Methods and apparatus for deployable sparse-aperture telescopes
An imaging system includes a metering structure and a plurality of foldable members disposed around a periphery of the metering structure. Each foldable member in the plurality of foldable members includes an arm comprising a strain deployable composite and a reflector disposed on the arm. The arm in a respective foldable member in the plurality of foldable members is configured to hold the respective foldable member toward the metering structure in a first state and to hold the respective foldable member away from the metering structure in a second state such that the reflector of the respective foldable member forms part of a sparse aperture in the second state.
1. An imaging system comprising:
a metering structure; and
a plurality of foldable members disposed around a periphery of the metering structure, each foldable member in the plurality of foldable members comprising:
an arm comprising a strain deployable composite; and
a reflector disposed on the arm,
wherein the arm in a respective foldable member in the plurality of foldable members is configured to hold the respective foldable member toward the metering structure in a first state and to hold the respective foldable member away from the metering structure in a second state such that the reflector of the respective foldable member forms part of a sparse aperture in the second state,
wherein the arm is attached directly to the metering structure, and
wherein the arm has a first end and a second end and is bent at a point between the first end and the second end in the first state and unbends when transitioning from the first state to the second state.
2. The imaging system of claim 1 , wherein each foldable member further comprises an actuator, operably coupled to the reflector, to align the reflector.
3. The imaging system of claim 2 , wherein the actuator is configured to align the reflector in three dimensions.
4. The imaging system of claim 1 , wherein the strain deployable composite comprises at least one of fiberglass or a carbon fiber composite.
5. The imaging system of claim 1 , wherein the strain deployable composite is strained in the first state and unstrained in the second state.
6. The imaging system of claim 1 , wherein the arm in each foldable member comprises:
a first composite tape comprising the strain deployable composite;
a second composite tape comprising the strain deployable composite; and
a separator disposed between the first composite tape and the second composite tape such that the first composite tape and the second composite tape define at least a portion of a cavity.
7. The imaging system of claim 6 , wherein at least one of the first composite tape and the second composite tape defines at least a portion of a tubular structure.
8. The imaging system of claim 1 , further comprising:
a detector; and
a secondary optic, in optical communication with the detector and the sparse aperture, to direct light reflected by the sparse aperture toward the detector.
9. The imaging system of claim 8 , wherein the secondary optic has a hyperbolic surface with high-order aspherics.
10. The imaging system of claim 1 , wherein the plurality of foldable members comprises at least four foldable members disposed around the periphery of the metering structure.
11. The imaging system of claim 1 , wherein, in the second state, each reflector is within one micron of a desired position of the reflector within the sparse aperture.
12. The imaging system of claim 1 , wherein, in the second state, each reflector is within about λ/10 to about λ/2 of a desired position of the reflector within the sparse aperture, wherein λ is an operating wavelength of the imaging system.
13. The imaging system of claim 1 , wherein the sparse aperture defines a portion of a hyperboloid, a paraboloid, or a sphere.
14. The imaging system of claim 1 , wherein each reflector comprises a plurality of reflecting elements.
15. A method of deploying an imaging system, the imaging system comprising a plurality of foldable members disposed around a periphery of a metering structure, each foldable member in the plurality of foldable members attached directly to the metering structure and comprising a reflector disposed on an arm comprising a strain deployable composite, each arm having a first end and a second end, the method comprising:
A) stowing the plurality of foldable members so as to strain the strain deployable composite in each arm, the stowing comprising bending each arm at a point between the first end and the second end of the arm; and
B) releasing the strain on the strain deployable composite so as to deploy reflectors in the plurality of foldable members to form a sparse aperture, the releasing comprising allowing each arm to unbend.
16. The method of claim 15 , wherein A) comprises collapsing the plurality of foldable members towards the metering structure.
17. The method of claim 15 , wherein B) further comprises deploying the reflectors to form a sparse aperture.
18. The method of claim 15 , further comprising:
C) aligning at least one reflector in the plurality of foldable members with an actuator operably coupled to the at least one reflector.
19. The method of claim 18 , wherein C) comprises:
C1) sensing light reflected by the sparse aperture;
C2) determining a difference between an actual position of the at least one reflector and a desired position of the at least one reflector based at least in part on the sensing of the light in C1); and
C3) actuating the actuator so as to move the at least one reflector towards the desired position.
20. The method of claim 19 , wherein C1) comprises:
reflecting a portion of the light from the at least one reflector toward a secondary optic;
reflecting the portion of the light from the secondary optic to a detector so as to form at least a portion of an image; and
sensing the at least a portion of the image with a detector.
21. The method of claim 19 , wherein C3) comprises:
moving the at least one reflector to within λ/2 of the desired position, wherein λ is a wavelength of the light detected in C1).
22. An imaging system comprising:
a metering structure; and
a plurality of foldable members disposed around a periphery of the metering structure, each foldable member in the plurality of foldable members comprising a respective arm and a respective reflector disposed on the respective arm, wherein the respective arm comprises:
a first composite tape; and
a second composite tape disposed on the first composite tape so as to define at least partially a cavity between the first composite tape and the second composite tape,
wherein the first composite tape and the second composite tape comprise a fiberglass or a carbon fiber composite, and
wherein the arm in a respective foldable member in the plurality of foldable members is configured to hold the respective foldable member toward the metering structure in a first state and to hold the respective foldable member away from the metering structure in a second state such that the reflector of the respective foldable member forms part of a sparse aperture in the second state.
23. The imaging system of claim 1 , wherein the arm is bent close to the first end in the first state.
24. The imaging system of claim 1 , wherein the point is close to a midpoint between the first end and the second end in the first state.
25. The imaging system of claim 1 , wherein the arm stores strain energy in the first state and is deployed from the first state to the second state by releasing the strain energy.