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Linux, SETI, and Radio Astronomy Marcus Leech Radio Science Laboratories http://www.radio-science-labs.com. Image appears courtesy NRAO/AUI. What is Radio Astronomy?. Astronomy at wavelengths from a few mm to tens of meters - PowerPoint PPT Presentation
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Linux, SETI, and Radio AstronomyMarcus Leech
Radio Science Laboratorieshttp://www.radio-science-labs.com
Image appears courtesy NRAO/AUI
What is Radio Astronomy?
Astronomy at wavelengths from a few mm to tens of meters
Visible light has wavelengths in the region of 500nm, that is, 5.0x10-7 meters
From a physics standpoint, there's no difference between visible light, and microwave/radio-wave “light”.
Living things have receptors for only a tiny part of the EM spectrum
Optical vs Radio Astronomy Ability to resolve fine detail highly dependent on
wavelength A 10cm optical telescope can resolve details that
would require a radio telescope over 42km in diameter at 21cm wavelength!
Sensitivity, however, is proportional to collecting area of the reflector, regardless of wavelength Both use parabolic reflectors Both must have a surface that is within 1/10th of
wavelength of perfect for maximum efficiency.
History of Radio Astronomy
Like much in science, it was discovered accidentally
Karl Jansky, 1933, working on sources of static on international radio-telephone circuits at wavelengths of 10-20M.
Discovered that static rose and fell with a period of 23 hours, 56 minutes. Must be of celestial origin
The Genesis of Radio Astronomy Science Jansky was re-assigned to other projects after his
work on radio-telephone “hiss”. Several years went by with nobody understanding
the significance of his discovery Grote Reber picked up on Janskys work in 1937,
building a 30ft dish in his back yard. Eventually mapped entire Milky Way emission at
160Mhz (1.8M wavelength) Published in Astrophysical Journal in 1944
Radio Astronomy now taken seriously
Grote Rebers Dish Now preserved as historical artefact at NRAO, Green Bank, West Virginia
Radio Astronomy Today Radio Astronomy at the cutting-edge of
astrophysical research Roughly 70% of what we know today about the universe
and its dynamics is due to radio astronomy observations, rather than optical observations
Big projects all over the world VLA, New Mexico Arecibo, Puerto Rico GBT, Green Bank, West Virginia Westerbork, Jodrell Bank, ALMA, Hat Creek, SKA, etc
Scientists named the basic flux unit after Karl Jansky 1 Jansky == 10-26 watts/hz/meter2
SETI
Drake equation:
N = R* x Fp * Ne x Fl x Fi x Fc x L N number of potential ET civilizations R* rate of star formation Fraction of stellar systems with planets Ne fraction planets that can support life Fl fraction that actually produce life Fi Fraction that develop intelligent life Fc fraction that develop detectable technologies (radio, etc) L length of time such civilizations emit (lifetime)
SETI contd Many observing programs over the years
Harvard: META and BETA
SERENDIP I/II
NASA: HRMS
Cancelled after only 1 year by senator Richard Bryan
“This hopefully will be the end of Martian hunting season at
taxpayers expense”
Was a comparatively-small NASA program
Personnel went on to form the SETI Institute
SETI@Home -- using data gathered mostly at Arecibo
SETI Science/Engineering Look for narrowband (~1Hz wide) signals coming from “out there”.
Eliminate terrestrial sources (interference, etc)
See if signals have appropriate doppler drift (chirp)
Do they fit the profile of the antenna pattern?
Need for wideband, high-resolution spectrometers
Usually done in ASIC implementing high-speed FFT
SDR can play a role
Gnu Radio, SDR, Linux SDR Software Defined Radio
Software to replace traditional hardware functions
FAST A/D and D/A hardware
REALLY FAST compute platforms
GNU Radio
Open Source toolkit for SDR
Cost-effective (like, free) solution for experimental
RF/Microwave work.
SDR Hardware Provides basic RF interface
High-speed A/D and D/A
down/upconversion to/from baseband signals
Some digital filtering
Many hardware platforms
USRP Universal Software Radio Peripheral
http://www.ettus.com
Beefy gamers-class PC platform: Q6600 3.5GHz, 8GB memory
SDR RA/SETI Software Developed gr-radio-astronomy subtree of Gnu Radio
Provides basic RA and SETI tools
Open Source
New IRA software:
Fully integrated RA/SETI receive chain
SETI up to 16Million 1Hz channels
Pulsar, Total Power, Spectral, Transients
http://www.science-radio-labs.com
GNU Radio Development Tools Python and C++ can be used to assemble so-called
flow graphs.
Signal processing chain
GRC
Graphical tool to generate flow-graphs, using
MATLAB/LabView like interface.
Example GRC flow graph
Flowgraphs and GUIs
Lots of different applications built with GNU
Radio and various GUI toolkits.
All-mode HF transceiver
RADAR
GPS
Radio Astronomy
Gnu Radio Application example
IRA Software RA/SETI all-mode receiver
Based on XFORMs toolkit
Talks to flowgraph through FIFOs
IRA Main Panel
IRA SETI Waterfall
IRA Spectral
IRA Pulsar
IRA Continuum
IRA Interferometer
Typical Total-Power observation Sagittarius A in Total Power Combined multi-day observations
An exciting new project 18M dish at Shirleys Bay
Needs lots of work
SBRAC consortium formed to
renovate/operate for amateur RA
and SETI
Further reading Society of Amateur Radio Astronomers
http://www.radio-astronomy.org
“Radio Astronomy Projects, 3rd ed”, William Lonc
http://www.radiosky.com
National Radio Astronomy Observatory
http://www.nrao.edu
http://www.cv.nrao.edu/course/astr534/ERA.shtml
Radio Jove Project
http://radiojove.gsfc.nasa.gov