Science Enabled by the Exploration Architecture (and return to the Moon)

1. Science Enabled by the Exploration Architecture (and return to the Moon) John Mather NASA Goddard Space Flight Center STScI, Nov. 29, 3006 Mather STScI Lunar Astrophysics

2. Key Strategic Questions • What scientific questions are ripe for the next few decades? • What scientific questions are worth the money to do in space? • Site surveys: advantages of the lunar surface and free space? • Robots or astronauts: which goals need which systems? • For given requirement, what are cost differences between sites? • How much does it all cost? Mather STScI Lunar Astrophysics

3. Possible Hardware for Human Space Exploration • Orion (Crew Exploration Vehicle, CEV, under design/ construction) • Ares 1 (Crew Launch Vehicle, CLV, under design/ construction) • Ares 5 (Cargo Launch Vehicle, CaLV much larger) • Lunar Surface Access Module (LSAM) • Earth Departure Stage (EDS, cryo upper stage of Ares 5) • Advanced space suits Mather STScI Lunar Astrophysics

4. Hardware (2) • Advanced servicing capabilities • Remote robotic • Local astronaut-controlled robots/manipulators • EVAs • Advanced habitat equipment • Astronaut safety: centrifuges, shields, possibly from local materials • Life support: food production, recycling • Solar and nuclear power and communication • Service stations at Earth-Moon L1, Sun-Earth L2 (later) Mather STScI Lunar Astrophysics

5. Hardware Enabling New Astrophysics • CEV and CLV, under design for construction • New sites on Moon • Servicing at new locations not on Moon • Advanced servicing capabilities - TBD, very important to astrophysics • Very remote robotic (e.g. operated from ground) • Local astronaut-controlled robots/manipulators • EVA - depends on airlocks and many details • Ares 5 (Cargo Launch Vehicle, CaLV) • Larger payloads, farther away or faster • Advanced habitat development • Solar and nuclear power and communication • Service stations at Earth-Moon L1, Sun-Earth L2 (later) Mather STScI Lunar Astrophysics

6. Important Astro- & Solar System Physics from the Moon • Lunar geology: sample recognition, analysis, excavation, return to Earth • Lunar structure: mapping, gravity, surface and interior chemistry and physics • Lunar origin • Solar system archeology, by interpretation of samples • Laser ranging from Earth, to test Einstein Mather STScI Lunar Astrophysics

7. Payload Mass • For JWST, launch vehicle cost ~ 3-4% of life cycle cost, but launcher imposes strict mass limit • If same mass were landed on the Moon, would need ~ 3x launcher capability, perhaps rocket cost would scale in proportion? • Cost estimation algorithms for observatories say cost and mass are ~ proportional, so 6000 kg is about the maximum for a JWST-class telescope anywhere • Does this apply to observatory alone, or including landing equipment? Mather STScI Lunar Astrophysics

8. Stiffening a Big Telescope for 1/6 g • No way to make a passively stable system highly precise, ==> need active control loops re-adjusted for each elevation angle • Like adaptive optics on ground, but much slower - OK but complicated • Strength not an issue, since launch loads are much larger • For R. Angel concept of spinning liquid mirror, gravity is required, but there is no possibility of changing its axis from vertical. Mather STScI Lunar Astrophysics

9. Dust • Lunar dust is hazardous - sharp, small, sticky, covers astronauts, requires cleaning to get vacuum seals on suits • Lunar dust levitates due to electrostatic forces, seen by astronauts as a haze • Laser retroreflectors may be contaminated by dust - more info needed • A serious engineering challenge to manage dust around telescopes Mather STScI Lunar Astrophysics

10. Optical Interferometers • On Earth or Moon, complicated optical systems with path length equalization systems and huge rooms filled with trolleys and mirrors • Servicing might be necessary - ground based equipment is hard to adjust • Free-space version optically much simpler • Path equalization by formation flying • May still need servicing? Mather STScI Lunar Astrophysics

11. Radio Telescopes • Long wavelength (> 30 m) needs space • Very little is known in this band, wide open for exploration and surprise, but so far not recognized by NAS as top scientific priority • New generation ground-based observatories will allow extrapolation from higher frequencies • Need large array of dipoles to image large areas of sky • High angular resolution needs huge array •  = /d • 1 arcsec at 30 m means 6000 km span • Reconfigure array to match required  • TBD how quiet the environment must be Mather STScI Lunar Astrophysics

