Radar coasting during data dropout

A method for determining the location and velocity of a target in terms of range-state and Cartesian state, said method comprising the steps of:

• sensing the target with a radar, to generate measurement data;
• determining from said measurement data instantaneous range-state and covariance;
• estimating from said instantaneous range-state and covariance an instantaneous perpendicular speed of said target;
• converting said measurement data in Cartesian coordinates to produce measurement data in Cartesian coordinates;
• Kalman filtering said measurement data in Cartesian coordinates to produce filtered Cartesian states and covariance;
• updating said filtered Cartesian states and covariance with said instantaneous perpendicular speed to produce improved Cartesian states and improved covariance with improved target velocity;
• coasting said improved Cartesian states and improved covariance at times when said measurement data is interrupted by the steps of:
• propagating the improved Cartesian state and improved covariance, and adding effects of gravity in Cartesian coordinates to the improved Cartesian state;
• calculating a contribution of gravity in a direction of the radar line-of-sight using the improved Cartesian state;
• computing a centrifugal acceleration with respect to the range-state using said improved target velocity in Cartesian coordinates;
• propagating the range-state;
• and
• adding the contribution of gravity and centrifugal acceleration on the range-state as computed in said steps of calculating and computing.

A system for generating target location and state to support trajectory coasting, said system comprising:

• a processor executing instructions for performing the steps of:
• Cartesian-coordinate-filtering range and angle information associated with said target to produce Cartesian-coordinate state information having a first quality;
• filtering range and Doppler information associated with said target to produce a filtered range state including range acceleration;
• determining from said range acceleration an instantaneous perpendicular speed;
• estimating, from said instantaneous perpendicular speed and said Cartesian-coordinate state information with said estimated Cartesian velocity to produce Cartesian state information with a higher quality than said first quality;
• propagating said estimated Cartesian velocity in time to produce range acceleration information, and combining said range acceleration information with said range state estimate to thereby produce target location and state.

A method for determining the location and velocity of a target in terms of range-state and Cartesian state, said method comprising the steps of:

• sensing the target with a radar, to generate measurement data;
• determining from said measurement data instantaneous range-state and covariance;
• estimating from said instantaneous range-state and covariance an instantaneous perpendicular speed of said target;
• converting said measurement data into Cartesian coordinates to produce measurement data in Cartesian coordinates;
• Kalman filtering said measurement data in Cartesian coordinates to produce filtered Cartesian states and covariance;
• updating said filtered Cartesian states and covariance with said instantaneous perpendicular speed to thereby produce improved Cartesian states and improved covariance with improved target velocity;
• coasting said improved Cartesian states and improved covariance at times when said measurement data is interrupted, by the steps of:
• propagating the improved Cartesian state and improved covariance, and adding the effects of gravity in Cartesian coordinates to the improved Cartesian state;
• calculating a contribution of gravity in a direction of the radar line-of-sight using the improved Cartesian state;
• computing a centrifugal acceleration with respect to the range-state using said improved target velocity in Cartesian coordinates;
• propagating the range-state;
• and
• adding the contribution of gravity and centrifugal acceleration on the range-state as computed in said steps of calculating and computing.