Projects: SETI@home
Reobservations
Report No. 4
Results in Real Time
by Amir Alexander
March 17, 2003:
SETI@home scientists will
have to wait for several weeks for the full analysis of the data collected
during the reobservations (see Reobservations
Report no. 2). But even while the observations are going on at Arecibo,
they will already have a good idea if they have found something significant.
This is thanks to SERENDIP IV - the 168 million
channel SETI spectrometer that piggy-backs on the Arecibo radio telescope
throughout the year. As the giant dish scans the skies during the reobservations
from March 18th through the 20th, SERENDIP IV will be processing the data
in real time and telling to Dan Werthimer and his team if they are onto
something interesting. These "real time" results will also help
the SETI@home crew direct the reobservations more effectively. If a certain
candidate signal seems particularly promising, they may decide to spend
some extra time on it even at the expense of other candidates lower down
on the priority scale.
SERENDIP IV has been operating at Arecibo
since June of 1997, when it replaced the earlier 4 million channel spectrometer
SERENDIP III. Like SETI@home, during most of the year it gathers its data
from the SETI receiver at the base of the line feed. During the reobservations,
however, it will be analyzing the data collected by the L Band receiver
located in the Gregorian dome. That is the receiver that will be used
by SETI@home scientists to revisit their most promising candidates.
In some ways, the SERENDIP IV search closely
resembles SETI@home. Both projects look for signals near the hydrogen
line at 1420 MHz, though SETI@home's unlimited computing power allows
for a more sensitive analysis than is possible with SERENDIP. SERENDIP,
however, scans a far wider frequency band around the hydrogen line - 100
MHz as against a mere 2.5 MHz for SETI@home. In fact, since both projects
use the same receiver at Arecibo, the SETI@home data is simply the middle
2.5 MHz of the 100 MHz band analyzed by SERENDIP.
Unlike SETI@home, SERENDIP IV does not record
the raw data collected by the Arecibo receiver. Instead, it processes
it quickly by breaking it down to 168 million channels, each only 0.6
Herz wide. Only significant radio pulses that rise substantially above
the natural background noise of the spectrum are registered and referred
for further analysis.
This makes SERENDIP IV ideally suited
for real time analysis during the reobservations. While detailed analysis
of the data will have to wait, SERENDIP IV will be on the spot, telling
SETI scientists if they are onto something. If a true alien signal is
out there among the 200 candidates, SERENDIP IV will most likely be the
first to know about it.
A Sky Map of SETI@home's Most Promising Candidates
The locations of SETI@home's most promising candidates in the Arecibo sky, during the reobseration sessions March 18-24, 2003. The blue areas mark the plane of the Milky Way Galaxy. The yellow squares mark the locations of the most promising candidates. Created: March 2003.
Credit: Regents of the University of California, SETI@home
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