Tightly coupled celestial-intertial navigation system

Patent metadata

Field	Value
Publication number	US-2016282123-A1
Application number	US-201514865709-A
Country	US
Kind code	A1
Filing date	Sep 25, 2015
Priority date	Mar 24, 2015
Publication date	Sep 29, 2016
Grant date	—

Abstract

One embodiment is directed towards a method of navigating a body. The method includes determining a respective measured direction of each of a plurality of celestial objects with respect to the body based on an output of one or more star tracking sensors mounted to the body. Calculating an expected direction of at least one of the plurality of celestial objects with respect to the body based on a current navigation solution for the body. Calculating an updated navigation solution for the body based on the expected direction of the at least one celestial object, the measured direction of the plurality of celestial objects, and an output of one or more inertial sensors mounted to the body.

First claim

1 . A navigation system for a body comprising:
one or more star tracking sensors mounted to the body; one or more inertial sensors mounted to the body; one or more processing devices coupled to the one or more star tracking sensors and the one or more inertial sensors; one or more memory devices coupled to the one or more processing devices, the one or more memory devices including instructions which, when executed by the one or more processing devices, cause the one or more processing devices to:
determine a respective measured direction of each of a plurality of celestial objects with respect to the body based on an output of the one or more star tracking sensors;
calculate an expected direction of at least one of the plurality of celestial objects with respect to the body based on a current navigation solution for the body; and
calculate an updated navigation solution for the body based on the expected direction of the at least one celestial object, the respective measured directions of the plurality of celestial objects, and an output of the one or more inertial sensors.

2 . The navigation system of claim 1 , wherein the instructions cause the one or more processing devices to use the expected direction of the at least one celestial object to aid in determining the measured direction for the at least one celestial object.

3 . The navigation system of claim 2 , wherein use the expected direction of the at least one celestial object includes steer at least one of the one or more star tracking sensors based on the expected direction such that the expected direction is within the field of view of the at least one star tracking sensor.

4 . The navigation system of claim 2 , wherein use the expected direction of the at least one celestial object includes windowing an output of the one or more star tracking sensors based on the expected direction.

5 . The navigation system of claim 1 , wherein the instructions cause the one or more processing devices to select the plurality of celestial objects from a larger number of celestial objects in order to optimize the navigation accuracy that can be obtained from the resulting direction measurements.

6 . The navigation system of claim 1 , wherein the current navigation solution is a navigation solution determined by the navigation system for a previous time step.

7 . The navigation system of claim 1 , wherein the instructions cause the one or more processing devices to calculate an error in a measured direction of the at least one celestial object caused by one or more of atmospheric effects or stellar aberration on the light from the celestial object; and adjust the measured direction for the at least one celestial object based on the error.

8 . The navigation system of claim 1 , wherein each of the plurality of celestial objects includes one of a star, planet, Earth satellite, or moon.

9 . A method of navigating a body, the method comprising:
determining a respective measured direction of each of a plurality of celestial objects with respect to the body based on an output of one or more star tracking sensors mounted to the body; calculating an expected direction of at least one of the plurality of celestial objects with respect to the body based on a current navigation solution for the body; and calculating an updated navigation solution for the body based on the expected direction of the at least one celestial object, the measured direction of the plurality of celestial objects, and an output of one or more inertial sensors mounted to the body.

10 . The method of claim 9 , comprising using the expected direction of the at least one celestial object to aid in determining the measured direction of the at least one celestial object.

11 . The method of claim 10 , wherein using the expected direction of the at least one celestial object includes steering at least one of the one or more star tracking sensors based on the expected direction such that the expected direction is within the field of view of the at least one star tracking sensor.

12 . The method of claim 10 , wherein using the expected direction of the at least one celestial object includes windowing an output of the one or more star tracking sensors based on the expected direction.

13 . The method of claim 9 , comprising selecting a plurality of celestial objects in which to measure the direction of, wherein the plurality of celestial objects are selected in order to optimize the navigation accuracy that can be obtained from the resulting direction measurements.

14 . The method of claim 9 , wherein the current navigation solution is a navigation solution determined by the navigation system for a previous time step.

15 . The method of claim 9 , comprising calculating an error in a measured direction of the at least one celestial object caused by one or more of atmospheric effects or stellar aberration on the light from the celestial object; and adjusting the measure direction based on the error.

16 . The method of claim 9 , wherein each of the plurality of celestial objects includes one of a star, planet, Earth satellite, or moon.

17 . A non-transitory processor-readable medium having processor-executable instructions stored thereon which, when executed by one or more processing devices, cause the one or more processing devices to:
determine a measured direction of each of a plurality of celestial objects with respect to the body based on an output of one or more star tracking sensors mounted to the body; calculate an expected direction of at least one of the plurality of celestial objects with respect to the body based on a current navigation solution for the body; and calculate an updated navigation solution for the body based on the expected direction of the at least one celestial object, the measured direction of the plurality of celestial objects, and an output of one or more inertial sensors mounted to the body.

18 . The non-transitory processor-readable medium of claim 17 , wherein the instructions are configured to steer at least one of the one or more star tracking sensors based on the expected direction such that the expected direction is within the field of view of the at least one star tracking sensor.

19 . The non-transitory processor-readable medium of claim 17 , wherein the instructions are configured to window an output of the one or more star tracking sensors based on the expected direction.

20 . The non-transitory processor-readable medium of claim 17 , wherein the instructions are configured to calculate an error in a measured direction of the at least one celestial object caused by atmospheric effects or stellar aberration on the light from the celestial object; and adjust the measure direction based on the errors.

Assignees

• Honeywell Int Inc

Inventors

• Mccroskey Robert C
• Hawkinson Wesley J
• Sanders Steven J
• Vallot Lawrence Charles

Classifications

• G01C21/005

  with correlation of navigation data from several sources, e.g. map or contour matching (G01C21/30 takes precedence) · CPC title

• B64G1/36

  using sensors, e.g. sun-sensors, horizon sensors · CPC title

• G01C21/025

  with the use of startrackers · CPC title

• B64G1/361

  using star sensors · CPC title

• G01C21/1656 Primary

  with passive imaging devices, e.g. cameras · CPC title