Sparse Apertures for Next Generation Optical Space Telescopes

Technology Roadmap Sections and Deliverables

This technology roadmap is identified as follows:

• 2SASOT - Sparse Aperture Space Optical Telescope

This a Level 2 roadmap that evaluates sparse aperture optical telescopes that can achieve larger effective aperture. This feeds into a Level 1 roadmap for next generation space optical telescopes, which includes separate categories like monolithic or segmented telescopes. A Level 3 roadmap would describe the technological progress required to achieve a particular sparse aperture technique (deployable, formation flying, or erecting on-orbit). A Level 4 roadmap would describe individual enabling technologies such as on-orbit alignment metrology, and precision formation flying control algorithms.

Roadmap Overview

The angular resolution of a telescope is proportional to the size of the aperture. The mass and thus cost of space telescopes increases exponentially with aperture diameter. There is a need for systems that can produce the equivalent of a large aperture with low mass. This can be achieved by creating a synthetic aperture using multiple sub-apertures. One method to achieve this is to create a large number of small spacecraft, flying in a formation that creates the synthetic aperture.

Currently, a sparse aperture space telescope has not yet been fielded. In 2006, Lockheed Martin built a laboratory demonstration of a sparse aperture space telescope, which is depicted in the figure below. Currently, the technology appears be at approximately TRL 4. Research has proven the feasibility of the technology, however, significant technology development must be completed before a space technology demonstration is ready.

DSM Allocation

The design structure matrix for space optical telescopes is shown in the figure below. This DSM starts at Level 1.

From this top level DSM, we can extract a Level 2 DSM specifically for Sparse Aperture Space Optical Telescopes (SASOT), which is provided below. This matrix can also be view in tree form. Here we can easily see that there are several enabling technologies required to develop SASOTs that are common to all Level 3 instantiations (deployable, on-orbit assembly, formation flying). There are also some technologies that are only feed one Level 3 SASOT, so such as low cost sub-aperture small sats enabling formation flying sparse apertures. Finally, the DSM tree includes some lower level technologies there are also important, but do not have their own specific roadmap identifier at this time.

Roadmap OPM Model

An Object Process Model is presented for a formation-flight synthetic aperture imaging system.  

Figures of Merit

One key figure of merit is the mass-specific effective aperture. The figure below shows the progression of this figure of merit over time from early Earth-reconnaissance satellites, to the filled-aperture space telescopes in the past 30 years, to the next generation of synthetic aperture systems that extend the pareto front.