Star sightings by satellite for image navigation

A system for performing image navigation of a camera on board a satellite, said system comprising:

• a three-axis stabilized satellite orbiting a celestial body;
• at least a first camera on board the satellite for gathering data from scenes of the celestial body;
• means for commanding an optical component of the camera to slew in two orthogonal dimensions to detect stars just beyond the limb of the celestial body;
• coupled to the camera, means for processing signals produced by the camera in response to star detection, to generate measured star locations;
• and
• coupled to the processing means, means for feeding the measured star locations to an image navigation computer;
• wherein the system further comprises a second camera;
• the first and second cameras independently detect stars;
• and
• information determined by said star detection is used by the processing means and computer to independently determine the attitude of each camera.

A system for performing image navigation of a camera on board a satellite, said system comprising:

• a three-axis stabilized satellite orbiting a celestial body;
• at least a first camera on board the satellite for gathering data from scenes of the celestial body;
• means for commanding an optical component of the camera to slew in two orthogonal dimensions to detect stars just beyond the limb of the celestial body;
• coupled to the camera, means for processing signals produced by the camera in response to star detection, to generate measured star locations;
• and
• coupled to the processing means, means for feeding the measured star locations to an image navigation computer;
• wherein:
• the commanding means expands the effective star-seeking field of view of the optical component in a first dimension by commanding the optical component to seek more stars than for normal on-orbit operations;
• and
• the commanding means expands the field of view of the optical component in a second dimension, orthogonal to the first, by increasing the star-seeking commanded dwell time of the optical component compared with normal on-orbit operations.