SPIDAR: VLF Astronomy on the Moon

1
SPIDAR VLF Astronomy on the Moon

• Jodi Y. Enomoto
• University of Southern California
• ASTE 527 Space Exploration Architectures Concept
  Synthesis Studio
• December 15, 2008

2
Contents

• Context and Rational
• VLF Astronomy
• A New View of the Universe
• Why do we need the Moon?
• South Pole Observatories
• SPIDAR (South Pole Isolated Dipole ARray)
• Optical Interferometer
• Heliograph
• Infrared Interferometer
• Further Studies Future Missions

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Context

• Mission Statement
• Return humans to the Moon for reliably advancing
  and honing Mars Forward technologies and
  experience.
• In the process, establish permanent science
  assets with ASAP returns for all of humanity.
• This presentation mainly focuses on the 2nd
  priority.
• Astronomers are a large and active Origins and
  lunar science from the Moon community.
• How to deploy, calibrate and commission a variety
  of science payloads, using crew, as well as their
  preferred locations spread out globally.

4
Rationale

• Astronomy may not be the reason to go to the
  Moon, but it is definitely something we can do
  that would be beneficial to the scientific
  community and humanity as a whole.

5
VLF Astronomy A New View of the Universe

• What will we find?
• New phenomenon, objects
• Low frequency SETI?

6
VLF AstronomyWhy do we need the Moon?

• Used as a shield
• The Sun Solar Wind, Solar Flares, Coronal Mass
  Ejections
• Large stable platform
• Interferometers with very long baselines
• No propellants or thrusters necessary for
  positioning or formation flying

7
Observatory Locations
Future Missions
Observatory
North Pole Observatory Peary Crater
Mid Latitude Observatory Grimaldi Basin (East
Side, View from Earth)
Far Side Observatory Daedalus or Tsiolkovsky
Crater
South Pole Observatories Mons Malapert,
Shackleton Crater, Schrodinger Basin
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South Pole Observatories
Mons Malapert
Shackleton
Schrodinger
9
Schrodinger BasinSPIDAR Observatory
Transmit to Lunar Base Station
Dipoles
Supporting Cables
Anchors
SPIDAR South Pole Isolated Dipole ARray
Communication Power
5km Diameter
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SPIDAR Observatory A Curved (Hanging Parabola)
Geometry
Allowing some slack the lines would make it more
feasible to achieve an array with a MUCH longer
baseline
SPIDAR South Pole Isolated Dipole ARray
Communication Power
50km Diameter
ABE Artillery Based Explorer
Dec 15, 2008
SPIDAR
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Schrodinger BasinSPIDAR Observatory
Dipoles
Supporting Cables
Anchors
Communication Power
5km Diameter
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Possible Location for SPIDARSchrodinger Lava
Tube
Dark-Halo Crater on the Floor of Schrödinger
Basin Located at 76S, 139E 5 kilometers
across is a volcanic vent that erupted ash during
the period of mare volcanism on the Moon, more
than 3.5 billion years ago.
http//www.lpi.usra.edu/publications/slidesets/cle
m2nd/slide_4.html
5km
High Resolution
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Assumptions

• 14 Lunar surface days.
• Astronauts will assist emplacement of the array
  on the lunar surface.
• Rovers, Tele-Operations, etc.
• Power and communication infrastructure is
  established prior to the observatory
• Lunar libration is accurately accounted for with
  software algorithms.
• Diurnal temperature variation considerations.

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Emplacement of the Array

• Raytheon TOW (Tube-launched, Optically-tracked,
  Wire-guided) Weapon System Technology
• Simple, straight forward approach Shoot a line
  across the crater, secure it, and pull the array
  across.
• Pneumatics and (reusable) spring launchers with
  crossbows.
• Fine adjustments Use a laser (pointing) system
  to indicate desired emplacement points for the
  array.
• After the lines are shot across the distance of
  the crater, astronauts can make fine adjustments
  to the final placement.

