Jeff Cobb

SETI@home: an experiment in public-resource computing

Millions of computer owners worldwide contribute computer time to the search for extraterrestrial intelligence, performing the largest computation ever.

SETI@home-massively distributed computing for SETI

Starting in the late 1950s, researchers have been performing progressively more sensitive searches for radio signals from extraterrestrial civilizations, but each search has been limited by the technologies available at the time. As radio frequency technologies have became more efficient and computers have become faster, the searches have grown larger and more sensitive, The SETI@home project, managed by a group of researchers at the Space Sciences Laboratory of the University of California, Berkeley, is the first attempt to use large-scale distributed computing to perform a sensitive search for radio signals from extraterrestrial civilizations.

A New Major Seti Project Based on Project Serendip Data and 100,000 Personal Computers

We are now developing an innovative SETI project, tentatively named seti@home, involving massively parallel computation on desktop computers scattered around the world. The public will be uniquely involved in a real scientific project. Individuals will download a screensaver program that will not only provide the usual attractive graphics when their computer is idle, but will also perform sophisticated analysis of SETI data using the host computer. The data are tapped off Project Serendip IVs receiver and SETI survey operating on the 305-meter diameter Arecibo radio telescope. We make a continuous tape-recording of a 2 MHz bandwidth signal centered on the 21 cm HI line. The data on these tapes are then preliminarily screened and parceled out by a server that supplies small chunks of data (50 seconds of 20 kHz bandwidth, a total of 0.25 MB) over the Internet to clients possessing the screen-saver software. After the client computer has automatically analyzed a complete chunk of data (in a much more detailed manner than Serendip normally does) a report on the best candidate signals is sent back to the server, whereupon a new chunk of data is sent out. If 50,000-100,000 customers can be achieved, the computing power will be equivalent to a substantial fraction of a typical supercomputer, and seti@home will cover a comparable volume of parameter space to that of Serendip IV.

New SETI Sky Surveys for Radio Pulses

Berkeley conducts 7 SETI programs at IR, visible and radio wavelengths. Here we review two of the newest e orts, Astropulse and Fly’s Eye. A variety of possible sources of microsecond to millisecond radio pulses have been suggested in the last several decades, among them such exotic events as evaporating primordial black holes, hyper-flares from neutron stars, emissions from cosmic strings or perhaps extraterrestrial civilizations, but to-date few searches have been conducted capable of detecting them. The recent announcement by Lorimer et al. of the detection of a powerful ( 30 Jy) and highly dispersed ( 375 cm 3 pc) radio pulse in Parkes multi-beam survey data has fueled additional interest in such phenomena. We are carrying out two searches in hopes of finding and characterizing these uS to mS time scale dispersed radio pulses. These two observing programs are orthogonal in search space; the Allen Telescope Array’s (ATA) ”Fly’s Eye” experiment observes a 100 square degree field by pointing each 6m ATA antenna in a di erent direction; by contrast, the Astropulse sky survey at Arecibo is extremely sensitive but has 1/3,000 of the instantaneous sky coverage. Astropulse’s multibeam data is transferred via the internet to the computers of millions of volunteers. These computers perform a coherent de-dispersion analysis faster than the fastest available supercomputers and allow us to resolve pulses as short as 400 nS. Overall, the Astropulse survey will be 30 times more sensitive than the best previous searches. Analysis of results from Astropulse is at a very early stage. The Fly’s Eye was successfully installed at the ATA in December of 2007, and to-date approximately 450 hours of observation has been performed. We have detected three pulsars (B0329+54, B0355+54, B0950+08) and six giant pulses from the Crab pulsar in our diagnostic pointing data. We have not yet detected any other convincing bursts of astronomical origin in our survey data.

A 1.1-1.9 GHz SETI Survey of the Kepler Field. I. A Search for Narrow-band Emission from Select Targets

We present a targeted search for narrow-band ( T_(eq) > 230 K, stars with five or more detected candidates or stars with a super-Earth (R_p 50 day orbit. Baseband voltage data across the entire band between 1.1 and 1.9 GHz were recorded at the Robert C. Byrd Green Bank Telescope between 2011 February and April and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than ~1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1 and 2 GHz at an equivalent isotropically radiated power (EIRP) of ~1.5 × 10^(21) erg s^(–1), approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be < 10^(-6) M⊙^(-1). Here we describe our observations, data reduction procedures and results.

