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The Search for Extraterrestrial Radio Emissions from Nearby Intelligent Populations |
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SERENDIP Vb Installation ReportDATELINE: Berkeley, California - June 25, 2009During the first few weeks of June 2009, several members of the Berkeley SETI Group and the Center for Astronomy Signal Processing and Electronics Research (CASPER) visited Arecibo Observatory to install a new spectrometer system, SERENDIP Vb. This spectrometer is part of the fifth iteration of the Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations (SERENDIP) project, an effort which began at UC Berkeley in 1978. Over the last 30 years SERENDIP spectrometer development has closely tracked the Moore's Law growth in the electronics industry, with new spectrometers processing ever-larger bandwidths and achieving better and better spectral resolution. Searching large bandwidths is important in the SETI effort, as we can only make guesses at the frequencies where ETIs might transmit electromagnetic signals. High spectral resolution is crucial for distinguishing narrow band astronomical signals from astrophysical and instrumental noise, as well as radio frequency interference. |
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SERENDIP Vb is the most powerful spectrometer yet-built as part of the SERENDIP project. When complete, it will channelize over 2 GHz of instantaneous bandwidth (7 beams x 300 MHz) at less than 2 Hz resolution. All of the SERENDIP searches differ from SETI@home in the key respect that they perform the computationally intensive translation between the time domain to frequency domain (the Fast Fourier Transform) internally, rather than through distributed computing. While SERENDIP spectrometers have phenomenal computation capabilities, they can't come close to matching the number-crunching prowess of the massive supercomputer created by SETI@home volunteers. This forces SERENDIP spectrometers to use much simpler ET search algorithms than SETI@home employs. However, since the SERENDIP spectrometer is sitting in a control room at Arecibo rather than in a volunteers bedroom, it has access to a much larger volume of data or bandwidth. This means that though the SERENDIP spectrometer can't perform all the very complicated algorithms SETI@home can, it can search a much larger swath of the electromagnetic spectrum. Both SERENDIP and SETI@home are thus complementary, in that together they can look with both a panoramic gaze across many MHz and with microscopic precision near the 21cm 'watering hole.' |
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The SERENDIP Vb Spectrometer System is built around the Berkeley Emulation Engine 2 (BEE2) field programmable gate array (FPGA) based computing board. This board provides the combination of data I/O and compute resources necessary to efficiently process wide-band radio astronomy inputs. |
| The SERENDIP Vb Spectrometer System currently takes up around 3/4 of a server rack, but will perhaps expand slightly as we build up the capacity to process all seven Arecibo ALFA beams simultaneously. The SERENDIP Vb team spent the majority of the installation phase connecting SERENDIP Vb interface cables. Making sure the dozens of interconnections between computers, networks and the Arecibo telescope are properly connected requires both patience and attention to detail. |  |
In order to test the SERENDIP Vb spectrometer system, we observed a variety of astronomical sources with both our new instrument, as well as existing spectrometers known to function properly.
Because SETI@home is running commensally all the time, we were able to simultaneously collect data with it as well.
Below is a map of all of the candidates selected for possible observation during SERENDIP Vb engineering testing. The Crab Pulsar was selected as our primary diagnostic because its emission has both well characterized continuum features, for testing the general functionality of the SERENDIP Vb spectrometer, and very short bursts of radiation useful for testing SETI@home's new Astropulse search algorithm.
In addition, we selected several hundred ETI-candidate sources to observe in the event that we had observing time available. Rather than selecting candidates of a single type, for example only stars with known planets or only the closest regions of our galaxy, we selected many different kinds of sources. Just like we don't know what frequency ET might be transmitting on, we also can only guess at the type of environment where ET might live. Thus we try to spread around our valuable telescope time amongst all the possible sources we might observe. For this experiment, we selected previously highly ranked parts of the sky from the SETI@home experiment, highly ranked sources identified by Optical SETI experiments and calm 'habitable' type stars from the Hipparcos Catalog.
Most of the sources below are near the Crab Pulsar, since our engineering time was scheduled such that the Crab Nebula would be directly overhead.
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Candidate identified by SETI@home |  |
Candidate identified by Optical SETI |  |
HabCat Star from the Habitable Stars Catalog |  |
Non-SETI Candidate |  |
Observation Successful |
Planetary Society's excellent article on SETI@home and SERENDIP Vb.
CASPER's technical description of the SERENDIP Vb instrument system.
| Copyright © 2009 University of California |