Final answer:
Base radial velocity is available for just a few radar "tilt" angles.
Step-by-step explanation:
Base radial velocity is available for just a few radar "tilt" angles. Radar operates by emitting a beam of radio waves and measuring the time it takes for the waves to bounce back after hitting an object. The radar antenna can be tilted at different angles to change the direction of the emitted beam. By analyzing the change in frequency of the reflected waves, the radial velocity of the object can be determined. However, this method can only give accurate results for a limited range of tilt angles.