Hybrid Observatory for Earth-like Exoplanets (HOEE)

The Hybrid Observatory for Earth-like Exoplanets (HOEE) was proposed to solve the main technical challenge of building an ultra-light starshade for the first hybrid exoplanet observatory. The HOEE combines an orbiting starshade with a large ground telescope, with fundamental advantages over competing technologies for imaging exoplanets. It converts the challenges of optical perfection in giant space telescopes, into mechanical engineering for a passive object that works with much larger telescopes already built and operating on the ground. It is perfectly efficient outside its inner working angle (angular size of its shadow), blocking no planet light. Once built to the required tolerance, its optical performance is guaranteed. There is no need for extreme precision or stability in any optical system.
Exoplanet science is the most rapidly growing area of astrophysics today and has been a key investment area for NASA ever since the HST and Beyond report of 1995 https://www.stsci.edu/stsci/org/hst-and-beyond-report.pdf. “Are we alone?” is posted prominently on NASA’s web sites, and is one of the most popular topics with the public and the press. The HOEE would address the highest priority recommendation of the Exoplanet Strategy report: observe reflected light from Earth-like planets with low-resolution spectroscopy. This light is influenced by surface minerals, oceans, continents, weather, vegetation, and atmospheric molecular constituents, temperature, and pressure. In particular it is influenced by the presence of water and oxygen, key indicators of an Earth-like planet, and evidence for the existence of life elsewhere. HOEE would help answer the questions: is the Solar System rare? Are there oxygen and water-rich atmospheres on potentially habitable planets? Is there life elsewhere? Does life require a special chance event, or is it a thermodynamic imperative, occurring wherever conditions are suitable?
Our Phase I NIAC study focused on the major challenges of this mission approach, identifying which methods are best suited to reduce mass while maintaining shape under the expected operational conditions. We refined our requirements, worked with the NASA Tournaments office to find new concepts through GrabCad.com, we sponsored a student competition through the Society of Physics Students, and we developed our own inflatable starshade concepts. We also collected information including an analysis of the JUL starshade concept extrapolated to the 100 m scale, we refined the optical tolerance analysis, and we formed a collaboration with the MIT-NASA Ames group developing a robotic assembly system with voxels (small unit cells). We completed a Kepner-Tregoe analysis of the current concepts and conclude that none of the concepts yet meet all requirements, but there are three main possibilities: an improved deployable design, an inflatable design, and a voxel design with robots. Kepner-Tregoe is a commercial enterprise and their methodology is widely applied in aerospace engineering. See https://kepner-tregoe.com/.