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

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Science Enabled by the Exploration Architecture (and return to the Moon) John Mather NASA Goddard Space Flight Center STScI, Nov. 29, 3006 – PowerPoint PPT presentation

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Title: 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

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?

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

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)

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)

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

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?

8
Stiffening a Big Telescope for 1/6 g
  • No way to make a passively stable system highly
    precise, gt 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.

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

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?

11
Radio Telescopes
  • Long wavelength (gt 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

12
Servicing Possibilities
  • Lunar surface advantages
  • Cant get lost on lunar surface, but must travel
    by car or on foot
  • Tools cant 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

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

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 - dont 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

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

16
Planet Finders (2)
  • SIM
  • Requires complete thermal stability and wide sky
    view
  • Dark crater potential site, but loses gt 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

17
Site Survey the Moon and Free Space (e.g. L2)
Item Lunar Surface Free Space (e.g. Sun -Earth L2)
Delivered payload mass per launch (implies launch cost difference) 1/3 (depends on Isp of propulsion, many details) 1
Gravity g/6, causes sag of optical system vs. pointing, needs stiff structures, added mass. Enables spin-formed parabolic mirror with vertical axis (R. Angel, P. Worden) 0
Servicing, repair, upgrade Six Apollo missions 1969 -- 1972 few days trip each way, limited radiation exposure to astronauts. Shuttle missions for HST, ISS, CGRO robotic arms numerous robotic designs. Sun-Earth L2 much farther from Earth than Moon. Possible service center at Earth-Moon L1.
Dust Sticky, small, charged, naturally levitated above surface activated by astronauts, rovers, and retrojets seen by astronauts evidence of accumulation on retroreflectors 0
Solar power duty cycle 14 days/29, except polar peaks (1) or dark craters (0), may require storage for lunar night 1
Communications duty cycle 1 on front, needs relay on backside or deep crater 1
Temperature variation of environment Variable solar direction (except in dark craters) requires complex sunshield designs Constant solar direction permits simple sunshield designs.
Observing duty cycle Depending on stray light shields, power, thermal protection and stability, and comm 1
Field of Regard Depends on lunar latitude and horizon shape inside thermal shields Whole sky
Interferometer baseline maintenance Passive, cant get lost. Fixed positions, or movement across challenging terrain Active servos, full (u,v) coverage. Requires station keeping and propulsion.
Path length compensation Long range (comparable to spacing of collectors), to obtain field of view and (u,v) coverage Short range (few cm), as part of formation flying servo control loop
Maximum baseline Size of flat region on Moon Optics limited, huge
Radio quiet Far from Earth back side is protected for now Can be much farther from Earth
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 AOs for science
  • Astronomers are ingenious theyll find a way to
    use the infrastructure or the lunar surface!

19
In the meantime
  • Assess possible augmentations to Exploration
    Architecture with joint benefits to science and
    manned program
  • Study potential radio astronomy at ? gt 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

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 were 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 AOs
  • 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
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