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Mega Telescopes of the 21st Century Evolution in the Ground-Space Synergy Dr. Marc Postman (STScI) & Richard Ellis (Caltech) Concept for 30m Ground-based Telescope (TMT) James Webb Space Telescope (6.5m telescope) Primary Telescope Aperture vs Time 1400 TMT Primary Aperture (inches) 1200 1000 800 600 Keck 400 200 Galileo Newton 0 1500 1550 1600 1650 1700 1750 1800 Year 1850 1900 1950 2000 2050 1010 Slide courtesy of J. Gardner 1600 1700 1800 1900 Year of observations Big Telescopes with Sensitive Detectors in Space (but also on the ground) Mount Palomar 200” Soviet 6-m Rosse’s 72” 1610 Short’s 21.5” 1665 Mount Wilson 100” 1926 Herschell’s 48” Adapted from Cosmic Discovery, M. Harwit 1796 Galileo 102 Photography Sensitivity 106 Improvement over the Eye 104 CCDs Telescopes alone Huygens eyepiece Slow f ratios 108 Photographic & electronic detection HST JWST How to win at Astronomy 2000 8m Ground (0.4 arcsec) HST (0.1 arcsec) D.L. 30m Telescope (0.008 arcsec) How a galaxy at a redshift of ~1 (7 billion l.y. away) would appear … NASA’s Great Observatories ~$2.5B investment in 8-10m telescopes Synergistic attributes: Space: unique wavelengths, angular resolution limited primarily by the size of telescope, very much reduced IR background, single telescope can see the entire sky Ground: spectroscopy of very faint objects, panoramic fields, upgradable technologies Large Ground-based Telescope Design Concepts Giant Magellan Telescope Seven 8.4m monolithic mirrors Total Effective Diameter: ~22m Shown to same relative scale Giant Segmented Mirror Telescope (aka TMT) 738 1.2m segments Total Effective Diameter: 30m Adaptive Optics: “Eye Glasses” for Ground-based Telescopes QuickTime™ and a H.263 decompressor are needed to see this picture. Computer driven actuators alter the shape of a “Deformable” Mirror to compensate for the atmospheric distortions. The mirror is a small mirror placed near the focal point of the telescope and thus the distortions can be made rapidly and across many points. Credit: Clip from European Southern Observatory Press Release Performance of Keck NGS AO System: Miranda+Uranus Neptune Courtesy: Wizinowich & Keck AO team Same objects with Hubble: Titan But AO has its Limits… • Space provides unique access to UV, x-rays • Space provides very stable environment where image resolution is limited primarily by the size of the telescope. • NIR sky background vastly lower in space Sky from Mauna Kea Sky from JWST The James Webb Space Telescope • JWST will be – 36x faster than HST – 2000x faster than Spitzer • JWST will have an overwhelming advantage for imaging at wavelengths > 2 microns and for spectroscopy at wavelengths longer than 3 microns • TMT will rule below 2 microns but ... Together, JWST and TMT should continue the type of scientific breakthroughs made possible by HST and the current 8-10m ground-based telescopes Impact of Evolving Synergy • High Angular resolution is increasingly a science-driven requirement for astronomy • Extremely Large Telescopes + next generation AO will redefine the capabilities • Unassailable advantages of space (in UVOIR range) - panoramic imaging (AO always ineffective) - optical and UV: very significant opportunities • JWST does not provide these capabilities • But we can we imagine even larger ground-based or space-based telescopes? Proposed layout of OWL 100m telescope and enclosure Keck Obs. (to scale) Technology Challenge 2020 2000 18m ~ $4B (FY07) 6.5m ~ $4B (FY07) 1980 2.4m ~ $4B (FY07)