Transcript Melissa Doyle - University of Southern California

SPIDAR:
VLF Astronomy on the Moon
Jodi Y. Enomoto
University of Southern California
ASTE 527: Space Exploration Architectures
Concept Synthesis Studio
December 15, 2008
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
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
Context
•
Mission Statement:
1. Return humans to the Moon for reliably
advancing and honing Mars Forward
technologies and experience.
2. 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.
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
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.”
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
VLF Astronomy:
A New View of the Universe
• What will we find?
• New phenomenon, objects…
• Low frequency SETI?
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
VLF Astronomy:
Why 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
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
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
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
South Pole Observatories
Mons Malapert
Shackleton
Schrodinger
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
Schrodinger Basin:
SPIDAR Observatory
Transmit to Lunar
Base Station
Dipoles
Supporting
Cables
“Anchors”
SPIDAR
South
Pole
Isolated
Dipole
ARray
Communication
& Power
Rover +
Crossbow
Length = 50 x
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
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
Rover +
ABE’s
Length = 500 x
“ABE” = Artillery Based Explorer
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
Schrodinger Basin:
SPIDAR Observatory
SPIDAR System Parameters
Site
Dipoles
Schrodinger
Supporting Basin
Cables
1MHz
Frequency
“Anchors”
λ = 300m
Wavelength
λ/2 = 150m
Dipole Spacing
Communication
Number of Elements
& Power
500
Aperture
5km
Bandwidth
~100kHz
Resolution
TBD
Lifetime
20+ years
Weight (Earth value)
Rover +
Crossbow
Array
< 1000kg
Anchors
< 50kg
Length = 50 x
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
Possible Location for SPIDAR:
Schrodinger Lava Tube
Dark-Halo Crater on the Floor of Schrödinger Basin
Located at 76°S, 139°E
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/clem2nd/slide_4.html
5km
High Resolution
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
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.
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
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.
•
•
•
•
Dec 15, 2008
After the lines are shot across the distance of the crater,
astronauts can make fine adjustments to the final
placement.
SPIDAR
Jodi Y. Enomoto
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
Jodi Y. Enomoto
Calibration
•
Inertial Measurement Units and Star
Trackers (with accurate star maps) to
accurately estimate the position (orientation
and curvature) of the array
•
•
•
Dec 15, 2008
Curve fitting of each line array
Interpolate / Extrapolate each element position
Using laser range finders to get several
accurate measurements along each line.
SPIDAR
Jodi Y. Enomoto
Mons Malapert:
Optical 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
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
Mons Malapert:
Optical Interferometer
http://www.sciencecodex.com/graphics/Altair_Comp.jpg
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
Space Interferometry Mission:
Search for Extrasolar Planets
http://en.wikipedia.org/wiki/Space_Interferometry_Mission
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
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)
ILOA’s Human Service Mission
Mons Malapert and Shackleton Crater
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
Future Studies…
• SPIDAR baseline aperture
– Increased for higher resolution capability
• Artillery Based Explorers (ABE’s) 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
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
Future Missions…
A 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 Moon’s lower gravity
provides the opportunity to achieve extremely large scopes.
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
References
1.
2.
3.
4.
http://www.iloa.org/media/Moonbase_Mons_Malapert.pdf
http://www.lpi.usra.edu/publications/slidesets/clem2nd/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
5. http://www.sciencecodex.com/graphics/Altair_Comp.jpg
6. http://en.wikipedia.org/wiki/Space_Interferometry_Mission
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
Reference:
•
Dec 15, 2008
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
.
SPIDAR
Jodi Y. Enomoto
BACK-UP SLIDES
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
• 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 Earth’s
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.
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
Abstract Picture
SPIDAR
South
Pole
Isolated
Dipole
ARray
Rover +
Crossbow
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
Schrodinger Basin
• Low Frequency SETI and Radio Astronomy
• SPIDAR (South Pole Isolated Dipole ARray)
Observatory
– Frequencies < 20 MHz  Wavelengths > 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.
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
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 Moon’s lower gravity
provides the opportunity to achieve extremely large scopes.
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
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
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
Effective Aperture Study
• Effective aperture of a large pseudorandom low-frequency
dipole array
Ellingson, S.W.
Antennas and Propagation Society International Symposium, 2007
IEEE
Volume , Issue , 9-15 June 2007 Page(s):1501 - 1504
Digital Object Identifier 10.1109/APS.2007.4395791
Summary:The 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.
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
History: VLF Array Design Studies
1990’s
Dec 15, 2008
SPIDAR
Jodi Y. Enomoto
LOFAR;
Operational Since 2006
(LOFAR) Low Frequency Array: 10-240MHz
Dec 15, 2008
SPIDAR
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Jodi Y. Enomoto