Patent ID: 11873123
Assignee: UNITED STATES OF AMERICA AS REPRESENTED BY THE SECRETARY OF THE AIR FORCE
Field: Transport (Mechanical engineering)
Classification: CPC B  G | IPC B  G

Claim 2:
3. A module comprising: a central processing unit programmed to determine an aerospace vehicle's position with respect to the Earth, comprising determining the aerospace vehicle's pose estimation between two points in time and/or attitude with respect to the Earth wherein:
a) determining the aerospace vehicle's position with respect to the Earth comprises:
(i) having the aerospace vehicle acquire, at a time from Evening Civil Twilight to Morning Civil Twilight, an image of the Earth comprising at least one terrestrial light feature;
(ii) matching said at least one terrestrial light feature of the image with at least one feature of a terrestrial light data base;
(iii) weighting said matched images;
(iv) optionally, calculating a propagated position for said aerospace vehicle and checking the result of said propagated position against the weighting;
(v) using the time and the altitude that said image was taken to convert said weighted match into inertial coordinates;
(vi) optionally updating said aerospace vehicle's propagated position by using the inertial coordinates in a propagation position and/or an attitude calculation; and/or

b) determining the aerospace vehicle's pose estimation between two points in time comprises:
(i) having the aerospace vehicle acquire, at a time from Evening Civil Twilight to Morning Civil Twilight, at least two images of the Earth at different times, each of said at least two images containing at least one common terrestrial light feature;
(ii) comparing said at least two images to find the at least one common terrestrial light feature;
(iii) calculating the aerospace vehicle's pose as follows:
converting image coordinates of the at least two images that were acquired by a camera to normalized coordinates;
calculating an essential matrix from the normalized coordinates and then recovering the pose from the essential matrix; or
converting image coordinates of the at least two images that were acquired by a camera to normalized coordinates;
converting the normalized coordinates to pixel coordinates;
calculating a fundamental matrix from the pixel coordinates and then recovering the pose;

(iv) combining a known absolute position and attitude of the aerospace vehicle with the recovered pose to yield an updated attitude and estimated position for the aerospace vehicle.