Lunatic fringe: probing the
dark ages from the dark side
of the Moon
C. Carilli (NRAO)
Enchanted Skies
Socorro, NM
Sept. 2008
Ionized f(HI) ~ 0
Neutral f(HI) ~ 1
Reionized f(HI) ~ 1e-5
History of
Baryons in the
Universe
Chris Carilli (NRAO)
Berlin June 29, 2005
WMAP – structure from the
big bang (/~ 1e-5)
Hubble Space Telescope
Realm of the Galaxies
/ ~ 1e5
Dark Ages
Twilight Zone
Epoch of
Reionization
• Last phase of cosmic
evolution to be tested
• Bench-mark in cosmic
structure formation
indicating the first
luminous structures
Dark Ages
Twilight Zone
Epoch of
Reionization
• Epoch?
• Process?
• Sources?
Dark Ages
SDSS J1148+5251
tuniv ~ 0.87 Gyr
Twilight Zone
Pushing into reionization:
most distant galaxies and
quasars
Gunn-Peterson Effect
z
Barkana and Loeb 2001
0.87
Gyr
First constraints on
cosmic reionization
• Gunn-Peterson Effect
toward z~6 QSO =
absorption by the neutral
intergalactic medium
(IGM) at tuniv < 1Gyr
• From tuniv ~ 0.87 to 1.0
Gyr, neutral fraction
changes by order of
magnitude
1.0
Reionization: the movie
Gnedin 03
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
8Mpc
comoving
Most direct probe of the neutral IGM during, and prior to,
cosmic reionization, is the 21cm line of neutral hydrogen
Radio => Hydrogen Gas
HI spin flip =>
21cm radiation
(1420 MHz)
400Myr, 109MHz
600Myr, 142 MHz
800Myr, 178MHz
 3D ‘tomography’ of the evolution of the large scale structure of
the IGM: “richest of all cosmological data sets” (Loeb)
 Low frequencies: Universal expansion (‘redshift’) implies HI
21cm line will be observed at < 200 MHz
Weak signal requires very large area telescopes ‘Square
kilometer array’
Multiple experiments under-way
MWA (Oz; MIT/CfA/ANU)
21CMA (China)
LOFAR (NL)
21CMA (China)
Takla Makan Desert
10,000 TV antennas
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Challenge I: Low frequency foreground – hot, confused sky
Eberg 408 MHz Image (Haslam + 1982)
Cosmological signal ~ 0.00001 x Sky
Challenge II: Ionospheric ‘seeing’
Fluctuations in ionospheric
electron content causes
interferometric phase errors
at low radio frequencies ~
‘radio seeing’
Challenge II: Ionospheric ‘seeing’
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
15’
Virgo A 6 hrs VLA 74 MHz Lane + 02
Challenge III: Interference
100 MHz
z=13
200 MHz
z=6
Solutions -- RFI Mitigation (Ellingson06)
 Digital filtering: multi-bit sampling for high
dynamic range (>50dB)
 Beam nulling/Real-time ‘reference beam’
 LOCATION!
VLA-VHF: 180 – 200 MHz Prime focus CSS search Greenhill,
Blundell (SAO); Carilli, Perley (NRAO)
Leverage: existing telescopes,
IF, correlator, operations
 $110K D+D/construction (CfA)
 First light: Feb 16, 05
 Four element interferometry: May 05
 First limits: Winter 06/07
Project abandoned: Digital TV
KNMD Ch 9
150W at 100km
RFI mitigation: location, location location…
100 people km^-2
1 km^-2
0.01 km^-2
(Briggs 2005)
Murchison widefield array
(MIT - Melbourne)
Radio astronomers
going to the ends of
the Earth
Precision Array to Probe the
Epoch of Reionization
(Berkeley -- NRAO)
Ultimate location: the dark
side of the Moon
Long History of Lunar Low Freq Telescope
Lunar
window
ion. cutoff
~ 30m
ISM cutoff ~ 3km
Gorgolewski 1965: Ionospheric opacity
• Ionosphere opaque below 10 MHz
• Interstellar medium opaque below 0.1 MHz
• tuniv < 10Myr => not (very) relevant for HI 21cm studies, ‘beyond dark
ages’
Return to moon is Presidential
national security directive
(an order, not a request).
Summary of STScI Workshop,
Mario Livio, Nov. 2006
“The workshop has identified a few
important astrophysical
observations that can potentially
be carried out from the lunar
surface. The two most promising
in this respect are:
(i)
Low-frequency radio observations
from the lunar far side to probe
structures in the high redshift (10
< z< 100) universe and the epoch
of reionization
(ii) Lunar ranging experiments…”
Heavy lifting: capitalize on
future launch vehicles
Ares V
• 10m diameter faring
• Lifting power = 65 tons to Moon
Ares I
Ares V
Lunar advantage I: ultra-thin ionosphere
Soviet LUNA orbiters in 1970’s detected plasma layer > 10 km above surface
 Apollo surface+subsatellite: detected photoionized layer extending to 100km
 p = 0.2 to 1 MHz
 large day/night variation => two weeks of ionosphere-free night-time

Clementine (NRL)
star tracker
Advantage II: Interference
Lunar shielding of Earth’s auroral
emission at low freq (Radio Astronomy
Explorer 1975)
12MHz
Alexander + 1975
The Moon is radio protected
ARTICLE 22
(ITU Radio Regulations)
Space services
Section V – Radio astronomy in the shielded zone of the Moon
22.22 § 8 1) In the shielded zone of the Moon31 emissions causing
harmful interference to radio astronomy observations32 and to other
users of passive services shall be prohibited in the entire frequency
spectrum except in the following bands:
22.23 a) the frequency bands allocated to the space research service
using active sensors;
22.24 b) the frequency bands allocated to the space operation service,
the Earth exploration-satellite service using active sensors, and the
radiolocation service using stations on spaceborne platforms, which are
required for the support of space research, as well as for
radiocommunications and space research transmissions within the
lunar shielded zone.
