Observing the CMB Paul A Fleiner Ph 70 Popular Presentation May 10 2011 Outline Radio Astronomy 21cm Baryon Acoustic Oscillations BAOs Cylinder Telescope Prototype Possible Sites Challenges ID: 254655
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Slide1
The Cylinder Radio Telescope:Observing the CMB
Paul A.
Fleiner
Ph 70 Popular Presentation
May 10, 2011Slide2
Outline
Radio Astronomy
21cm Baryon Acoustic Oscillations (
BAOs
)
Cylinder Telescope
Prototype
Possible Sites
Challenges
Looking AheadSlide3
Radio Astronomy: The Beginning
Early Attempts
Nikola
Tesla, Oliver Lodge
Attempted to observe radio emissions from the sun
Unsuccessful
Technical LimitsSlide4
Radio Astronomy
First RA observations
Karl
Jansky
, 1930s
Bell LabsSlide5
Jansky’s Discovery
Investigating source of interference in short-wave trans-Atlantic transmissions
Initially thought source was solar
Happened every 23 hours, 56 minutes
A
ctually Milky WaySlide6
Modern Radio Telescopes
Very Large Array (VLA)
New Mexico, 1980
$78.5m, ~$10,000/m
2
Square Kilometer Array (SKA)
Australia, 2024
>$2b, $1,000/m
2
(Target)Slide7
How do they work?Slide8
What We “See”
Hydrogen atom moving away from us is
redshifted
:
f
=700MHz
λ
=42cm
Hydrogen atom at rest:
F=1420MHz
λ
=21cm Slide9
Baryon Acoustic Oscillation (BAO)
Method of tracking expansion of universe
About 400,000 years after Big Bang
Universe expanded, temperature cooled
Electrons and protons combine to form H
Photons no longer Thompson scattered
Observing these photons gives us a “ruler” for measuring expansionSlide10
BAO
Can use the ruler to plot the
redshift
Can create a 3D mapping of the universe through
time
Measure the expansion
Will help us quantify “dark energy”Slide11
Cylinder Radio Telescope
Popular from 1960-1980
Abandoned in favor of devices with cryogenically cooled pre-amps
Illinois 400 ft
Telescope, circa
1960 Slide12
CRT Enabling Technology
Low Noise Amplifiers (
LNAs
) are much cheaper
T<<300K
Increased capabilities of Analog to Digital Converters (ADCs)
Better Digital Signal Processing
GPUs
,
FPGAs
More sophisticated
FFTs
(
N log
N)High speed, low power, low costReduces the cost to ~$100/m
2Slide13
CRT Design
Parabolic half-cylinders
Focuses radio waves
radially
inward
Strikes axial array of antennas
Key Requirements
High Resolution
Overall array size, time observed
Large Sky Coverage
Number of channels
Large Redshift
Range
BandwidthSlide14
CMU Prototype
Built by Prof. Peterson’s group in PittsburghSlide15
Goal Design
Array of 10 cylinders
10m wide, 100m long
Coverage
20,000 sq. degrees
Frequency Range
300-1500MHz
Bandwidth
>200MHzSlide16
Challenges
Synchrotron frequency, free-free emission
Total 21cm signal is ~300µK
21cm BAO signal is only ~300nK
Instrument Calibration
Environment Calibration
RF Interference
Far from power lines, most electronicsSlide17
Possible Sites
Several in MoroccoSlide18
Moving Forward
Model removal of foreground noise
Build 2 to 3 cylinders
10m wide, 50m long
Set up larger prototypes in less noisy place
Actually remove noiseSlide19
Acknowledgements
Professor Jeff Peterson, CMU
Kevin
Bandura
, PhD Candidate
Bruce Taylor, Communication and Facilities Consultant