Spherical occulter coronagraph cubesat

Patent metadata

Field	Value
Publication number	US-9921099-B1
Application number	US-201615254323-A
Country	US
Kind code	B1
Filing date	Sep 1, 2016
Priority date	Sep 1, 2016
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

The present invention relates to a space-based instrument which provides continuous coronal electron temperature and velocity images, for a predetermined period of time, thereby improving the understanding of coronal evolution and how the solar wind and Coronal Mass Ejection transients evolve from the low solar atmosphere through the heliosphere for an entire solar rotation. Specifically, the present invention relates to using a 6U spherical occulter coronagraph CubeSat, and a relative navigational system (RNS) that controls the position of the spacecraft relative to the occulting sphere. The present invention innovatively deploys a free-flying spherical occulter, and after deployment, the actively controlled CubeSat will provide an inertial formation flying with the spherical occulter and Sun.

First claim

What is claimed is:

1. An occulter coronagraph CubeSat comprising:
a spherical occulter;
an occulter release mechanism;
wherein said spherical occulter is deployed from an occulter guide tube disposed in a body of said occulter coronagraph CubeSat, using said occulter release mechanism.

2. The occulter coronagraph CubeSat of claim 1 , wherein said spherical occulter is coated with a black paint material which provides greater than 90% absorption of any scattered light, and is a conductive surface which provides forward scatter suppression around said spherical occulter.

3. The occulter coronagraph CubeSat of claim 1 , further comprising:
a relative navigation system comprising a plurality of photodiodes, including first lateral photodiodes, second lateral photodiodes, full-sun photodiodes, and range photodiodes, said plurality of photodiodes which sense a translation and range of said spherical occulter to control a position of the CubeSat relative to said spherical occulter, and for formation flying feedback of a plurality of CubeSats.

4. The occulter coronagraph CubeSat of claim 3 , wherein said full-sun photodiodes are disposed on outer edges of a front face of the CubeSat, and are used to determine a full Sun intensity and allow for relative measurements of said plurality of photodiodes in the CubeSat;
wherein said first lateral photodiodes are disposed a predetermined distance from an aperture lens of said spherical occulter, and are used for lateral motion sensing;
wherein said range photodiodes are used for range measurement and are disposed at predetermined distances from said aperture lens;
wherein said second lateral photodiodes are disposed at a bottom of said occulter guide tube proximate to said occulter release mechanism, and detect lateral movement of said spherical occulter during release, to confirm that said spherical occulter has left said occulter guide tube.

5. The occulter coronagraph CubeSat of claim 3 , wherein said spherical occulter is a formation flying, passive, free-flying occulter, which reduces forward scattering noise contributed by diffraction around said spherical occulter at an inner half-angle field-of-view (FOV) of 0.375°, corresponding to 1.5 R Sun .

6. The occulter coronagraph CubeSat of claim 4 , wherein a size of said spherical occulter and said occulter release mechanism is maximized to an 8 cm diameter to fit into a 1 U unit allocation.

7. The occulter coronagraph CubeSat of claim 6 , wherein the occulter coronagraph CubeSat measures an electron temperature and a bulk electron vector velocity of the Sun's corona during one full Carrington rotation.

8. The occulter coronagraph CubeSat of claim 7 , wherein the occulter coronagraph CubeSat utilizes a heliocentric orbit.

9. The occulter coronagraph CubeSat of claim 8 , further comprising:
a de-tumble or sun finding mode; and
an occulter deployment model;
wherein said de-tumble or sun finding mode arrests a tipoff rotation rate, and a plurality of course sensors are used to find the Sun and reorient the occulter coronagraph CubeSat to point said front face to the Sun; and
wherein said occulter deployment mode utilizes said occulter release mechanism to deploy said spherical occulter.

10. The occulter coronagraph CubeSat of claim 9 , further comprising:
a science mode which points said spherical occulter at <0.5 deg with respect to the Sun, and a jitter of less than 18″ of jitter over a 9-sec integration;
wherein said spherical occulter always occludes the Sun based on a relative position between said spherical occulter and the occulter coronagraph CubeSat.

