1. Linux, SETI, and Radio Astronomy Marcus Leech
Radio Science Laboratories
Image appears courtesy NRAO/AUI

2. 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

3. 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.

4. 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

5. 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

6. Grote Rebers Dish
Now preserved as historical artefact at NRAO, Green Bank, West Virginia

7. 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 == watts/hz/meter2

8. 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)‏

9. 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
-- using data gathered mostly at Arecibo

10. 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

11. Gnu Radio, SDR, Linux SDR Software Defined Radio GNU 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.

12. 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
Beefy gamers-class PC platform: Q GHz, 8GB memory

13. SDR RA/SETI Software http://www.science-radio-labs.com
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

14. 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.

15. Example GRC flow graph

16. Flowgraphs and GUIs
Lots of different applications built with GNU Radio and various GUI toolkits.
All-mode HF transceiver
RADAR
GPS
Radio Astronomy

17. Gnu Radio Application example

18. IRA Software RA/SETI all-mode receiver Based on XFORMs toolkit
Talks to flowgraph through FIFOs

19. IRA Main Panel

20. IRA SETI Waterfall

21. IRA Spectral

22. IRA Pulsar

23. IRA Continuum

24. IRA Interferometer

25. Typical Total-Power observation
Sagittarius A in Total Power
Combined multi-day observations

26. An exciting new project
18M dish at Shirleys Bay
Needs lots of work
SBRAC consortium formed to renovate/operate for amateur RA and SETI

27. Further reading Society of Amateur Radio Astronomers
“Radio Astronomy Projects, 3rd ed”, William Lonc
National Radio Astronomy Observatory
Radio Jove Project