New lightweight telescope mirror can be packed and easily unfolded in space

After much trial and error, the institute's team was able to successfully create a prototype of a parabolic membrane mirror up to 12 inches (30 cm) in diameter. The versatility of this new mirror is due to its thin design (thinner than traditional mirrors) and high optical quality, which is required for sophisticated space telescopes. 

Creating the mirror membrane

It entailed a meticulous step-by-step process to create the perfect parabolic shape mirror — ideal for gathering cosmic light from distant objects in space.

The lightweight mirror membrane was created using a special chemical vapor deposition technique placed on a rotating liquid bowl inside a vacuum chamber.

In case of imperfections in the parabolic shape that may occur after the mirror is unpacked, the team developed a thermal method to get back the actual shape. According to the statement, the heat-based thermal method uses a localized temperature setting with light to achieve the perfect parabolic shape.

Through this unique technique, the mirrors could be easily scaled up to the sizes required for space telescopes. However, the team asserts that the prototype is only a starting point and that much more work is needed to make it suitable for deployment in space.

“Although this work only demonstrated the feasibility of the methods, it lays the groundwork for larger packable mirror systems that are less expensive. It could make lightweight mirrors that are 15 or 20 meters in diameter a reality, enabling space-based telescopes that are orders of magnitude more sensitive than ones currently deployed or being planned,” said Rabien. 

If this thin and lightweight mirror prototype is successful, it could revolutionize how we see and understand the cosmic universe.

After this study, the team plans to build a meter-sized deposition chamber in order to better understand "packaging unfolding processes for a large-scale primary mirror."

The results have been published in the journal Applied Optics.

Study Abstract:

A key element for the development of extremely large telescopes in space or balloon-borne observatories will be a reduction in the areal weight of the primary mirror. Large membrane mirrors offer a very low areal weight but are difficult to manufacture with the optical quality needed for astronomical telescopes. This paper demonstrates a practical method to overcome this limitation. In a test chamber we have successfully grown optical quality parabolic membrane mirrors on a rotating liquid in a test chamber. These polymer mirror prototypes of up to 30 cm in diameter show a sufficiently low surface roughness and can be coated with reflective layers. By manipulating the parabolic shape locally using radiative adaptive optics methods, it is shown that imperfections or changes in the shape can be corrected. With only tiny local temperature changes induced by the radiation, many micrometers of stroke have been achieved. Scaling the method investigated to produce mirrors with diameters of many meters is possible using available technology. This approach opens the possibility to produce affordable extremely large primary mirrors for space telescopes. With the flexibility of the membrane material, this type of mirror can be compactly rolled up when stored in the launch vehicle, and then be deployed in space.