An HDST would need to be at least 10 metres across to be able to spy on the atmospheres of dozens of exoplanets — the number needed to establish decent statistics on whether life is common in the Universe, Postman says. The telescope’s upper size limit of 12 metres is dictated by how much weight a feasible rocket system could launch into space.
Overall the HDST would be "100 to 1,000 times as powerful as Hubble." That number comes from combining multiple factors of HDST as they compare with Hubble, including "25 to 35 times the collecting area," or surface area of the telescope (the aperture squared), and four times the area of coverage. AURA's plan for the HDST would place it in a region known as the second Lagrangian point (L2), about 932,000 miles (1.5 million kilometers) from Earth, which would give it a clearer and darker sky than the Earth-orbiting Hubble, reducing background noise from image
It would cost US$10 billion or more. However, it would allow imaging like we are getting from a closeup of Pluto on regular basis for years all around the solar system and beyond to other stars and exoplanets. We should also develop arrays of many space telescopes to create hypertelescopes with even better resolution and kilometer sized telescopes on the moon.
• A 10-12 meter aperture UVOIR space telescope, with resolution of 100 pc everywhere in the visible universe
• Equipped with a coronagraph for direct imaging of exoplanets, for discovery and characterization of tens of exoEarths
A feasible, streamlined concept with:
– A segmented, deployable mirror in a warm telescope
– Diffraction-limited performance at visible wavelengths
– Full complement of coronagraphic, imaging, and spectroscopic instruments
– Covering UV to near-IR wavelengths
– Photon-counting detectors in gigapixel arrays
• Most key HDST technologies are already being developed, under NASA COR and ExEP Programs, WFIRST/AFTA, JWST, and other sources
• Most of the highest HDST technical risks will be retired by successful completion of these projects, especially the WFIRST/AFTA Coronagraph – a technology precursor for HDST
• An HDST can be credibly proposed to the 2020 Decadal Survey for start in the mid to late 2020s, with some additional study, starting now
• These HDST-specific studies should build incrementally on current activities, to exploit the current rapid progress while keeping costs low
SOURCES - NASA, Nature