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Transcript of Open Source Radio Telescope · • Dr. Richard Prestage, Green Bank Observatory • Sue Ann...
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Open Source Radio Telescope
Introduction
After a brief presentation of Richard Prestage’s talk on
Digital Signal Processing in Radio Astronomy – a Research Experience
for Teachers
John Makous will give a longer presentation on
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Open Source Radio Telescope• http://opensourceradiotelescopes.org/
• a resource for radio astronomy telescope construction at any level, from simple feed horns to phased-array feeds and interferometers.
• Discussion Forums
• Telescope Designs
• LightWork Memo Series
• Additional Resources:▪ Larger Scale Home Built Radio Telescope, Radio Astronomy Supplies
▪ Canadian Centre for Experimental Radio Astronomy (CCERA)
▪ Digital Signal Processing in Radio Astronomy (DSPIRA)
▪ Society of Amateur Radio Astronomers (SARA)
▪ Such A Lovely Small Antenna (SALSA)
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Digital Signal Processing in Radio Astronomy – a Research Experience
for Teachers
John L. Makous
Providence Day School
Charlotte, NC
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Outline• Introduction
• Design and construction
• Operation and capabilities
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Introduction – Horn Telescopes
• This talk is the result of 2 summers attending the RET DSPIRA program at WVU and GBO.
• The horn telescopes described here are designed to detect the 21 cm radio waves transmitted by neutral atomic hydrogen (HI) emitted by interstellar hydrogen in the galaxy.
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Horn Telescope Design
Horn• aluminized
insulation board
• 60 cm x 75 cm horn opening
Waveguide & Antenna
• 4 ½ ” x 6 ½ ” metal can
• ¼ wave antenna: 5.25 cm
Stand - constructed from 2” x 2” and 2” x 4” wood
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Low noise amplifier:• optimized for 21 cm radio waves at 1420.4 MHz• gain = 50 db• Stabilized for operation in urban environments
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Horn Telescope Operation
Software Defined Radio (SDR)
• Airspy radio
– 24 MHz – 1800 MHz range
– 10 MHz bandwidth
• Gnuradio program:
– used to perform the signal processing
– free & open source
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Horn Telescope Calibration
Calibrated Scans on the Run
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Horn Calibration● Signals detected include inputs from extraneous sources
Pmeasured = G x (Tobject + Tsystem)
Pmeasured = detected signalG = gainTobject = signal from object of interest
(galaxy, pulsar, etc.)Tsystem = signal from extraneous sources
● Calibration involves measuring spectra of 2 known temperatures
● “Thot” = temperature of ground = 300 K (assumed)
● “Tcold” = temperature of empty sky = 10 K (assumed)
These are all functions of frequency
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Horn Calibration● By collecting spectra of the ground and empty sky, the gain and system
temperature can be determined:
G =
Tsystem =
Phot - Pcold
Thot - Tcold
Thot - Tcold(Phot /Pcold)
(Phot /Pcold) - 1
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Calibration on the Fly
● We built a gnuradio block to accommodate
calibration runs that can be incorporated into the live
display during a run
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Features of the Calibration Block & Display
Adjust signal scale
Collection/Display Option
Print display to file
Write to .h5 file
System Temperature
GainSource
Histogram
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1. Point and collect cold calibration
2. Point and collect
hot calibration
3. Choose
Spectrum with
Calibration
Calibration Procedure
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Tsys ≅ 75 K
Calibrated Spectrum Displayed
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Future Modifications
Order pizza
1. Integration input2. Save calibrations for future runs
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Horn Telescope Performance• Can detect neutral hydrogen (HI) from the
Milky Way Galaxy.
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Students can measure the Doppler shift of the hydrogen signal from the expected 1420.4 MHz
➔ the MW galaxy is rotating!
T sky
(K)
Gal. Long. = 53o
unshifted
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Possible Projects
• Interferometry
• Pulsar detection
• Fast Radio Burst detection
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Implementation in the classroomUtilizing a horn telescope covers many STEM standards:
• Math – in all phases of use
• Engineering & Technology – build/design horns, test/modify cycle
• Computer programming – gnuradio, python
• Astronomy– radio waves, EM spectrum, signals, energy
– telescopes: purpose & design, astronomical measurements
– structure and motion of galaxies
• Physics– Kepler’s laws, motions of galaxies, dark matter
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Rich in Science Standards
Horn Telescope Activity
Science & Engineering Practices
Disciplinary Core Ideas
Crosscutting Concepts
Measuring H1 spectrum;
determining rotation curve
Developing and using models
ESS1.B – Kepler’slaws, orbits, etc.
Scale, Proportion, and Quantity
Using mathematical and computationalthinking
PS4.B – EM Radiation
Interdependence of Science, Engineering, and Technology
Constructing Explanations and Designing Solutions
Scientific Knowledge Assumes an Order and Consistency in Natural Systems
Science Models, Laws, Mechanisms, and Theories Explain Natural Phenomena
NGSS HS.Space Systems
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SUMMARYHorn telescopes offer:
• Rich STEM experience for students
• Hands-on science – learn by doing
• Ability for students to develop and/or test models of nature
• Ability for students to experience a part of the world of digital signals
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AcknowledgementsWe would like to thank the following for their expertise, patience, and support:
• Dr. Kevin Bandura, West Virginia University• Dr. Natalia Schmid, West Virginia University• Dr. Loren Anderson, West Virginia University• Dr. Richard Prestage, Green Bank Observatory• Sue Ann Heatherly, Green Bank Observatory• Pranav Sanghavi, West Virginia University
We would like to thank the following for their generous support and contributions to the Research Experience for Teachers in Digital Signal Processing in Radio Astronomy (RET DSPIRA) program:
• National Science Foundation• West Virginia University• Green Bank Observatory
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RET DSPIRA PROGRAM
• Kevin Bandura
• Sue Ann Heatherly (at Green Bank Observatory)