11. The occulter coronagraph CubeSat of claim 10 , further comprising:
a plurality of micro-cathode vacuum arc thrusters which are used for in-space micro-propulsion;
wherein said thrusters are fired for a prescribed burn after said spherical occulter is deployed, in order to move the occulter coronagraph CubeSat away from said spherical occulter; and
wherein on condition that said spherical occulter has successfully cleared the occulter coronagraph CubeSat, the thrusters are fired to translate the occulter coronagraph CubeSat so that said spherical occulter covers said aperture lens to occult the Sun, and to move the occulter coronagraph CubeSat further from said spherical occulter along an optical axis.

12. The occulter coronagraph CubeSat of claim 11 , wherein the occulter coronagraph CubeSat thrusts away from said spherical occulter with a force of about 1 micro-N.

13. A method of occulting a corona of the Sun, comprising:
deploying an occulter coronagraph CubeSat in a heliocentric orbit;
wherein said occulter coronagraph CubeSat comprises a spherical occulter, which is deployed from an occulter guide tube disposed in a body of said occulter coronagraph CubeSat utilizing an occulter release mechanism.

14. The method of claim 13 , wherein said spherical occulter is a formation flying, passive, free-flying occulter.

15. The method of claim 14 , wherein said spherical occulter is coated with a black paint material which provides better than 90% absorption of any scattered light as well as being a conductive surface which provides forward scatter suppression around said spherical occulter.

16. The method of claim 15 , wherein said spherical occulter reduces forward scattering noise contributed by diffraction around said spherical occulter at an inner half-angle field-of-view (FOV) of 0.375°, corresponding to 1.5 R Sun .

17. The method of claim 16 , wherein a size of said spherical occulter and said occulter release mechanism is maximized to an 8 cm diameter to fit into a 1 U unit allocation.

18. The method of claim 17 , wherein said occulter coronagraph CubeSat measures an electron temperature and a bulk electron vector velocity of the Sun's corona during one full Carrington rotation.

19. The method of claim 18 , wherein said occulter coronagraph CubeSat includes a de-tumble or sun finding mode; an occulter deployment mode, and a science mode;
wherein said de-tumble or sun finding mode arrests a tipoff rotation rate, and a plurality of course sensors are used to find the Sun and reorient said occulter coronagraph CubeSat to point said front face to the Sun;
wherein said occulter deployment mode utilizes said occulter release mechanism to deploy said spherical occulter;
wherein said science mode includes pointing said spherical occulter at <0.5 deg with respect to the Sun, and a jitter of less than 18″ of jitter over a 9-sec integration, and said spherical occulter always occludes the Sun based on a relative position between said spherical occulter and said occulter coronagraph CubeSat.

20. The method of claim 19 , further comprising:
utilizing a plurality of micro-cathode vacuum arc thrusters for in-space micro-propulsion;
wherein said thrusters are fired for a prescribed burn after said spherical occulter is deployed, in order to move said occulter coronagraph CubeSat away from said spherical occulter;
wherein on condition that said spherical occulter has successfully cleared said occulter coronagraph CubeSat, said thrusters are fired to first translate the occulter coronagraph CubeSat so that said spherical occulter covers said aperture lens to occult the Sun, and to move the occulter coronagraph CubeSat further from said spherical occulter along an optical axis; and
wherein said occulter coronagraph CubeSat thrusts away from said spherical occulter with a force of about 1 micro-N.

Assignees

• Nasa

Inventors

• Davila Joseph M
• Rabin Douglas M
• Reginald Nelson
• Gong Qian
• Shah Neerav
• Chamberlin Phillip C

Classifications

• G01J1/0266

  Field-of-view determination; Aiming or pointing of a photometer; Adjusting alignment; Encoding angular position; Size of the measurement area; Position tracking; Photodetection involving different fields of view for a single detector · CPC title

• B64G1/105

  Space science · CPC title

• B64G1/66

  Arrangements or adaptations of apparatus or instruments, not otherwise provided for · CPC title

• G01J1/0437 Primary

  using masks, aperture plates, spatial light modulators, spatial filters, e.g. reflective filters · CPC title

• G01S3/7861

  Solar tracking systems · CPC title