least four satellites are visible from virtually every location at any given time.

The six orbital planes are inclined at approximately 55 degrees to the equator, which helps to provide uniform coverage and redundancy, allowing for better accuracy and reliability of triangulating a position. Each satellite transmits signals that enable receivers to calculate their position by triangulating from at least four satellites simultaneously.

The correct answer reflects the structural layout and number of satellites necessary for optimal functioning of the NAVSTAR GPS system, ensuring comprehensive global coverage and improved positional accuracy.