Star Tracker
First Claim
1. A method for determining a direction to a source of unpolarized electromagnetic radiation, the method comprising:
- exposing a first sensor to the unpolarized electromagnetic radiation, the first sensor being primarily sensitive to electromagnetic radiation polarized along a first axis and configured to generate a first signal proportional to a magnitude of the unpolarized electromagnetic radiation detected by the first sensor;
exposing a second sensor to the unpolarized electromagnetic radiation, the second sensor being primarily sensitive to electromagnetic radiation polarized along a second axis, different than the first axis, and configured to generate a second signal proportional to a magnitude of the unpolarized electromagnetic radiation detected by the second sensor;
determining a ratio of the first signal to the second signal; and
using the ratio to calculate an angle of incidence of the unpolarized electromagnetic radiation.
1 Assignment
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Accused Products
Abstract
A star tracker determines a location or orientation of an object, such as a space vehicle, by observing unpolarized light from one or more stars or other relatively bright navigational marks, without imaging optics, pixelated imaging sensors or associated pixel readout electronics. An angle of incidence of the light is determined by comparing signals from two or more differently polarized optical sensors. The star tracker may be fabricated on a thin substrate. Some embodiments have vertical profiles of essentially just their optical sensors. Some embodiments include micro-baffles to limit field of view of the optical sensors.
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Citations
21 Claims
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1. A method for determining a direction to a source of unpolarized electromagnetic radiation, the method comprising:
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exposing a first sensor to the unpolarized electromagnetic radiation, the first sensor being primarily sensitive to electromagnetic radiation polarized along a first axis and configured to generate a first signal proportional to a magnitude of the unpolarized electromagnetic radiation detected by the first sensor; exposing a second sensor to the unpolarized electromagnetic radiation, the second sensor being primarily sensitive to electromagnetic radiation polarized along a second axis, different than the first axis, and configured to generate a second signal proportional to a magnitude of the unpolarized electromagnetic radiation detected by the second sensor; determining a ratio of the first signal to the second signal; and using the ratio to calculate an angle of incidence of the unpolarized electromagnetic radiation. - View Dependent Claims (5, 6, 7, 8, 9)
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2. A method according to claim 2, wherein exposing the first and second sensors to the unpolarized electromagnetic radiation comprises exposing the first and second sensors to unpolarized electromagnetic radiation from a star.
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3. A method according to claim 3, further comprising:
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automatically accessing a database that stores a star catalog; and automatically calculating a location in space based at least in part on the angle of incidence and information in the star catalog. - View Dependent Claims (4)
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10. A star tracker for determining a direction to a source of unpolarized electromagnetic radiation, the star tracker comprising:
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a plurality of electromagnetic radiation sensors, wherein each sensor of the plurality of electromagnetic radiation sensors is primarily sensitive to electromagnetic radiation polarized along a different axis and generates a proportional signal in proportion to a magnitude of unpolarized electromagnetic radiation detected by the sensor; a ratio detector that receives the proportional signals generated by the plurality of electromagnetic radiation sensors and generates a ratio signal that represents a ratio of at least two of the proportional signals; and an angle of incidence calculator that receives the ratio signal and generates therefrom a signal representing an angle of incidence of the unpolarized electromagnetic radiation. - View Dependent Claims (11, 12, 13, 14)
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15. A computer program product for determining a direction to a source of unpolarized electromagnetic radiation, the computer program product comprising a non-transitory computer-readable medium having computer readable program code stored thereon, the computer readable program code, when executed by a processor, causes the processor to:
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receive a first signal from a first sensor exposed to the unpolarized electromagnetic radiation, the first sensor being primarily sensitive to electromagnetic radiation polarized along a first axis and configured to generate the first signal proportional to a magnitude of the unpolarized electromagnetic radiation detected by the first sensor; receive a second signal from a second sensor exposed to the unpolarized electromagnetic radiation, the second sensor being primarily sensitive to electromagnetic radiation polarized along a second axis, different than the first axis, and configured to generate the second signal proportional to a magnitude of the unpolarized electromagnetic radiation detected by the second sensor; determine a ratio of the first signal to the second signal; and use the ratio to calculate an angle of incidence of the unpolarized electromagnetic radiation. - View Dependent Claims (16, 17, 18, 19)
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20. A star tracker for determining a direction to a source of unpolarized electromagnetic radiation, the star tracker comprising:
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a first electromagnetic radiation sensor configured to generate a first signal proportional to a first polarization component of unpolarized electromagnetic radiation impinging on the first electromagnetic radiation sensor; a second electromagnetic radiation sensor configured to generate a second signal proportional to a second polarization component of unpolarized electromagnetic radiation impinging on the second electromagnetic radiation sensor, the second polarization component being oriented differently than the first polarization component; a ratio detector that receives the first and second signals and generates a ratio signal that represents a ratio of the first signal to the second signal; and an angle of incidence calculator that receives the ratio signal and generates therefrom a signal representing an angle of incidence of the unpolarized electromagnetic radiation.
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21. A star tracker, comprising:
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a plurality of electromagnetic radiation sensors, each sensor of the plurality of electromagnetic radiation sensors configured to generate a respective signal in proportion to magnitude of a different polarization component of unpolarized electromagnetic radiation impinging on the sensor; and a ratio detector configured to receive the signals generated by the plurality of electromagnetic radiation sensors and calculate an angle of incidence of the unpolarized electromagnetic radiation.
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Specification