Methods and systems of relative navigation for shipboard landings

A method for guiding the approach and landing of an aircraft, the method comprising:

• receiving navigation information from the aircraft;
• receiving navigation information from an aircraft carrier;
• integrating the navigation information from the aircraft with the navigation information from the aircraft carrier to determine a stabilized relative position and velocity vector between the aircraft and the aircraft carrier;
• and
• based on a last known state of the aircraft carrier, providing an estimate of the relative velocity vector and the relative position at a point forward in time to complete an autonomous shipboard landing,
• wherein integrating the navigation information comprises performing the following on a processor:
• determining a combined GPS code based an uncorreted GPS code and carrier double differences combined with a predicted GPS code and carrier double differences and the received navigation information from the first and second objects;
• calculating a baseline relative position vector based on the received navigation information from the first and second objects;
• calculating a double difference code based on the baseline relative position vector;
• calculating a relative position and velocity vector based on the double difference code, the combined GPS code and the received navigation information from the the aircraft and the aircraft carrier;
• and
• stabilizing the relative position and velocity vector,
• wherein the estimates of the stabilized relative position and velocity vector are computed by differencing absolute positions of the ship and aircraft in a first operational mode,
• wherein the estimates of the stabilized relative position and velocity vector are computed using a relative navigation Kalman filter based on one of double differenced single frequency or narrow lane pseudo-range (code) measurements in a second operational mode, and
• wherein the stabilized relative position and velocity vector are computed in the relative navigation Kalman filter based on double differenced single frequency or narrow lane code and double differenced single frequency or wide lane carrier measurements in a third operational mode.

A computer-readable medium having computer-executable program instructions for a method for determining relative position and relative velocity between an aircraft and a seaborne aircraft carrier as the aircraft approaches the aircraft carrier, the method comprising:

• integrating the attitude and position of the aircraft carrier with the attitude and position of the aircraft to produce a relative position;
• integrating the velocity of the aircraft carrier with the velocity of the aircraft to produce a relative velocity;
• and
• constructing the reference trajectories for the relative position and velocity based on a prior data link between the aircraft and the aircraft carrier,
• wherein the integrating steps comprise performing the following on a processor:
• determining a combined GPS code based an uncorreted GPS code and carrier double differences combined with a predicted GPS code and carrier double differences and the received navigation information from the aircraft and the aircraft carrier;
• calculating a baseline relative position vector based on the received navigation information from the aircraft and the aircraft carrier;
• calculating a double difference code based on the baseline relative position vector;
• calculating a relative position and velocity vector based on the double difference code, the combined GPS code and the received navigation information from the aircraft and the aircraft carrier;
• and
• stabilizing the relative position and velocity vector,
• wherein the stabilized relative position and velocity vector are computed by differencing absolute positions of the carrier and aircraft in a first operational mode,
• wherein the stabilized relative position and velocity vector are computed using a relative navigation Kalman filter based on one of double differenced single frequency or narrow lane pseudo-range (code) measurements in a second operational mode, and
• wherein the stabilized relative position and velocity vector are computed using the relative navigation Kalman filter based on one of double differenced single frequency or narrow lane code and one of double differenced single frequency or wide lane carrier measurements in a third operational mode.

An on-board navigational system for an aircraft, the system comprising:

• a first processor adapted to perform real-time computations necessary for recording absolute measurements of the aircraft's position and velocity, wherein the first processor is further adapted to integrate position and velocity measurements with respect to the aircraft;
• a second processor adapted to perform real-time computations necessary for receiving position and velocity measurements from an aircraft carrier, wherein the second processor is further adapted to estimate position and velocity errors with respect to the aircraft, estimate position and velocity errors with respect to the aircraft carrier, and estimate the relative position and velocity between the aircraft carrier and the aircraft at a point forward in time to complete an autonomous shipboard landing;
• one or more position sensors coupled to the first processor, the sensors adapted to detect the position of the aircraft;
• one or more inertial sensors coupled to the first processor;
• the sensors adapted to detect the inertial movements of the aircraft;
• and
• a navigation avionics platform, coupled to both the first and second processors, wherein the platform is further adapted to provide ship state and GPS measurement data from the aircraft carrier to the second processor, and to receive relative navigation data from the second processor based on a previous ship state,
• wherein the second processor includes a relative navigation Kalman filter (RNKF) that operates in the following modes:
• first mode where the relative navigation solution is computed by differencing absolute positions of the ship and aircraft,
• second mode where the relative navigation solution is computed in a relative navigation Kalman filter based on double differenced single frequency or narrow lane pseudo-range (code) measurements,
• third mode where the relative navigation solution is computed in the relative navigation Kalman filter based on double differenced single frequency or narrow lane code and double differenced single frequency or wide lane carrier measurements.

An apparatus guiding the approach and landing of an aircraft, the apparatus comprising:

• means for receiving navigation information from the aircraft;
• means for receiving navigation information from an aircraft carrier;
• means for integrating the navigation information from the aircraft with the navigation information from the aircraft carrier to determine a relative velocity and a relative position between the aircraft and the aircraft carrier;
• and
• based on a last known state of the aircraft carrier, means for estimating the relative velocity and the relative position at a point forward in time to complete an autonomous shipboard landing,
• wherein the means for integrating further:
• determines a combined GPS code based an uncorreted GPS code and carrier double differences combined with a predicted GPS code and carrier double differences and the received navigation information from the aircraft and the aircraft carrier;
• calculates a baseline relative position vector based on the received navigation information from the aircraft and the aircraft carrier;
• calculates a double difference code based on the baseline relative position vector;
• calculates a relative position and velocity vector based on the double difference code, the combined GPS code and the received navigation information from the aircraft and the aircraft carrier;
• and
• stabilizes the relative position and velocity vector,
• wherein the estimates of the stabilized relative position and velocity vector are computed by differencing absolute positions of the ship and aircraft in a first operational mode,
• wherein the estimates of the stabilized relative position and velocity vector are computed using a relative navigation Kalman filter based on one of double differenced single frequency or narrow lane pseudo-range (code) measurements in a second operational mode, and
• wherein the estimates of the stabilized relative position and velocity vector are computed using the relative navigation Kalman filter based on double differenced single frequency or narrow lane code and double differenced single frequency or wide lane carrier measurements in a third operational mode.