Sky & Telescope - August 2022 - 39

(InGaAs) detectors - sensitive at 900 to 1700 nanometers -
has made them affordable.
Shelley Wright (University of California, San Diego) and
others used InGaAs sensors to construct the Near-Infrared
and Optical (NIRO) SETI instrument, now on the 1-meter
Anna L. Nickel Telescope at Lick Observatory. Wright's
team designed the system to spot nanosecond-long flashes,
100 million times shorter than the time it takes to blink an
eye. So far, they haven't found any repeating pulses from
1,280 objects, each observed for at least 300 seconds.
Because the small field of view reduces the odds of looking
at the right place at the right time, Wright is now working on
a more ambitious project: Panoramic SETI. Called PanoSETI
for short, the project will ultimately comprise a pair of observatories,
each filled with half-meter telescopes searching the
whole sky for flashes less than a second long.
To test the concept, the team installed two prototype telescopes
at Lick, in the dome that houses the historic Carnegie
Double Astrograph, and tested another two at a temporary
site near Palomar Observatory. Installation at Lick finished
in February 2020, but COVID-19 stalled first light; the group
began testing in March 2021. Wright and her colleagues are
now seeking additional funding and testing observing conditions
at their preferred site on Palomar Mountain in southern
California, the site of the 200-inch Hale Telescope.
In the full-scale installation at Palomar, the two domes,
separated by 1 kilometer, would both contain 45 identical
telescopes, each fixed in place with a 10° × 10° field of view.
As Earth turns, the telescopes will scan 10,000 square degrees
- the whole observable sky. The separation between the two
domes will help rule out false alarms.
Piggybacking
Besides building its own equipment, the SETI Institute has
long borrowed time on other instruments. " Sometimes we
add new instruments, sometimes new sensors, sometimes a
new detector, and sometimes new algorithms, " says Siemion.
With radio telescopes, he adds, " the main thing we need to
do is to bring large computers to [analyze] the data to look for
narrowband radio signals. "
Two technological revolutions occurring in parallel are
proving to be boons for SETI: the development of powerful
radio arrays able to collect vast amounts of data, and
the development of powerful computers able to process that
data. The gigabytes and even terabytes collected daily by big
arrays - including Australia's Murchison Widefield Array, the
27-dish Very Large Array (VLA) in the U.S., and MeerKAT, a
64-antenna South African precursor to the Square Kilometer
Array - would have overwhelmed earlier generations of computers.
But newer processors are capable of not only handling
the data but piggybacking on other astronomical research to
create additional search opportunities. After all, processing
power comes cheaper than brand-new telescopes.
For example, a project called the Commensal Open-Source
Multimode Interferometer Cluster (COSMIC) SETI aims to
Coming Up Empty
Ultimately, what SETI seeks is signals. So,
what happens if we don't find any? Do we
give up? Stop funding SETI?
Similar questions have arisen around other
topics, such as dark matter. Ample indirect
evidence suggests dark matter's presence in
galaxies and clusters, yet the lack of direct
detections troubles many. Nevertheless,
progress continues as scientists conduct
increasingly sensitive searches - and in that
respect, SETI is no different.
In fact, the lack of a signal can be informative
in and of itself, ruling out certain stellar
systems or types of technosignatures. As
just one example, the Breakthrough Listen
team has searched 1,327 nearby stars for the
type of radio signals our own civilization can
make - and found nothing. The survey eliminates
the possibility of both an Earth-directed
radio beacon as well as radio noise from a
human-equivalent civilization. The upper limit
that Danny Price (University of California,
Berkeley) and colleagues derived from this
non-detection? Less than 0.1% of the stellar
systems within 160 light-years possess such
transmitters.
Such experiments will guide future searches
by setting ever more meaningful upper
limits to what's out there. And maybe someday,
they'll narrow the search enough to help
snag a signal from E.T.
- MONICA YOUNG
copy over signals gathered by the VLA for conventional radio
astronomers. A splitter takes the feed from each radio dish
and digitally copies the signals that astronomers are recording
for other purposes. The data then go to SETI's processors,
which can use them to examine other parts of the sky. " Even
though the principal VLA observer might be studying galaxies
or galactic nebulae, " Shostak says, " the SETI scientists can be
studying several nearby star systems as if they had a couple of
large, single-dish antennas at their disposal. "
Looking Forward
The odds against finding alien intelligence may be long, but
that doesn't phase Shostak, Siemion, Wright, and others
involved in SETI projects. They have an enormous universe to
sk yand tele scope .o r g * AUGUST 2022 39
http://www.skyandtelescope.com

Sky & Telescope - August 2022

Table of Contents for the Digital Edition of Sky & Telescope - August 2022

Contents
Sky & Telescope - August 2022 - Cover1
Sky & Telescope - August 2022 - Cover2
Sky & Telescope - August 2022 - 1
Sky & Telescope - August 2022 - Contents
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