Extended SAR imaging capability for ship classification

Claim 3

A method as recited in claim 1 wherein the step of processing the received signals includes: (a) Determining scatterer velocities from polynomial curve fitting to interpolated and sorted doppler processed frequency measurements over a prescribed tracking time interval; and (b) determining scatterer accelerations from the time derivatives of polynomial curve fits to frequency data.

Claim 4

A method as recited in claim 1 wherein the step of processing the received signal includes: (a) performing a weighted multivariate regression fit to processed doppler, azimuth, and elevation angle measurements to obtain cross-line-of-sight ship rotational velocities using an iterative process of minimizing error residuals; and (b) determining line-of-sight ship rotational velocity using sorted azimuth and elevation angle measurements, in conjunction with elevation angle rates determined for several bright scatterers and estimated cross-line-of-sight ship rotational velocity.

Claim 5

A method as recited in claim 3 where the step of processing the received signals includes: (a) obtaining cross-line-of-sight ship rotational velocity rates from time derivatives of polynomial curve fits to stored estimates of the cross-line-of-sight rotational velocities derived from regression solutions.

Claim 6

A method of claim 3 wherein said doppler, azimuth and elevation angle measurements are determined from Fourier transform signal processing using an antenna angle sensing system.

Claim 7

A method of claim 5 wherein the antenna system is an interferometric antenna system.

Claim 8

A method of claim 5 wherein the antenna system is a phase monopulse antenna system.

Claim 9

An airborne synthetic aperture radar system for forming high resolution synthetic aperture radar imaging of a ship target under the influence of sea state conditions, said system comprising: (a) a multiple section interferometer antenna connected to a two channel receiver; (b) means coupled to said receiver for processing signals received by said antenna from ship scatterers comprising the ship target to obtain estimates of (1) range, velocity, and acceleration of ship scatterers, and (2) ship rotational velocities and rotational velocity rates; (c) means for determining from these estimated ship scatterer motional parameters the coordinate values of the ship scatterer centers to form a high resolution image of the ship target; and (d) means for displaying the formed imagery of the ship target including a range/azimuth projection, an elevation/azimuth profile projection, and a range/elevation profile projection.

Claim 10

An airborne synthetic aperture radar system for forming high resolution synthetic aperture radar imaging of a ship target under the influence of sea state conditions, said system comprising: (a) a multiple section interferometer antenna connected to a two channel receiver; (b) means coupled to said receiver for processing signals received by said antenna from ship scatterers comprising the ship target to obtain estimates of (1) range, velocity, and acceleration of ship scatterers, and (2) ship rotational velocities and rotational velocity rates; (c) means for determining from these estimated ship scatterer motional parameters the coordinate values of the ship scatterer centers to form a high resolution image of the ship target; and (d) means for displaying the formed imagery of the ship target including a range/azimuth projection, an elevation/azimuth profile projection, and a range/elevation profile projection.

Claim 11

The system of claim 8 wherein said processing means includes: (a) means for determining scatterer velocities from polynomial curve fitting to interpolated and sorted doppler processed frequency measurements over a prescribed tracking time interval; and (b) means for determining scatterer accelerations from the time derivatives of polynomial curve fits to frequency data.

Claim 12

The system of claim 8 wherein said processing means includes: (a) means for performing a weighted multivariate regression fit to processed doppler, azimuth, and elevation angle measurements to obtain cross-line-of-sight ship rotational velocities using an iterative process of minimizing error residuals; and (b) means for determining line-of-sight ship rotational velocity using sorted azimuth and elevation angle measurements, in conjunction with elevation angle rates determined for several bright scatterers and estimated cross-line-of-sight ship rotational velocity.

Claim 13

The system of claim 10 wherein said processing means includes means for obtaining cross-line-of-sight ship rotational velocity rates from time derivatives of polynomial curve fits to stored estimates of the cross-line-of-sight rotational velocities derived from regression solution.

Claim 14

An airborne synthetic aperture radar system for forming high resolution synthetic aperture radar imaging of a ship target under the influence of sea state conditions, said system comprising: (a) means for processing the received signals from ship scatterers (1) using polynomial curve fitting to interpolated and sorted doppler processed frequency measurements over a prescribed tracking time interval to yield scatterer velocities; (2) determining scatterer accelerations from the derivatives of polynomial curve fits to frequency data; (3) performing a weighted multivariate regression fit to processed doppler, azimuth, and elevation angle measurements to obtain the two cross-line-of-sight ship rotational velocities using an iterative process of minimizing error residuals; (4) determining the line-of-sight ship rotational velocity using sorted azimuth, elevation, and elevation angle rates determined for several bright scatterers, in conjunction with estimated horizontal cross-line-of-sight ship rotational velocity; (5) obtaining the two cross-line-of-sight ship rotational velocity rates from the time derivatives of polynomial curve fits to stored estimates of the two cross-line-of-sight rotational velocities derived from regression solutions; and (6) determining from the estimated scatterer velocity and acceleration, and the estimated ship rotational parameters, the coordinate values of the ship scattering centers; and (b) means for displaying the formed imagery of the ship target including a range/azimuth projection, an azimuth/elevation profile projection, and a range/elevation profile projection.

Claim 15

An airborne synthetic aperture radar system for forming high resolution synthetic aperture radar imaging of a ship target under the influence of sea state conditions, said system comprising: (a) means for processing the received signals from ship scatterers (1) using polynomial curve fitting to interpolated and sorted doppler processed frequency measurements over a prescribed tracking time interval to yield scatterer velocities; (2) determining scatterer accelerations from the derivatives of polynomial curve fits to frequency data; (3) performing a weighted multivariate regression fit to processed doppler, azimuth, and elevation angle measurements to obtain the two cross-line-of-sight ship rotational velocities using an iterative process of minimizing error residuals; (4) determining the line-of-sight ship rotational velocity using sorted azimuth, elevation, and elevation angle rates determined for several bright scatterers, in conjunction with estimated horizontal cross-line-of-sight ship rotational velocity; (5) obtaining the two cross-line-of-sight ship rotational velocity rates from the time derivatives of polynomial curve fits to stored estimates of the two cross-line-of-sight rotational velocities derived from regression solutions; and (6) determining from the estimated scatterer velocity and acceleration, and the estimated ship rotational parameters, the coordinate values of the ship scattering centers; and (b) means for displaying the formed imagery of the ship target including a range/azimuth projection, an azimuth/elevation profile projection, and a range/elevation profile projection.