Dec 15, 2008
SPIDAR
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Calibration of the Array

• Inertial Measurement Units and Star Trackers
  (with accurate star maps) to accurately estimate
  the position (orientation and curvature) of the
  array
• Curve fitting of each line array
• Interpolate / Extrapolate each element position
• Using laser range finders to get several accurate
  measurements along each line

Dec 15, 2008
SPIDAR
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Calibration

• Inertial Measurement Units and Star Trackers
  (with accurate star maps) to accurately estimate
  the position (orientation and curvature) of the
  array
• Curve fitting of each line array
• Interpolate / Extrapolate each element position
• Using laser range finders to get several accurate
  measurements along each line.

Dec 15, 2008
SPIDAR
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Mons MalapertOptical Interferometer

• Meets the objectives and requirements of the 2005
  ESAS report.
• Location Longitude 0 degrees, latitude 86
  degrees S
• Continuous LOS to Earth for communications link
  capability
• Summit is a large, relatively flat landing area
• 50km in its east-west dimension
• Optical Interferometer placed on Mons Malapert
• 3 or more observatories placed 1km or more apart
• Resolution of milli-arc-seconds to
  micro-arc-seconds

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Mons MalapertOptical Interferometer
http//www.sciencecodex.com/graphics/Altair_Comp.j
pg
19
Space Interferometry Mission Search for
Extrasolar Planets
http//en.wikipedia.org/wiki/Space_Interferometry_
Mission
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Shackleton Crater Heliograph Infrared
Interferometer

• Peak of eternal light ? Heliograph, Solar
  Observation
• Crater of eternal darkness and extremely low
  temperatures ? Infrared Interferometer
• ILOA (International Lunar Observatory
  Association) Planning 3 missions to the Moon
• ILO-X (Precursor)
• ILO-1 (Polar Mission)
• ILOAs Human Service Mission
• Mons Malapert and Shackleton Crater

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Future Studies

• SPIDAR baseline aperture
• Increased for higher resolution capability
• Artillery Based Explorers (ABEs) for array
  emplacement (towed lines)
• Up to 10km (accurate) range
• Calibration of the array
• Accuracy requirements
• Timeline
• Latest ESAS document specifies 14-day missions
• Limits the amount of time on the lunar surface to
  4 days

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Future MissionsA Phased Approach

• Early Missions
• Seismic activity study
• UV, Visible and Infra-red (IR)
• Future Missions with a Permanent Lunar Base
• Observation extra-solar planets, environment,
  surface
• Very long wavelength radio astronomy
• Giant radio telescopes carved out of existing
  craters on the Moon.
• Optical Interferometer
• 3 or more observatories spaced 1km apart.
• ISRU and Giant Liquid Mirror Telescopes (50m)
• Spinning lunar regolith in a circular dish to
  create large parabolic surface.
• Impossible without gravity. However, the Moons
  lower gravity provides the opportunity to achieve
  extremely large scopes.

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References

• http//www.iloa.org/media/Moonbase_Mons_Malapert.p
  df
• http//www.lpi.usra.edu/publications/slidesets/cle
  m2nd/slide_4.html
• http//web.mit.edu/iang/www/pubs/artillery_05.pdf
• Takahashi, Yuki D., New Astronomy From the Moon
  A Lunar Based Very Low Frequency Array,
  Department of Physics and Astronomy, University
  of Glasgow, July 2003
• http//www.sciencecodex.com/graphics/Altair_Comp.j
  pg
• http//en.wikipedia.org/wiki/Space_Interferometry_
  Mission

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• Jodi Y. Enomoto, has 5 years of experience in
  Governmental and Aerospace engineering programs,
  whose interests include attitude determination
  and control systems, digital signal processing,
  and signal processing algorithms for airborne
  radar systems. She has a B.S. degree in EE with
  an emphasis on Control Systems from the
  University of Hawaii, Manoa, and is currently
  pursuing an M.S. degree in EE with an emphasis on
  DSP and Communications at the University of
  Southern California. Her experience related to
  the contents within this document are almost
  entirely limited to the research performed while
  creating this concept in order to fulfill the
  course requirements of ASTE 527 during the Fall
  2008 semester at USC .

