linux, seti, and radio astronomy marcus leech radio science laboratories...
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Linux, SETI, and Radio Astronomy Marcus LeechRadio Science Laboratorieshttp://www.radio-science-labs.comImage appears courtesy NRAO/AUI
What is Radio Astronomy?Astronomy at wavelengths from a few mm to tens of metersVisible light has wavelengths in the region of 500nm, that is, 5.0x10-7 metersFrom 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 AstronomyAbility to resolve fine detail highly dependent on wavelengthA 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 wavelengthBoth use parabolic reflectorsBoth must have a surface that is within 1/10th of wavelength of perfect for maximum efficiency.
History of Radio AstronomyLike much in science, it was discovered accidentallyKarl 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 ScienceJansky was re-assigned to other projects after his work on radio-telephone hiss.Several years went by with nobody understanding the significance of his discoveryGrote 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 1944Radio Astronomy now taken seriously
Grote Rebers DishNow preserved as historical artefact at NRAO, Green Bank, West Virginia
Radio Astronomy TodayRadio Astronomy at the cutting-edge of astrophysical researchRoughly 70% of what we know today about the universe and its dynamics is due to radio astronomy observations, rather than optical observationsBig projects all over the worldVLA, New MexicoArecibo, Puerto RicoGBT, Green Bank, West VirginiaWesterbork, Jodrell Bank, ALMA, Hat Creek, SKA, etcScientists named the basic flux unit after Karl Jansky1 Jansky == 10-26 watts/hz/meter2
SETIDrake equation:N = R* x Fp * Ne x Fl x Fi x Fc x LN number of potential ET civilizationsR* rate of star formationFraction of stellar systems with planetsNe fraction planets that can support lifeFl fraction that actually produce lifeFi Fraction that develop intelligent lifeFc fraction that develop detectable technologies (radio, etc)L length of time such civilizations emit (lifetime)
SETI contdMany observing programs over the yearsHarvard: META and BETASERENDIP I/IINASA: HRMSCancelled after only 1 year by senator Richard BryanThis hopefully will be the end of Martian hunting season at taxpayers expenseWas a comparatively-small NASA programPersonnel went on to form the SETI InstituteSETI@Home -- using data gathered mostly at Arecibo
SETI Science/EngineeringLook 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 spectrometersUsually done in ASIC implementing high-speed FFTSDR can play a role
Gnu Radio, SDR, LinuxSDR Software Defined RadioSoftware to replace traditional hardware functionsFAST A/D and D/A hardwareREALLY FAST compute platformsGNU RadioOpen Source toolkit for SDRCost-effective (like, free) solution for experimental RF/Microwave work.
SDR HardwareProvides basic RF interfaceHigh-speed A/D and D/Adown/upconversion to/from baseband signalsSome digital filteringMany hardware platformsUSRP Universal Software Radio Peripheralhttp://www.ettus.comBeefy gamers-class PC platform: Q6600 3.5GHz, 8GB memory
SDR RA/SETI SoftwareDeveloped gr-radio-astronomy subtree of Gnu RadioProvides basic RA and SETI toolsOpen SourceNew IRA software:Fully integrated RA/SETI receive chainSETI up to 16Million 1Hz channelsPulsar, Total Power, Spectral, Transientshttp://www.science-radio-labs.com
GNU Radio Development ToolsPython and C++ can be used to assemble so-called flow graphs.Signal processing chainGRCGraphical tool to generate flow-graphs, using MATLAB/LabView like interface.
Example GRC flow graph
Flowgraphs and GUIsLots of different applications built with GNU Radio and various GUI toolkits.All-mode HF transceiverRADARGPSRadio Astronomy
Gnu Radio Application example
IRA SoftwareRA/SETI all-mode receiverBased on XFORMs toolkitTalks to flowgraph through FIFOs
IRA Main Panel
IRA SETI Waterfall
Typical Total-Power observationSagittarius A in Total PowerCombined multi-day observations
An exciting new project18M dish at Shirleys BayNeeds lots of workSBRAC consortium formed to renovate/operate for amateur RA and SETI
Further readingSociety of Amateur Radio Astronomershttp://www.radio-astronomy.orgRadio Astronomy Projects, 3rd ed, William Lonchttp://www.radiosky.comNational Radio Astronomy Observatoryhttp://www.nrao.eduhttp://www.cv.nrao.edu/course/astr534/ERA.shtmlRadio Jove Projecthttp://radiojove.gsfc.nasa.gov