Optical problem concerning space mirror.

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Discussion Overview

The discussion revolves around the challenges of designing a space-based energy satellite that utilizes a mirror to reflect sunlight to a photovoltaic ground station on Earth. Participants explore the optical difficulties associated with varying angles of sunlight from different solar poles and the implications for image size on the ground.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes the challenge of using a mirror to reflect sunlight due to the varying angles at which light strikes the mirror, resulting in a large illuminated area on Earth.
  • Another participant suggests using a concave mirror as a potential solution, implying it could help focus the sunlight.
  • A later reply questions the effectiveness of a concave mirror, stating that it cannot achieve the desired small image size due to the variety of angles at which light hits the mirror.
  • Another participant acknowledges that the issue of varying angles is a common challenge with any lens or mirror attempting to create an image of a finite object, noting additional constraints related to mirror-image distance and focal length.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness of using a concave mirror, with some suggesting it as a solution while others argue it does not adequately address the problem of varying light angles. The discussion remains unresolved regarding the best approach to achieve a smaller image size on the ground.

Contextual Notes

The discussion highlights limitations related to the constraints of mirror-image distance and the nature of light reflection, which may affect the feasibility of proposed solutions.

fatjohn
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When designing a space based energy satellite for our project, we ran across the option to just use a mirror to reflect extra light to a photovoltaic ground station on earth. The main difficulty of this option is that due to the fact that the light coming from the south pole of the sun hits the mirror with a different angle then the light coming from the north pole a 336 kilometer wide circle on Earth would be illuminated.
Is there any way to overcome this problem either with a configuration of lenses or with certain metamaterials or nanomaterials? It seems to me that at a certain (focal) point on the mirror light hits it in a various different angles. This is a problem that to my knowledge cannot be overcome with macro devices. Anybody has a proposition?

Thank you for your attention.
 
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fatjohn said:
Is there any way to overcome this problem either with a configuration of lenses or with certain metamaterials or nanomaterials?
Or you could just use a concave mirror
You are trying to make an image of the sun on the ground
 
mgb_phys said:
Or you could just use a concave mirror
You are trying to make an image of the sun on the ground

Yes I am trying to make an image of the sun on the ground but i am trying to make that image as small as possible. A concave mirror cannot do the job this is because at one point of the mirror the light comes in at a variaty of angles.
 
That is true of any lens or mirror making an image of a finite object.

You have an extra constraint that the mirror-image distance (and so focal length) is restricted which sets the minimum size of the image.
 

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