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