Sensor shift for remote sensing
Techniques for improving the quality of images captured by a remote sensing overhead platform such as a satellite. Sensor shifting is employed in an open-loop fashion to compensate for relative motion of the remote sensing overhead platform to the Earth. Control signals are generated for the sensor shift mechanism by an orbital motion compensation calculation that uses the predicted ephemeris (including orbit dynamics) and image geometry (overhead platform to target). Optionally, the calculation may use attitude and rate errors that are determined from on-board sensors.
1. A remote sensing platform for imaging an area spaced apart from the remote sensing platform, the remote sensing platform comprising:
a remote sensing platform body;
an image sensor positioned on the remote sensing platform body and that moves in a first plane relative to the remote sensing platform body and including relative to movement of the remote sensing platform body, wherein the first plane is an x-y plane and the movement of the image sensor within the first plane is in response to and controlled by control signals;
a controller that provides the control signals for movement of the image sensor relative to the remote sensing platform body, the control signals being based on movement of the remote sensing platform body relative to the area to be imaged, wherein, during image capture, the image sensor is movable by the control signals in the first plane relative to the remote sensing platform body and thereby including relative to movement of the remote sensing platform body in each one of and in any combination of along a straight line within the first plane, along a curved line within the first plane, and a rotational movement within the first plane;
wherein the image sensor is an area array image sensor having a quantity of rows of pixels that is at least one-tenth of a quantity of pixels in each row of pixels; and
wherein the controller is configured to move the image sensor through a sequence of positions within the first plane such that the image sensor captures an image of the same area in each of the positions.
2. The remote sensing platform of claim 1 , wherein the remote sensing platform is an orbital satellite.
3. The remote sensing platform of claim 1 , wherein calculation of the control signals is entirely free of being based on image correlation.
4. The remote sensing platform of claim 1 , wherein calculation of the control signals is entirely free of being based on any captured image.
5. The remote sensing platform of claim 1 , wherein the image sensor captures image data, and wherein the control signals are further based on a predicted orbital motion of the remote sensing platform body and the location of the captured image data relative to the remote sensing platform.
6. The remote sensing platform of claim 1 , wherein the image sensor moves so as to compensate for motion of the remote sensing platform relative to the area to be imaged for at least 15 milliseconds.
7. The remote sensing platform of claim 1 , wherein the movement of the image sensor along the curved line within the first plane compensates for at least one of off-nadir imaging or attitude error.
8. The remote sensing platform of claim 1 , further comprising at least one location sensor that detects location data corresponding to at least one of a position or orientation of the remote sensing platform body, wherein the control signals are further based on the location data.
9. The remote sensing platform of claim 8 , wherein the at least one location sensor includes a gyroscope and a GPS sensor.
10. The remote sensing platform of claim 8 , further comprising a star tracker that detects star data corresponding to a location of the remote sensing platform relative to at least one star, wherein the control signals are further based on the star data.
11. A method for imaging an area spaced apart from a remote sensing platform, the method comprising:
calculating, by a controller, a desirable movement pattern of an image sensor of the remote sensing platform relative to the area to be imaged based on movement of the remote sensing platform relative to the area to be imaged, the desirable movement pattern corresponding to the image sensor being movable during image capture and in a first plane relative to a remote sensing platform body and including relative to movement of the remote sensing platform body, wherein the first plane is an x-y plane and the image sensor is movable within the first plane in each one of and in any combination of along a straight line within the first plane, along a curved line within the first plane, and a rotational movement within the first plane;
controlling, by the controller, the image sensor to move along the desirable movement pattern within the first plane;
wherein the image sensor is an area array image sensor having a quantity of rows of pixels that is at least one-tenth of a quantity of pixels in each row of pixels; and
wherein the controlling comprises moving the image sensor through a sequence of positions within the first plane such that the image sensor captures an image of the same area in each of the positions.
12. The method of claim 11 , wherein the remote sensing platform is an orbital satellite.
13. The method of claim 11 , wherein calculating the desirable movement pattern is entirely free of being based on image correlation and is entirely free of being based on any captured image.
14. The method of claim 11 , wherein calculating the desirable movement pattern is further based on a predicted orbital motion of the remote sensing platform.
15. The method of claim 14 , wherein calculating the desirable movement pattern is further based on a location of image data captured by the image sensor relative to the remote sensing platform.