Reference
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Back-up slides
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• VLF Astronomy
• http//www.ugcs.caltech.edu/yukimoon/RALF/
• We, humans on Earth, have essentially never
  observed the universe at any wavelengths greater
  than 20m (frequencies below 15MHz) because of
  absorption and scattering by the Earths
  ionosphere.Even at 30MHz (10m), ionospheric phase
  effects limit the interferometry baseline to only
  5km, corresponding to only about 10 arcmin
  resolution.Observing through this new spectral
  range will lead to discoveries of new phenomena
  and new classes of objects.

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Abstract Picture
SPIDAR South Pole Isolated Dipole ARray
Rover Crossbow
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Schrodinger Basin

• Low Frequency SETI and Radio Astronomy
• SPIDAR (South Pole Isolated Dipole ARray)
  Observatory
• Frequencies lt 20 MHz ? Wavelengths gt 15m
• High resolution requires huge antenna aperture
• ILOM (In-situ Lunar Orientation Measurements) and
  LLFAST (Lunar Low Frequency Astronomical
  Observatory) are proposed as plans of
  astronomical observations on the Moon which
  should be realized in a future lunar mission.
  ILOM is a selenodetic mission to study lunar
  rotational dynamics by direct observations of the
  lunar physical libration and the free librations
  from the lunar surface with an accuracy of 1
  millisecond of arc in the post-SELENE project.
  Year-long trajectories of the stars provide
  information on various components of the physical
  librations and we will also try to detect the
  lunar free librations in order to investigate the
  lunar mantle and the liquid core. The PZT on the
  moon is similar to that used for the
  international latitude observations of the Earth
  is applied. The measurement of the rotation of
  the Moon is one of the essential technique to
  obtain the information of the internal structure.
  The highly accurate observation in the very low
  frequency band below about 10 MHz is yet to be
  realized, so that this range is remarkable as one
  of the last frontiers for astronomy. This is
  mainly because that the terrestrial ionosphere
  prevents us from observing the radio waves below
  the ionospheric cutoff frequency on the ground.
  It is, moreover, difficult to observe the faint
  radio waves from planets and celestial objects
  even on the earth's orbit because of the
  interference caused by the solar burst,
  artificial noises and terrestrial aurora
  emissions. The lunar far-side is a suitable site
  for the low frequency astronomical observations,
  because noises from the Earth can always avoided
  and radio waves from the Sun can be shielded
  during the lunar night.

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Scientific Experiments

• Early Missions
• Seismic activity study
• UV, Visible and Infra-red (IR)
• Future Missions
• Observation of extra-solar planets
• Very long wavelength radio astronomy
• Giant radio telescopes carved out of existing
  craters on the Moon.
• Optical Interferometer
• 3 or more observatories spaced 1km apart.
• ISRU and Giant Liquid Mirror Telescopes (50m)
• Spinning lunar regolith in a circular dish to
  create large parabolic surface.
• Impossible without gravity. However, the Moons
  lower gravity provides the opportunity to achieve
  extremely large scopes.

30
Limitations / Showstoppers

• Moon-quakes
• Highly debated. Seismic disturbances were
  measured over the course of 8 years by the Apollo
  missions, showing at most 1 disturbance in a
  given area per year.
• Lunar dust

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Effective Aperture Study

• Effective aperture of a large pseudorandom
  low-frequency dipole arrayEllingson,
  S.W.Antennas and Propagation Society
  International Symposium, 2007 IEEEVolume , Issue
  , 9-15 June 2007 Page(s)1501 - 1504Digital
  Object Identifier   10.1109/APS.2007.4395791Summa
  ryThe long wavelength array (LWA) is a new
  aperture synthesis radio telescope, now in the
  design phase, that will operate at frequencies
  from about 20 MHz to about 80 MHz.This paper
  describes some preliminary estimates of Ae for
  such an array. This is a non-trivial problem
  because the antennas are strongly coupled and
  interact strongly with the ground. To bound the
  scope of this preliminary investigation, the
  antennas are modeled as thin straight half-wave
  (nearly resonant) dipoles, and we restrict our
  attention to the co-polarized fields in the
  principal planes. First, we consider results for
  a single element in isolation. Next, we consider
  the results for the entire array, which are
  compared to the results for the single element
  and also to the physical aperture of the station.

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History VLF Array Design Studies 1990s
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LOFAROperational Since 2006
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• (LOFAR) Low Frequency Array 10-240MHz