Subject: HRMS Update - January 1993
NASA HIGH RESOLUTION MICROWAVE SURVEY (HRMS)
TARGETED SEARCH AND SKY SURVEY STATUS
INAUGURATION + 60 DAYS
The High Resolution Microwave Survey (HRMS) is part of the Toward Other
Planetary Systems (TOPS) program in NASA's Solar System Exploration Division.
The HRMS looks for evidence of planets orbiting other stars through radio
emissions that may be produced by technological civilizations on any such
planets. The HRMS has two search modes, a Sky Survey and a Targeted Search.
The Sky Survey, managed by the Jet Propulsion Laboratory, uses 34-meter
antennas in NASA's Deep Space Network to sweep the entire sky over a wide range
of frequencies for the presence of strong signals. The Targeted Search uses
the largest available radio telescopes to observe nearby sun-like stars over a
narrower range of frequencies for weak signals. The Targeted Search is managed
by NASA's Ames Research Center which is also the lead center for the HRMS. The
combination of the two search modes is millions of times more comprehensive
than the sum of all previous search programs. The observational phase of the
HRMS was inaugurated at 1900 hours Universal Time on 12 October 1992, Columbus
Day, at the NASA Goldstone Deep Space Communications Complex in California and
the Arecibo Observatory in Puerto Rico. The Arecibo Observatory is part of the
National Astronomy and Ionosphere Center, operated by Cornell University for
the National Science Foundation. In a coordinated program, the Arecibo antenna
pointed at the star GL615.1A and the Goldstone antenna began to scan a small
area of sky that included the position of the target star. The beginning of
the search generated world-wide interest in the media. This report presents an
overview of the observations and results to date.
Initial observations began with the new 34-meter antenna at the Venus
Development Station at Goldstone. The project is using the available X-Band
receiver which can be tuned from 8200 to 8600 MHz, and the Sky Survey Prototype
System (SSPS). The SSPS divides 40 MHz of the spectrum into two million 20JHz
channels and automatically looks for Continuous Wave signals as the search
progresses. Each observation involves driving the antenna rapidly in a
"sliding racetrack" pattern programmed to cover a "sky frame," a rectangular
area of sky approximately 1 degree high and 30 degrees in length.
While observing, the SSPS temporarily stores data from channels with power
above a specified threshold level and excises data from channels affected by
terrestrial signals. The scan pattern is designed so that each point in the
frame will be scanned by the antenna at least twice (with slightly different
offsets) at times separated by about 10 minutes. Candidate signals drawn from
the temporary buffer are selected for verification tests at the completion of
the sky frame. A total of 17 sky frames, including 4 repeat frames, have been
observed at X-Band. To date, no candidates have passed the verification tests
and the results are entirely consistent with the expected thermal noise
statistics. Through January 1993, the SSPS will continue to observe about one
day per week on the 34-meter antenna at Goldstone with an increase in allocated
time later in the year.
A special set of three sky frames covering parts of the galactic plane were
observed repeatedly in the frequency bands 1600-1750 MHz and 1380-1430 MHz.
These observations, using the available L-Band receiver on the 26-meter antenna
at the Venus site, are designed to optimize radio astronomy data and improve
interference excision algorithms.
The Targeted Search System (TSS) used the 305-meter antenna of the Arecibo
Observatory, the world's largest, for its initial observations. The TSS
processed a 10 MHz bandwidth into more than 14 million channels simultaneously,
producing parallel channel resolutions ranging from 1 Hz to 28 Hz. Data were
analyzed in real-time for the presence of Continuous Wave (CW) and Pulsed
signals that may drift in frequency by as much as 1 Hz per second.
Observations focused on a list of 25 stars within 100 light years. Receivers
provided by the observatory allowed observations in four frequency bands
covering a total of about 300 MHz within the range from 1300 MHz to 2400 MHz.
Each "observation" of a star in a particular frequency band consisted of three
steps with the antenna first pointed at the star, then away from the star, and
then back at the star. Each observing step lasted either 92 seconds or 299
seconds. Signals that were present only when the telescope was pointed at the
star were considered potentially of extraterrestrial origin and were subjected
to further tests. Signals that were present both "on" and "off" the star were
deemed to be terrestrial interference signals. A total of 436 observations
were conducted during the 200 hours of assigned telescope time. A large number
of interference signals were detected and cataloged. Fifteen signals required
further verification tests but all proved to be intermittent terrestrial
Since returning from Arecibo, the TSS is being reassembled in the TS
development lab at NASA Ames. As expected, operational experience has indicated
the need for modifications to several circuit boards and improvements to the
control software. Over the next year the capability of the system will also be
doubled to cover 20 MHz. This work is in preparation for observations of
nearby sun-like stars in the Southern Hemisphere, scheduled to begin in 1994 at
the 64-meter antenna of the Parkes Observatory in Australia. Parkes is part of
the Australian Telescope National Facility operated by the Commonwealth
Scientific Industrial Research Organization. Analysis of the data collected at
Arecibo is now under way with the goal of developing better techniques for
quickly identifying, classifying, and perhaps even avoiding interference
No signals from beyond our Solar System have been detected yet. Although many
signals have been detected, none appear to originate from a point on the sky as
determined by our observation and verification strategies. Most of the signals
were recognized immediately as terrestrial interference by the software. A few
observations and sky frames detected signals that required verification tests.
Nearly all verification tests have been performed at the site within minutes of
the original detection. A few tests had to be performed on the following day.
No signal passed this level of testing.
The HRMS has successfully inaugurated its observational phase. Both the
Targeted Search and the Sky Survey are using the lessons learned in the initial
observations to improve the hardware, software, and observation techniques of
the HRMS project.
For more information, please contact:
NASA Ames Research Center
Moffett Field, CA 94035-1000
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | email@example.com
| | | | __ \ /| | | | Jet Propulsion Lab |
___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Every once in a while,
/___| | | | ___/ | |/__ /| Pasadena, CA 91109 | try pushing your luck.
|_____|/ |_|/ |_____|/ |
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