Electron-bombarded active pixel sensor star camera

Patent metadata

Field	Value
Publication number	US-9733087-B2
Application number	US-201414211308-A
Country	US
Kind code	B2
Filing date	Mar 14, 2014
Priority date	Mar 14, 2013
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

A star camera system that includes an optical system configured to focus radiation from a star to be imaged onto a collector. Specifically, the collector is in the form of an electron bombarded active pixel sensor (EBAPS) configured to provide high gain. The EBAPS comprising a photocathode disposed in a vacuum is configured to release electron into a vacuum when exposed to radiation focused thereon by the optical system. In addition, the EBAPS includes an active pixel sensor anode disposed distant from the photocathode in the vacuum. An electric field is generated by a voltage source to direct electrons from the photocathode to the active pixel sensor anode to thereby generate an image of the star.

First claim

The invention claimed is:

1. A star camera system, comprising:
an optical system configured to focus radiation from a star to be imaged onto a collector, the collector being in a form of an electron bombarded active pixel sensor configured to provide increased gain and being movable relative to a focal plane of the optical system, the collector including:
a photocathode disposed in a vacuum and configured to release electrons into a vacuum when exposed to radiation focused thereon by the optical system;
an active pixel sensor anode disposed separate from the photocathode in the vacuum; and
a voltage source configured to generate an electric field configured to direct the electrons from the photocathode to strike the active pixel sensor anode and generate an image of the star;

wherein movement of the collector, within the focal plane of the optical system, by an amount less than a pixel size of the collector results in generation of images having increased resolution.

2. The star camera system of claim 1 , wherein:
the optical system is configured to focus ultraviolet radiation from the star to be imaged onto the collector,
the electron bombarded active pixel sensor is an ultraviolet sensitive electron bombarded active pixel sensor, including:
an ultraviolet sensitive photocathode, wherein the electric field is generated between the ultraviolet sensitive photocathode and the active pixel sensor anode.

3. The star camera system of claim 2 , wherein the ultraviolet sensitive photocathode comprises gallium nitride.

4. The star camera system of claim 1 , wherein:
the optical system is configured to focus infrared radiation from the star to be imaged onto the collector,
the photocathode is an infrared sensitive photocathode, and
the electric field is generated between the infrared sensitive photocathode and the active pixel sensor anode.

5. The star camera system of claim 4 , wherein the electron bombarded active pixel sensor comprises a silicon germanium layer.

6. A method of capturing a star image for celestial navigation, orientation, position and attitude measurement, and solution correction, the method comprising:
in an optical system configured to focus radiation from a star to be imaged onto a collector in a form of an electron bombarded active pixel sensor:
projecting a star image onto a photocathode of the electron bombarded active pixel sensor disposed in a vacuum to release electrons in the vacuum;
positioning an active pixel sensor anode of the electron bombarded active pixel sensor separate from the photocathode in the vacuum;
outputting a signal from the active pixel sensor anode; and
generating images of high resolution by moving the collector, within a focal plane of the optical system, by an amount less than a pixel size of the collector to obtain multiple images of the star at various location.

7. The method of claim 6 , further comprising:
generating a voltage between the photocathode and the anode to direct the electrons from the photocathode to the anode, prior to outputting the signal from the active pixel sensor anode.

8. The method of claim 6 , wherein the photocathode is an ultraviolet sensitive photocathode.

9. The method of claim 8 , wherein the ultraviolet sensitive photocathode comprises gallium nitride.

10. The method of claim 6 , wherein:
the optical system is configured to focus infrared radiation from the star to be imaged onto the collector,
the photocathode is an infrared sensitive photocathode, and
the electric field is generated between the infrared sensitive photocathode and the active pixel sensor anode.

11. The star camera system of claim 10 , wherein the electron bombarded active pixel sensor comprises a silicon germanium layer.

12. A star camera system, comprising:
an optical system configured to focus infrared radiation from at least two stars onto a collector the collector in a form of an electron bombarded active pixel sensor configured to detect the radiation from the at least two stars focused thereon by the optical system and including:
an infrared sensitive photocathode disposed in a vacuum and configured to release electrons into the vacuum when exposed to infrared radiation focused thereon by the optical system;
an active pixel sensor anode disposed separate from the infrared sensitive photocathode in the vacuum;
a voltage source to generate an electric field between the infrared sensitive photocathode and the active pixel sensor anode configured to direct the electrons from the infrared sensitive photocathode to the active pixel sensor anode, thereby forming an electron image of the two stars on the active pixel sensor anode; and
a translation device to move the collector, within the focal plane of the optical system, by an amount less than a pixel size of the collector results in generation of images having increased resolution.

13. The star camera of claim 12 , wherein the electron bombarded active pixel sensor comprises a silicon germanium layer.

14. A method of capturing a star image for celestial navigation, comprising:
projecting at least two star images onto a collector in a form of an electron bombarded active pixel sensor, including:
an infrared sensitive photocathode in a vacuum configured to release electrons in the vacuum when exposed to infrared radiation focused thereon by an optical system;
an active pixel sensor anode separate from the infrared sensitive photocathode in the vacuum;
a voltage source to direct electrons from the infrared sensitive photocathode to the active pixel sensor anode;
outputting a signal from the active pixel sensor anode; and
generating images of high resolution by moving the collector, within a focal plane of the optical system, by an amount less than a pixel size of the collector to obtain multiple images of the star at various location.

15. The method of claim 14 , wherein the electron bombarded active pixel sensor comprises a silicon germanium layer.

Assignees

• Charles Stark Draper Laboratory Inc

Inventors

• Laine Juha-Pekka J
• Blasche Gregory
• Boyle John J
• Bohn Paul
• Dawson Robin M
• Lane Benjamin F
• Waldron Erik L
• Smith Stephen P

Classifications

• H01J31/507

  using a large number of channels, e.g. microchannel plates · CPC title

• G01C21/025 Primary

  with the use of startrackers · CPC title

• H04N5/30

  Transforming light or analogous information into electric information (scanning details H04N3/00; cameras or camera modules comprising electronic image sensors, or control thereof H04N23/00; circuitry of solid-state image sensors [SSIS] or control thereof H04N25/00) · CPC title

• H04N5/33

  Transforming infrared radiation (cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20) · CPC title

• H04N23/20

  for generating image signals from infrared radiation only · CPC title