Multi-functional star tracker with precision focal plane position control for small cubesat-class satellites

A method of operating an optical system in an Earth-orbiting satellite, the optical system including a plurality of optical sensors arranged on a focal plane and configured to generate an image, optics having a reference axis therethrough and configured and arranged to focus incident light onto the plurality of optical sensors, and a piezoelectric stage actuator coupled to the plurality of optical sensors and configured to translate the plurality of optical sensors in at least two axes each orthogonal to the reference axis, the method comprising:

• detecting at least three guide stars and a target star within the image;
• estimating an attitude of the satellite from positions of the at least three guide stars on the basis of a guide star database;
• stabilizing, within a coarse threshold, the attitude of the satellite with respect to a desired attitude by commanding changes to the attitude of the satellite based on a difference between the estimated attitude and the desired attitude;
• estimating an angular rate of the focal plane from rates of the positions of the at least three guide stars;
• estimating a position error of the target star based on the angular rate of the focal plane;
• and
• stabilizing, within a fine threshold that is smaller than the coarse threshold, a position of the target star with respect to one of the plurality of optical sensors by adjusting a position of the plurality of optical sensors with respect to the reference axis based on the estimated position error of the target star.

An optical system for use in an Earth-orbiting satellite, comprising:

• a plurality of optical sensors;
• optics having a reference axis therethrough and configured to focus incident light onto the plurality of optical sensors;
• an actuator coupled to the plurality of optical sensors and configured to translate the plurality of optical sensors in at least two axes each orthogonal to the reference axis;
• and
• means coupled to the plurality of optical sensors and the actuator for independently stabilizing, using images generated by the plurality of optical sensors, an attitude of the satellite and a position of the plurality of optical sensors with respect to a target star.