12. Servicing Possibilities • Lunar surface advantages • Can’t get lost on lunar surface, but must travel by car or on foot • Tools can’t escape • Astronauts could have permanent safe home (far future), always available to service complex observatories • Free space advantages • Can be anywhere the telescope is, or can go • LEO to EM L1 to SE L2 to … • Equipment is weightless - no lifting fixtures • No dust to contaminate telescope & tools • Extensive experience with HST, Space Station • Astronauts can come home from EM L1 in a flash if bad solar weather Mather STScI Lunar Astrophysics

13. Possible Servicing Uses • CEV • How far can it go to do servicing? • Quick astronaut trip to SE L2? (too risky if EM L1 would be enough, but maybe later…) • Robotic servicing, e.g. using astronaut tools and manipulator arms, to reduce risk or enable upgrades • Beyond Einstein probes - servicing probably not needed, but …? • Interplanetary missions, robot explorers? • Future Great Observatories • Chandra, LISA, SIM, TPF-C, TPF-I, TPF-Occulter, SAFIR… Mather STScI Lunar Astrophysics

14. Future Large Observatories from Decadal Survey • Chandra X-ray observatory • Lunar surface bad for very precise optics, free space good, servicing possibly valuable • LISA gravity wave observatory • Lunar site impossible, remote servicing possible by replacing a member of the triangle with a new one (no robot or astronaut visit needed) • SAFIR far IR telescope • Lunar surface much too hot except possibly in dark crater - don’t know this yet, need ~ 4 K cooling for ~ 10 m telescope • SPECS and SPIRIT, far IR interferometers • ~ 4 K telescopes at all possible spacings in (u,v) plane • Lunar surface not possible - too hot, telescopes not mobile Mather STScI Lunar Astrophysics

15. Planet Finders • Kepler: transit search, 2008 launch • Continuous monitoring of Cygnus region, declination ~ 40o +/- 23o • Dark crater at North lunar pole? target elevation ~ 40o +/- 23.5o • Microlensing Planet Finder (Discovery proposal) • Requires continuous monitoring of Galactic Center • GC is in Ecliptic Plane, ~ on horizon from Lunar poles • Nearest Star Planet Transit Survey (extends ground-based surveys with better photometry) • Like Kepler, but all-sky survey, to find nearest and brightest, best candidates for follow-up by JWST, etc. • Lunar pole locations possible; need 2 for all-sky Mather STScI Lunar Astrophysics

16. Planet Finders (2) • SIM • Requires complete thermal stability and wide sky view • Dark crater potential site, but loses > half of targets • TPF-Coronagraph • Lunar surface probably impossible - optical system must be /3000 and perfectly stable, and extremely clean (no dust at all!) • TPF-Interferometer • Lunar surface probably impossible - but worth some study • Filling (u,v) plane much easier in space than on surface of Moon • New Worlds Observer - remote occulter • Lunar surface impossible - formation flight configuration with ~25,000 km spacing Mather STScI Lunar Astrophysics

17. Site Survey: the Moon and Free Space (e.g. L2) Mather STScI Lunar Astrophysics

18. What would I do? • Coordinate with manned program to assess capabilities needed by both manned program and science • Understand approach of manned program to manage dust, and what equipment and infrastructure they will develop and when • Study how much dust contaminates lunar optics, and how to mitigate it • Study how to design astronomical equipment ON Moon • AFTER manned program is defined, lunar sites and habitats are selected, and infrastructure is known • Lunar Astronomy is NOT a driver for the manned program - plenty of other ways, currently easier, to do science • Present to NAS review for comparison to other sites • Offer new observing sites and infrastructure in competitive AO’s for science • Astronomers are ingenious: they’ll find a way to use the infrastructure or the lunar surface! Mather STScI Lunar Astrophysics

19. In the meantime • Assess possible augmentations to Exploration Architecture with joint benefits to science and manned program • Study potential radio astronomy at  > 30 m: does it justify space equipment? • Study (with AAAC) what equipment matches the scientific goals for exoplanets - if very complex or risky, servicing may be appropriate • Study (with NAS) what has priority in next decade for space and ground-based astronomy • If top priorities could benefit from the VSE infrastructure, do needed studies Mather STScI Lunar Astrophysics

20. Summary and Conclusions • Exploration Architecture & infrastructure (heavy lift vehicles, CEV, robotic servicing) could enable much more powerful large observatories, in free space, with much longer useful lifetimes, than are possible today • Since we’re going to the Moon, then study the Moon itself • Lunar surface not best use of money for most telescopic astronomy, but when manned program is defined, then offer lunar sites and infrastructure in AO’s • Astronomy is NOT a driver for manned program requirements - too many other ways to do most science, and conflicting program requirements drive up costs • For specific science, e.g. gravity studies by laser retroreflector, lunar placement is very important • Need to know whether (expensive, fragile) human presence is required on-site for astrophysics missions Mather STScI Lunar Astrophysics