22.25 2) In frequency bands in which emissions are not prohibited by
Nos. 22.22 to 22.24, radio astronomy observations and passive space
research in the shielded zone of the Moon may be protected from
harmful interference by agreement between administrations concerned.
Other advantages
• Easier deployment: robotic or human
• Easier maintenance (no moving parts)
• Less demanding hardware tolerances
• Very large collecting area, undisturbed for long periods (no
weather, no animals, not many people)
Deployment
• Javelin
• ROLS: polyimide circuit-imprinted film
• Dipoles: robotic with rover
• Dipoles: manually
Array of lunar
sensors (Falcke)
• ‘Lunar internet’
• Cherenkov radiation
from neutrinos passing
through the lunar regolith
• Geophones: lunar
seismology
Lunar challenges
• Array data rates (Tb/s) >> telemetry limits,
requiring in situ processing, ie. low power
super computing (LOFAR/Blue Gene =
0.15MW)
• RFI shielding: How far around limb is
required?
• Thermal cycling (mean): 120 K to 380 K
• Radiation environment
• Regolith: dielectric/magnetic properties
Lunar shielding at
60kHz
Takahashi + Woan
Apollo 15
Energy solutions: polar craters of eternal
darkness, peaks of eternal light = eternal
power
Tsiolkovsky crater
(100 km diameter)
20°S 129°E
But how sharp is the
knife’s edge?
Apollo 15
DALI - LAMA: A path to enlightenment
NASA funded joint design study
• Dark Ages Lunar Interferometer (Lazio)
• Lunar Array for Measuring 21cm Anisotropies (Hewitt)
Science (Loeb, Furlanetto)
Science requirements (Carilli, Taylor)
Antennas (Bradley, MacDowall)
Receivers (Backer, Ellingson)
Correlator (Ford, Kasper)
Data communication (Ford, Neff)
Site selection (Hoffman, Burns)
Deployment (de Weck, DeMaio)
Engineering: power/mech/therm
Goal: Decade Survey 2010
white paper with mission
concept, (rough) costing,
and technological roadmap
<2010: mission concept study
Very long
range
planning!
Interim programs
2010 -- 2020: technology development
•Orbiter: RFI, ion
• First dipoles:
environ., phase
stability
2020 -- 2025: Design/Fabrication/Test
2026+: operations
• Global signal
Budget WAG (Hewitt/LARC)
+ ARES V Launch fee ~ $700M
Total ~ $2G
European Aeronautic Defense and Space Corporation/ASTRON (Falcke)
• Payload = 1000 kg (Ariane V)
• 100 antennas at 1-10 MHz ~ 1/10 SKA
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
Say, its only a PAPER moon
Sailing over a cardboard sea
But it wouldn't be make-believe
If you believed in me
END
CMB large scale
polarization -- Thomson
scattering during
reionization
 Scattering => polarized
 Large scale: horizon scale at
reionization ~ 10’s deg
 Signal is weak: only 1% of T
=> finite ionization persisting
to tuniv ~ 0.4Gyr
Page et al. 2006
Combined
CMB + GP
constraints on
reionization
Not ‘event’ but complex process, large variance in space and time,
starting ~ 400 Myr after Big Bang, ending ~ 800 Myr after BB.
Combined
CMB + GP
constraints on
reionization
Current probes are all fundamentally limited in diagnostic power: Need
more direct probe of process of reionization
Doppler effect – follow those lines!
The amazing and EXPANDING universe
1 dR 2 GMm
2 / 3 dR
m( ) 
 R  t ;
 t 1/ 3
2
dt
R
dt
Contents of the Universe:
•70% Dark Energy
•27% Dark Matter
•3% Baryons
C. Carilli, A. Datta (NRAO), J. Aguirre (Penn)
Focus: Reionization (power spec,CSS,abs)
PAPER: Staged Engineering
• Broad band sleeve dipole + flaps
• 8 dipole test array in GB (06/07) => 32
station array in WA (2008) to 256 (2009)
• FPGA-based ‘pocket correlator’ from
Berkeley wireless lab: easily scale-able
• S/W Imaging, calibration, PS analysis:
AIPY + Miriad/AIPS => Python + CASA,
including ionospheric ‘peeling’ calibration
100MHz
BEE2: 5 FPGAs, 500 Gops/s
200MHz
PAPER/WA -- 4 Ant, July 2007
RMS ~ 1Jy; DNR ~ 1e4
1e4Jy
Parsons et al. 2008
CygA 1e4Jy