Status of the UC-Berkeley SETI efforts

We summarize radio and optical SETI programs based at the University of California, Berkeley. The SEVENDIP optical pulse search looks for ns time scale pulses at visible wavelengths. It utilizes an automated 30 inch telescope, three ultra fast photo multiplier tubes and a coincidence detector. The target list includes F, G, K and M stars, globular cluster and galaxies. The ongoing SERENDIP V.v sky survey searches for radio signals at the 300 meter Arecibo Observatory. The currently installed configuration supports 128 million channels over a 200 MHz bandwidth with ~1.6 Hz spectral resolution. Frequency stepping allows the spectrometer to cover the full 300MHz band of the Arecibo L-band receivers. The final configuration will allow data from all 14 receivers in the Arecibo L-band Focal Array to be monitored simultaneously with over 1.8 billion channels. SETI@home uses the desktop computers of volunteers to analyze over 160 TB of data at taken at Arecibo. Over 6 million volunteers have run SETI@home during its 10 year history. The SETI@home sky survey is 10 times more sensitive than SERENDIP V.v but it covers only a 2.5 MHz band, centered on 1420 MHz. SETI@home searches a much wider parameter space, including 14 octaves of signal bandwidth and 15 octaves of pulse period with Doppler drift corrections from -100 Hz/s to +100 Hz/s. SETI@home is being expanded to analyze data collected during observations of Kepler objects of interest in May 2011. The Astropulse project is the first SETI search for μs time scale pulses in the radio spectrum. Because short pulses are dispersed by the interstellar medium, and the amount of dispersion is unknown, Astropulse must search through 30,000 possible dispersions. Substantial computing power is required to conduct this search, so the project uses volunteers and their personal computers to carry out the computation (using distributed computing similar to SETI@home). Keywords: radio instrumentation, FPGA spectrometers, SETI, optical SETI, Search for Extraterrestrial Intelligence, volunteer computing, radio transients, optical transients.

Far-Ultraviolet Absolute Flux of α Virginis*

We present the far-ultraviolet spectrum of α Virginis taken with Espectrografo Ultravioleta extremo para la Radiacion Difusa (EURD) spectrograph on board MINISAT-01. The spectral range covered is from ~900 to 1080 A with 5 A spectral resolution. We have fitted Kurucz models to IUE spectra of α Vir and compared the extension of the model to our wavelengths with EURD data. This comparison shows that EURD fluxes are consistent with the prediction of the model within ~20%-30%, depending on the reddening assumed. EURD fluxes are consistent with Voyager observations but are ~60% higher than most previous rocket observations of α Vir.

The next phases of SETI@home

Since it’s public release in 1999, the capabilities of SETI@home have grown rapidly. The continuation of Moores law has led to personal computers one thousand times faster than those available in 1999, with graphics processing units that can provide processing speeds only seen on supercomputers in the last century. The capabilities of the SETI@home software have increased to better utilize the available processing power. Increases in radio astronomy instrumentation technologies have also led to improvements in the potential data sources for SETI@home. I will describe the evolution of SETI@home, and how it will change in the future to better match the available technologies, in the data sources, the data processing techniques, and the candidate identification process.

Commissioning of ALFABURST: Initial tests and results

Fast Radio Bursts (FRBs) are apparently one-time, relatively bright radio pulses that have been observed in recent years. The origin of FRBs is currently unknown and many instruments are being built to detect more of these bursts to better characterize their physical properties and identify the source population. ALFABURST is one such instrument. ALFABURST takes advantage of the 7-beam Arecibo L-band Feed Array (ALFA) receiver on the 305-m Arecibo Radio Telescope in Puerto Rico, to detect FRBs in real-time at L-band (1.4 GHz). We present the results of recent on-sky tests and observations undertaken during the commissioning phase of the instrument. ALFABURST is now available for commensal observations with other ALFA projects.

Commissioning and testing of SERENDIP VI instrumentation USNC-URSI national radio science meeting

SERENDIP VI is the sixth installment of the Berkeley SETI Research Centers Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations program, which has been ongoing since 1979. Installed on the Arecibo and Green Bank Telescopes in 2014 and 2015, respectively, this latest version of SERENDIP is currently recording approximately 300 signals per minute. Like its younger sibling project, SETI@home, SERENDIP is a commensal program that piggybacks on other users observations, looking for evidence of narrow-band radio emission from extraterrestrial technologies. SERENDIP VI at Arecibo performs high-resolution (1 Hz) channelization of up to seven 300 MHz bandwidth dual-polarization inputs. SERENDIP VI at GBT performs the same analysis over a single 1.5 GHz dual-polarization input.