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 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 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.

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 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 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